NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 7 Control And Coordination, let’s have an overview of topics and subtopics under control and coordination class 10 NCERT questions:

1. Control And Coordination
2. Animals – Nervous System
3. Coordination In Plants
4. Hormones In Animals

Page Number: 119

Question 1
What is the difference between a reflex action and walking?
Answer:

Reflex action	Walking
1. It is the action which is performed automatically.	1. It is a response to the information transmitted by nerve to muscles of the legs. In this case, thinking is involved.
2. It is controlled and coordinated by spinal cord.	2. Brain instructs and controls leg muscles to move.
3. It is an involuntary action.	3. It is a voluntary action.

Question 2
What happens at the synapse between two neurons?
Answer:
The small empty space between two nerve cells is called synapse. At synapse, a chemical substance is produced at the end of axon of one nerve cell that reaches to the other nerve cell through the dendrite. Thus, information is transmitted from one nerve cell to other nerve cell by synapse.

Question 3
Which part of the brain maintains posture and equilibrium of the body ?
Answer:
Posture and equilibrium of the body are controlled by cerebellum.

Question 4
How do we detect the smell of an agarbatti (incense stick) ?
Answer:
The smell of agarbatti (incense stick) diffuses in the air. It is detected by olfactory receptors present in the nose. This information is sent to olfactory lobe by sensory nerves located in the forebrain. It responds to the information.

Question 5
What is the role of the brain in reflex action ?
Answer:
There is no role of brain in reflex action. These involuntary actions are controlled by the spinal cord which take place immediately without thinking of how to respond to the stimuli.

Page Number: 122

Question 1
What are plant hormones ?
Answer:
Plant hormones are also called phytohormones. Plant hormones are the chemical substances which help in controlling growth, flowering, height, development of plants and their response to the environment.

Different types of phytohormones are – auxins, gibberllins, cytokinins, abscisic acid and ethylene.

Question 2
How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light ?
Answer:

Movement of leaves of sensitive plant	Movement of a shoot towards light
1. It is a nastic movement which does not depend on the direction of stimulus applied.	1. It is a tropic movement which depends on the direction of stimulus applied.
2. The stimulus is touch.	2. The stimulus is light.
3. It is caused by the sudden loss of water from the swellings at the base of leaves.	3. It is caused by the unequal growth on the two sides of the shoot.
4. It is not a growth movement.	4. It is a growth movement.

Question 3

Give an example of a plant hormone that promotes growth.
Answer:
Auxin.

Question 4
How do auxins promote the growth of a tendril around a support ?
Answer:
When the tip of a tendril touches a support, then the auxins present in its tip move to that side of tip which is away from the support. Auxins promote growth. So, due to more auxins in it, the side of tendril away from the support grows faster (and becomes longer) than the side which is in contact with the support and makes the tendril twirl (or bend) around the support.

Question 5
Design an experiment to demonstrate hydrotropism.
Answer:
Take two glass troughs A and B and fill each one of them two-thirds with soil. In trough A plant a tiny seedling. In trough B plant a similar seedling and place a c/ay pot inside the soil. Water the soil in trough A daily and uniformly. Do not water the soil in trough B but put some water in the clay pot. Leave both the troughs for a few days.

Now, dig up the seedlings carefully from both the troughs without damaging their roots. We will find that the root of seedling in trough A is straight. On the other hand, the root of seedling in trough B is found to be bent to the right side i.e., towards the clay pot containing water.
In trough A, the root of the seedling gets water from both sides. But in trough B, the roots get water oozing out from the clay pot which is kept on the right side. Therefore, the root of seedling in trough B grows and bends towards the source of water to the right side. This experiment shows that the root of a plant grows towards water. In other words, the root of a plant is hydrotropism.

Page Number: 125

Question 1
How does chemical coordination take place in animals ?
Answer:
Chemical coordination in animals takes place through the hormones secreted by the endocrine glands. Coordination in animals takes place through hormone system as well as nervous system which is called endocrine system. Endocrine glands secrete animal hormones directly into the blood that reach to the specific cells. Special type of molecules are present on the surface of cells to detect these hormones. These cells act according to the information that a particular hormone carries.

Question 2
Why is the use of iodised salt advisable ?
Answer:
It is advised to use iodised salt because thyroid gland needs iodine to produce thyroxin hormone. Thyroxin hormone controls all the metabolic activities of our body like metabolism of carbohydrates, fats and protein etc. Due to the deficiency of thyroxin a disease called goitre is caused.

Question 3
How does our body respond when adrenaline is secreted into the blood ?
Answer:
The heart beat increases when adrenaline is secreted into the blood so that more oxygen is supplied to our muscles. The blood supply to the digestive system and skin decreases because the small arteries around the muscles of these organs contract. This turns the direction of blood towards our skeletal muscles. The breathing rate also increases due to the contractions of the diaphragm and rib muscles. All these responses enable us to face the situations of fear and anger.

Question 4
Why are some patients of diabetes treated by giving injections of insulin ?
Answer:
Insulin hormone regulates blood sugar levels. If this is not secreted in proper amounts, the sugar level in the blood rises. This causes many harmful effects.
To treat harmful effects of increased level of blood sugar, the diabetic patients are treated by giving injections of insulin.

NCERT Solutions for Class 10 Science Chapter 7 Textbook Chapter End Questions

Question 1
Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Answer:
(d) Cytokinin

Question 2
The gap between two neurons is called a
(a) dendrite
(b) synapse
(c) axon
(d) impulse
Answer:
(b) Synapse

Question 3
The brain is responsible for
(a) thinking
(b) regulating the heart beat
(c) balancing the body
(d) all of the above
Answer:
(b) All of the above

Question 4
What is the function of receptors in our body ? Think of situations where receptors do not work properly. What problems are likely to arise ? [AICBSE 2016]
Answer:
Receptors are specialised cells located in our sense organs like ear, nose, skin, tongue and eyes. The function of receptors is to detect information from the environment. For example, olfactory receptors detect smell. If receptors do not work properly, the information obtained from the environment will be delayed to reach the spinal cord or brain. In this situation, the response to the environmental stimulus will be delayed causing harm to the body. For example, if skin receptors are damaged, and one accidentally touches a hot object, then his/her hands might get burn as the damaged receptor cannot perceive the external stimuli of heat and pain.

Question 5
Draw the structure of a neuron and explain its function. [AICBSE 2017]
Answer:
Nerve cell or neuron is the functional unit of nervous system. A nerve cell has three parts-
(i) cell body
(ii) dendrite
(iii) axon

Function : The function of nerve cells is to carry information in the form of electrical signals which are called nerve impulses. Cells receive stimulus to send it to spinal cord and brain and carry the message from brain to the target organ.

Question 6
How does phototropism occur in plants ?
Answer:
The movement in any part of a plant due to light is called phototropism. The shoot of plant shows positive phototropism and roots show negative phototropism.
Phototropism in plants occurs due to the hormone auxin. When light falls on one side of a plant, the secretion of auxin hormone is more in the part away from the light. Hence, auxin causes growth in length of the cells in shady part. So, the plant appears to bend towards light.

Question 7
Which signals will get disrupted in case of a spinal cord injury ?
Answer:
(i) All the involuntary actions will get disturbed.
(ii) Reflex actions will be disturbed because reflexes are located in the spinal cord. Therefore, the quick responses required to safe guard the body will not take place.

Question 8
How does chemical coordination occur in plants ?
Answer:
Chemical coordination in plants takes place with the help of plant hormones. In most of the regions where division takes place (meristematic regions) stimuli cells secrete chemical compounds (hormone). These substances identify the information by stimulating the other nearby cells and communicating the information.

Question 9
What is the need for a system of control and coordination in an organism ?
Answer:
An organism needs control and coordination system for the following functions :
(i) To save the body of the organisms from the harmful changes in the environment.
(ii) To control the speed of voluntary and involuntary actions.
(iii) To have the capability to think and learn for responding to any stimuli.

Question 10
How are involuntary actions and reflex actions different from each other ?
Answer:

Involuntary actions	Reflex actions
1. Those actions which occur immediately without any thinking are called involuntary actions.	1. Reflex action is an immediate response to an event which does not require any processing by brain.
2. Involuntary actions are controlled by mid and hind brain. Example: Breathing, beating of heart, etc.	2. Reflex actions are controlled by spinal cord. Example: Sneezing, coughing, etc.

Question 11
Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Answer:

Nervous mechanism	Hormonal mechanism
It is a fast process.	It is a slow process.
Arteries and glands are affected.	It affects the target organ.
It transmits in electrochemical form.	It transmits in chemical form.
It does not control metabolism.	It controls metabolism.
Growth is not affected.	Growth is affected.

Question 12
What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs ?
Answer:

Movement in a sensitive (mimosa) plant	Movement in legs of a human
1. The leaves of a sensitive plant like mimosa are sensitive to touch.	1. Leg is in control of nerve muscles.
2. It is not controlled by any part of the plant.	2. It is controlled by brain and spinal cord.
3. In this, cells change their shape on changing the amount of water in them.	3. Amount of water has no effect on the movement of muscles.
changing the amount of water in them.	the movement of muscles.
4. The movement in a sensitive plant are nastic movement.	4. The movement in our leg is due to voluntary nervous system.

Control and Coordination Class 10 HOTS

Question 1.
What type of plant movement is seen in the diagram of coiling of tendril?

Or

How do auxins promote the growth of a tendril around a support? Describe in brief. (CCE 2012)
Answer:
Thigmotropism or curvature movement that occurs in response to contact. Less auxin is present in the region of contact. The free side having more auxin shows more growth. This causes the tendril to coil over the support.

Question 2.
Identify and label the parts shown as A and B in the accompanying figure.

Answer:
Dorsal view of thyroid an parathyroid.
A – Thyroid,
B- Parathyroid.

Question 3.
What are the hormones involved in providing milk to the suckling infant ?
Answer:
1. Prolactin (Maternity Hormone). Production of milk.
2. Oxytocin Ejection of milk.

Question 4.
How does pancreas control glucose level of blood ?
Answer:
Pancreas produces two hormones

1. Insulin from P-cells of islet of Langerhans and
2. Glucagon from a- cells of islets of langerhans.

Insulin is produced when glucose level of blood rises. Insulin helps the cells to withdraw glucose from blood. It also converts glucose into glycogen in liver and muscles.

Question 5.
Glucagon is secreted when glucose level of blood falls. It mobilises reserve food like glycogen into glucose. What is pregnancy hormone ? Why is it known so ?
Answer:
Progesterone is called pregnancy hormone. It helps in maintaining pregnancy by non-formation of new ova, promoting thickening and secretory activity of uterine wall and attachment of embryo to the uterine wall.

Question 6.
What is dormin ?
Answer:
Dormin is the other name of plant hormone abscisic acid. The hormne induces dormancy in buds and seeds. So it has been called dormin.

Question 7.
(a)

1. Name the parts labelled A and B in the neuron drawn above.
2. Which part acquires the information in the neuron ?
   
3. Through which part does the information travel ?
4. In what form does this information travel ?
5. Where is the impulse converted into a chemical signal for onward transmission ?

(b) Name the hormone secreted by thyroid. What is the function ?
(c) Why is the use of iodised salt advisable ?
(CBSE A.I. 2008 Compt.)
Answer:
(a)

1. A-Dendrite, B-Axon
2. Dandrite.
3. Dandrite to cell body or cyton to axon.
4. Electrical impulse
5. In the region of synapse.

Impulse stimulates the release of chemical neurotransmitter from the surface of presynaptic knob or bouton of axon terminal. Neurotransmitter (e.g. acetylcholine) comes in contact with chemoreceptor sites of post-synaptic membrane of the next neuron and generates a fresh impulse.

(b) Thyroxine:
Function of Thyroxine. It controls

1. Basal metabolic rate
2. Metabalism of carbohydrates, fats and proteins
3. Consumption of energy in physical activity and body temperature
4. Development and differentiation.

(c) Iodised Salt: Salt is iodised to provide iodine to thyroid for synthesis of thyroxine which is iodine containing hormone.

Question 8.
(a) What are plant hormones ? Give one example each of a plant hormone that

1. promotes growth
2. inhibits growth.
3. promotes cell division
4. promotes the growth of a tendril around a support. (CCE 2011)

(b) Name the parts labelled A, B and C in the diagram given below. Write one function of each part. (CBSE A.I. 2008 Comptt. Delhi 2008 Comptt.)

Answer:
(a) Plant Hormones:
Phytohormones are chemical substances other than nutrients produced naturally in plants which regulate growth, development, differentiation and a number of physiological processes, e.g., auxin, gibberellins, abscisic acid, cytokinins.

1. Hormone That Promotes Growth. Auxin/Gibberellin.
2. Hormone That Inhibits Growth. Abscisic acid or ABA
3. Hormone That Promotes Cell Division. Cytokinin.
4. Hormone That Promotes Growth of a Tendril Around a Support. Auxin.

(b) A-Pons Function: Relay centre, pneumotaxic area of respiratory centre.
B-Medulla Function: Reflex centre, cardiac centre, respiratory centre.
C-Cerebellum Function: Maintains equilibrium and coordinates muscular activities

Control and Coordination Class 10 Value Based Questions

Question 1.
How do tendrils reach the support when they do not have any sensory structures.
Answer:
Tendrils do not have any sensory structures but still they are able to find their support just as we grope in the dark for finding the switch-board. Tendrils perform circumnutation from their apical regions. In this the terminal parts of tendrils move in all directions. Wherever they come in contact with a support, they stop performing cicumnutation. Instead, the contacted region shows little growth while the other side grows rapidly so that the tendril coils over the support.

Question 2.
Name the nervous system which controls the functioning of internal organs. How does this system work ?
Answer:
Autonomous or visceral nervous system. The system does not consult the will of the individual. It works on its own inputs. Autonomous nervous system consists of only motor nerve fibres that innervate all organs and glands of the body. Depending upon the input, autonomous nervous system stimulates, slows down or stops the activity of an organ. For its working, autonomous or visceral nervous system has two components, sympathetic and parasympathetic. Sympathetic nervous system originates from thoracico-lumbar region, forms two ganglionic chains which send out long nerve fibres to various organs. The sympathetic nerve fibres activate the organs by release of nor-adrenaline. Parasympathetic nervous system is called cranio-sacral as it originates from some cranial and sacral nerves. It has long preganglionic fibres and ganglia attached to organs that are innervated. Its post ganglionic fibres secrete acetylcholine into organs for moderating or reducing their activity.

Question 3.
Which system is working when you start sweating during exercise ? What is its function ?
Answer:
Reflex activity of the nervous system. Actually 90% of nervous activity is performed through reflexes. It is automatic, involuntary and spontaneous response to a stimulus without consulting the will of the individual. Exercise increases body temperature. This can be harmful. Reflex action stimulates the sweat glands for releasing their secretion. Part of the sweat evaporates and cools, down the body.

Question 4.
You can become moody by simply switching on night bulb daily. How can this happen ?
Answer:
Night bulb reduces the secretion of melatonin hormone. Melatonin controls our day-night or circadian rhythm, healthy digestive and immune system, sexual cycle and moods. A reduced secretion causes insomnia and mood changes besides affecting health of our digestive and immune system.

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

Control and co-ordination in animals and plants: Tropic movements in plants; Introduction to plant hormones; Control and co-ordination in animals, nervous system; voluntary, involuntary and reflex action; Chemical co-ordination: animal hormones.

Question 1
What is the function of receptors in our body?
Solution:
Receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell.

Question 2
Draw the structure of neuron and explain its function.
Solution:

The specialised tips of some nerve cells detect all information from our environment. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell. This information, acquired at the end of the dendritic tip of a nerve cell, sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. This is a general scheme of how nervous impulses travel in the body. A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland. It is thus no surprise that nervous tissue is made up of an organized network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.

Question 3
How does phototropism occur in plants?
Solution:

Phototropism is a growth movement induced by a light stimulus. Growth towards a source of light is called positive phototropism, that away from the source is termed negative phototropism. The tips of shoots are usually positively, that of roots negatively phototropic.
Charles Darwin and his son Francis discovered (in 1880) that the phototropic stimulus is detected at the tip of the plant.
The Darwins used grass seedlings for some of their experiments. When grass seeds germinate, the primary leaf pierces the seed coverings and the soil while protected by the coleoptile, a hollow, cylindrical sheath that surrounds it. Once the seedling has grown above the surface, the coleoptile stops growing and the primary leaf pierces it.
The Darwins found that the tip of the coleoptile was necessary for phototropism but that the bending takes place in the region below the tip.
If they placed an opaque cover over the tip, phototropism failed to occur even though the rest of the coleoptile was illuminated from one side.
However, when they buried the plant in fine black sand so that only its tip was exposed, there was no interference with the tropism – the buried coleoptile bent in the direction of the light.
From these experiments, it seemed clear that

• The stimulus (light) was detected at one location (the tip)
• The response (bending) was carried out at another (the region of elongation).
• This implied that the tip was, in some way, communicating with the cells of the region of elongation.

Question 4
How does chemical coordination occur in plants?
Solution:
It has been found that the growth of plants is regulated by certain chemical substances which are synthesized by the plants in very small amounts. These are known as plant hormones or phytohormones.

They are the organic substances which either promote or inhibit growth. A phytohormones can be defined as a chemical substances which are produced naturally in plants and are capable of translocation and regulating one or more physiological processes when present in low concentration. Main categories of plant hormones are:

1. Auxins
2. Gibberellins
3. Cytokinins
4. Ethylene
5. Abscisic acid

Auxins and Gibberellins stimulate cell elongations, cytokinins stimulate cell division ethylene promotes transverse or isodiametric growth and abscisic acid is a growth inhibitor.

Question 5
What is the need for a system of control and coordination in an organism?
Solution:
Co-ordination in this sense refers to the regulation or control of body activity.
Plants need very little in the way of a control system. Since growth and reproduction are about the only things that are regulated, a rapid control system is not required and hormonal control is all they possess.

Animals are continually moving through new environments that may pose all types of changes and threatening situations to the organism. This requires the rapid and precise control of a nervous system. Hormones regulate slower activities, such as growth, development and reproduction.

Question 6
How are involuntary actions and reflex actions different from each other?
Solution:
All reflex actions are involuntary in nature but all involutary actions are not reflexes as the beating of heart is an involuntary action but is not reflex action.

Reflex actions are very quick but all involutary actions may not be very fast as in heart beating.
A reflex action may involve any muscle or a gland as we withdraw our hand on touching a hot object but all involuntary actions involve only smooth i.e., involuntary or cardiac muscles.

Reflex actions are at the level of spinal cord whereas the involuntary actions generally involve brain too.
Nerves and autonomious nervous system can increase or decrease the rate of involuntary actions but reflex actions can be controlled by great will only and are not usually controllable.

Reflex actions are done to meet emergencies where as an inv.action may or may not be for just meeting an emergency but may be a critical lie process as circulation of blood, swallowing of food, movement of food in food pipe, etc.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
What is the correct direction of flow of electrical impulses ? [NCERT Exemplar]

Answer:
(c) Direction of flow of electrical impulse.
Impulse → Dendrite → Cell body → Axon → Release of chemicals that cross synapse → Dendrite of next neuron.

Question 2.
Three directions in which nerve impulses can travel in the nervous system are listed below:
(i) Away from the central nervous system
(ii) Towards the central nervous system
(iii) Within the central nervous system
In which direction do impulses in sensory and relay (intermediate) neurons travel?

	Sensory Neuron	Relay Neuron
(a)	(i)	(ii)
(b)	(i)	(iii)
(c)	(ii)	(i)
(d)	(ii)	(iii)

Answer:
(d) Sensory neuron transmits impulses towards CNS, (i.e. brain and spinal cord) while, the relay neurons occur within the CNS and serve as links between other neurons.

Question 3.
In a nerve pathway, the following events take place in a coordinated order.
(i) Activation of muscle
(ii) Activation of receptor
(iii) Passage of impulses along a motor neuron
(iv) Passage of impulses along a sensory neuron
Read the events given and identify the correct order of these events from the table given below:

First	→		Last
(a)	(ii)	(iii)	(iv)	(i)
(b)	(ii)	(iv)	(iii)	(i)
(c)	(iv)	(i)	(iii)	(ii)
(d)	(iv)	(ii)	(i)	(iii)

Answer:
(b) The sequence of events in a typical nerve pathway is receptor → passage of impulse along sensory neuron → passage of impulse along motor neuron →  activation of muscle (effector). Thus, the correct sequence is (ii), (iv), (iii) and (i).

Question 4.
The diagram shows a section of the brain and different parts labelled as W,X, Y and Z.

Study the figure and correlate the regions which control balance, heart rate and temperature in human body?

	Balance	Heart Rate	Temperature
(a)	W	Z	X
(b)	X	Y	Z
(c)	Y	X	W
(d)	Z	W	Y

Answer:
(b) Out of the options given, the region X, (i.e. cerebellum) controls balance, region Y (i.e. medulla oblongata) controls heartbeat and region Z, (i.e. hypothalamus) controls temperature in human body.

Question 5.
Which of the following endocrine glands is unpaired? [NCERT Exemplar]
(a) Adrenal
(b) Testes
(b) Pituitary
(d) Ovary
Answer:
(c) There are two adrenal glands, one on top of each kidney that make adrenaline hormone. Testes are paired glands present in males and secrete male sex hormone. Pituitary gland is present just below the brain and is unpaired. It is also called master gland as it secretes a number of hormones. Ovaries are paired glands present in females and secrete female sex hormones.

Question 6.
Dramatic changes of body features associated with puberty are mainly because of secretion of [NCERT Exemplar]
(a) oestrogen from testes and testosterone from ovary
(b) oestrogen from adrenal gland and testosterone from pituitary gland
(c) testosterone from testes and oestrogen from ovary
(d) testosterone from thyroid gland and oestrogen from pituitary gland
Answer:
(c)

Gland	Hormone		Function
Testes (only in males)	Testosterone		To control the development of male sex organs and male features such as deep voice, etc., i.e. changes associated with puberty.
Ovaries (only in females)	Oestrogen		To control the development of female sex organs and female features such as soft skin, etc.
	Progesterone	To control uterus changes during menstrual cycle and helps in maintenance of pregnancy.

Class 10 Science Control and Coordination Mind Map

Coordination is the process through which two or more organs interact and complement the functions of one another. The neural system & endocrine system jointly coordinate & regulate the physiological functions in the body. The neural system provides an organised network of point-to-point connections for a quick coordination. The endocrine system provides chemical integration through hormones.

Animal Nervous System
The neural system of all animals is composed of highly specialized cells called neurons which can detect, receive & transmit different kinds of stimuli. They are specialized for conducting information via electrical impulses from one part of the body to another.

Structure and Function of Neuron

• It is a structural & functional unit of neural system and is composed of three major parts:
• Ceil body contains cytoplasm with typical cell organelles like nucleus etc.
• Dendrites: Short fibres which branch repeatedly & project out of the cell body. These fibres transmit impulses towards the cell body.
• Axon is a long fibre, the distal end of which is branched and forms nerve ending. Nerve endings possess synaptic vesicles containing chemicals called neurotransmitters.

Transmission of impulses:

• Stimulus or information from the environment is detected by specialized tips of some nerve cells called as receptors.
• Dendritic tip acquire all these information and sets off a chemical reaction.
• This chemical reaction then creates an electric impulse that travels from the dendrite to the cell body, and then along the axon to its end.
• At the end of the axon, the electrical impulse sets off the release of some chemicals (neurotransmitters). These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron.
• A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland.

The human neural system is divided into two parts:

• Central neural system (CNS) includes the brain & spinal cord and is the site of information processing & control.
• Peripheral neural system (PNS) comprises of all nerves of body associated with CNS (brain and spinal cord). The nerve fibres of PNS are of two types: cranial nerves (arising from the brain) and spinal nerves (arising from the spinal cord).

Brain

• It is the main coordinating centre of the body. The bra in and spinal cord constitute the CNS. They receive information from al 1 parts of the body and integrate it.
• The brain is located in bony box called as cranium or skull which protects the brain. Spinal cord is protected with the help of vertebral column. In addition, cerebrospinal fluid also covers the brain and the spinal cord which provide the function of shock absorption.
• The brain has three such major parts or regions, namely the fore-brain, mid-brain and hind-brain.
• Fore-brain: It is the main thinking part of the brain. It consists of cerebrum, hypothalamus etc.
  • Function: interpret information received from sensory receptors.
  • Control the movement of voluntary muscles.
  • It also contains centre associated with hunger which gives us the sensation of feeling full.
• Midbrain: It serves important function in few involuntary movements, movements of the eye, auditory and visual processing.
• Hindbrain: It consists of pons, medulla, and cerebellum.
  • Function: Medulla controls involuntary actions such as blood pressure, salivation and vomiting.
  • Cerebellum is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

Reflex Action

• The entire process of response to a peripheral nervous stimulation that occurs involuntarily (without conscious effort or thought) and requires the involvement of a part of central nervous system is called a reflex action.
• Reflex action decreases the duration of action by bypassing the thinking and processing step.
• It does so by linking the nerves carrying the signal (say the sensation of heat) directly to the nerves that move the muscle. These types of linkage or connection between input and output nerves are formed in the spinal cord.
• These connections are called as reflex arc (sensory/input nerve-* Spinal cord -> motor/ output nerve)

Coordination In Plants

Plants have neither nervous system nor muscles. Their movements or responses are either growth dependent or growth independent.

Immediate Response To Stimulus Or Growth Independent

The plants also use electrical-chemical means to convey information from cell to cell, but unlike in animals, there is no specialised tissue in plants for the conduction of information.

Secondly, plant cells change shape by changing the amount of water in them, resulting in swelling or shrinking. In contrast, animal muscle cells have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses.

Example: folding up and drooping of leaves of chhui-mui (the ‘sensitive’ or ‘touch-me-not’ plant of the Mimosa family) in response to touch.

Movement Due To Growth

The movement of a plant in response to the stimulus is called as tropism. The movement in the direction of the response is called as positive tropism and movement away from the stimulus is termed as negative tropism.

Types:

• Phototropism: Bending of plant in response to the light e.g. movement of sunflowers in response to day or night.
• Geotropism: Movement of plant in response to gravity. Shoots show negative geotropism and roots show positive geotropism.
• Chemotropism: Movement of plant in response to chemical as observed in case of growth of pollen tube.
• Hydrotropism: e.g. roots beneath the Earth’s surface bend in the direction of underground w^ater.
  Other example may include the climbing of tendrils in response to touch. When they come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This causes the tendril to circle around the object and thus cling to it.

Plant Hormones

There are five main types of plant hormones or growth regulators:

• Auxins: Helps in cell elongation and thus phototropism, geotropism, and other plant responses.
• Gibberellins: Stimulate growth of the stem and flowering.
• Cytokinins: They cause cell division, enlargement, and organ formation. They are present in greater concentration in areas of rapid cell division, such as in fruits and seeds.
• Ethylene: Promotes ripening of fruits.
• Abscisic acid: Inhibits growth and causes wilting of leaves and fruits.

Hormones In Animals

Hormones are non-nutrient chemicals which act as intercellular messengers & are produced in trace amounts. The timing and amount of hormone released are regulated by feedback mechanisms Examples:

• Adrenaline: Secreted from adrenal gland which prepare the body for fight or flight situation.
• Thyroxin: Secreted from thyroid gland and regulates carbohydrate, protein and fat metabolism so as to provide the best balance for growth.
  Deficiency of iodine in diet may cause hypo-secretion of thyroxin which results in goiter.
• Growth hormones which regulate growth and. development of the body are secreted from
  pituitary gland.
  Hyper-secretion may cause gigantism and hypo-secretion may cause dwarfism.
• Testosterone in males and oestrogen in females lead to changes take place during puberty’.
• Insulin produced by pancreas regulates the blood sugar level in the body.

NCERT Exemplar Solutions for Class 10 Science Chapter 7 Short Answer Questions

Question 1.

1. Label the parts a, b, c and d and show the direction of electrical signals in the figure. (CBSE 2010)
   
2. Draw the figure shown here and label motor neuron, relay neuron and spinal cord. What is the name of this connection ?
   (CCE 2011)

Answer:

1. a – Sensory neuron.
   b – Spinal cord (CNS).
   c – Mortor neuron.
   d – Effector (muscle in arm)
2. Name — Reflex arc.
   Direction : 
   1. Receptor (hand) to spinal cord through sensory neuron,
   2. Sensory neuron to motor neuron through Spinal cord to effector through motor neuron.

Question 2.
Name the plant hormone responsible for the following :
(a) Elongation of cells
(b) Growth of stem
(c) Promotion of cell division
(d) Falling of senescent leaves.
Answer:
(a) Elongation of Cells. Auxin.
(b) Growth of Stem. Gibberellin.
(c) Promotion of Cell Division. Cytokinin.
(d) Falling of Senescent Leaves. Abscisic acid.

Question 3.
Label the endocrine glands in the figure

Answer:
a – Pineal gland.
b – Pituitary gland.
c – Thyroid
d – Thymus.

Question 4.
In the figures (a), (b) and (c) which appears more accurate and why ?

Answer:
Figure (a) is more accurate as it shows appropriate response of both shoot and root to the vector of gravity. Shoot is negatively geotropic. It, therefore, bends upwardly. Root is positively geotropic. It, therefore, bends downwardly.

Question 5.
Label the parts of a neuron shown in the figure.

Answer:
a – Dendrite.
b – Cyton (Cell body).
c – Axon.
d – Axon terminal (bouton).

Question 6.
Match the terms of column A with those of column B.

A	B
(a)   Olfactory receptors (b)  Thermoreceptors (temperature receptors) (c)  Gustatoreceptors (d)  Photoreceptors	(I) Tongue (ii) Eye (iiî) Nose (iv) Skin

 

Answer:
a – IIi,
b — iv,
c — i,
d — ii.

Question 7.
What is a tropic movement ? Explain with an example. (CCE 2011)
Answer:
Tropic Movement: It is directional paratonie growth movement of curvature in which direction of movement is determined by the direction of the stimulus. They mostly occur in cylindrical organs. Growth response occurs due to differences in the distribution of auxin.
Example. On unidirectional exposure to light, shoots bend towards the source of light (positive phototropism) while roots may bend away from the source of light (negative phototropism).

Question 8.
What will happen if intake of iodine in our diet is low ?
Answer:

1. Low intake of iodine will affect production of thyroxine. Reduced thyroxine reduces metabolism of protein, carbohydrate and fat. Physical activity and consumption of energy are impaired.
2. With continued reduced intake of iodine, thyroid gland enlarges (in order to produce more thyroxine). It results in swelling of neck called goitre.

Question 9.
What happens at the synapse between the neurons ?

                                                   Or

State the events in sequence that take place when an electrical impulse travels from a dendritic tip of a nerve cell to another nerve cell. (CCE 2011, 2012, 2013)
Answer:
At synapse, axon terminal is expanded to form presynaptic knob. The dendrite terminal that lies close to it is slightly broadened and depreseed to form post-synaptic depression. A fluid filled narrow space, called synaptic cleft, occurs between the two. When an impulse reaches the presynaptic knob, it stimulates the release of neurotransmitter into synaptic cleft. Neurotransmitter comes in contact with chemoreceptor sites of the membrane of postsynaptic depression. This generates an electrochemical signal or impulse in the dendrite part of second neuron.

Question 10.
Answer the following :
(a) Which hormone is responsible for the changes noticed in female at puberty ?
(b) Dwarfism results due to deficiency of which hormone ?
(c) Blood sugar level rises due to deficiency of which hormone ?
(d) Iodine is necessary for synthesis of which hormone ?
Answer:
(a) Puberty Changes in Females. Oestrogen.
(b) Dwarfism. Growth hormone.
(c) Blood Sugar. Insulin.
(d) Iodine Hormone. Thyroxine

Question 11.
Answer the following :
(a) Name the endocrine gland associated with brain.
(b) Which gland secrets digestive enzymes as well as hormones ?
(c) Name the endocrine gland associated with kidney.
(d) Which endocrine gland is present in males but not in females ?
Answer:
(a) Endocrine Gland Associated with Brain. Pituitary.
(b) Gland with Digestive Enzymes and Hormones. Pancreas.
(c) Endocrine Gland Associated with Kidneys. Adrenal glands.
(d) Endocrine Gland in Males only. Testis.

NCERT Exemplar Solutions for Class 10 Science Chapter 7 Long Answer Questions

Question 12.
Draw the structure of a neuron and explain its function. (CCE 2011)
Answer:

Functions:

1. Dendrites: Picking up sensations and transmitting the same to cell body.
2. Cell Body:
   1. Sustaining structure and function of dendrites and axon,
   2. Functioning as passage¬way for transmission of sensation or impulse to axon.
3. Axon: Carrying impulse to another neuron, muscle, gland and organ. A single impulse can be transmitted to several structures with the help of axon terminals.

Question 13.
What are the major parts of the brain ? Mention the function of different parts.
Answer:
Major Parts of Brain
Fore-Brain: Olfactory lobes (2), Cerebral hemispheres (2) or cerebrum, Diencephalon.
Mid-Brain: Cerebral peduncles, Corpora quadrigemina.
Hind Brain: Pons, Cerebellum, Medulla oblongata.
Functions

1. Olfactory Lobes: Receive sensation of smell from olfactory epithelium and relay the same to temporal lobes of cerebral hemispheres.
2. Cerebral Hemispheres:
   1. Frontal Lobes: Centres of intelligence, control of movements and facial muscles, speech.
   2. Parietal Lobes: Taste and cutaneous sensations with some components of speech.
   3. Temporal Lobes: Hearing, smell, recall of audiovisual memory, some components of speech.
   4. Occipital Lobes: Sight.
3. Diencephalon: Hypothalamus part regulates activity of smooth muscles and functions as control centre for hunger, thirst, fatigue, sleep, sweating, temperature and emotions. Pituitary gland and pineal gland are components of diencephalon.
4. Corpora Quadrigemina: Superior – sight reflexes. Inferior – auditory reflexes.
5. Cerebellum: Controls posture and equilibrium.
6. Pons: Part of respiratory centre.
7. Medulla Oblongata: Centre for reflexes, blood pressure, heart beat, breathing.

Question 14.
What constitutes the central and peripheral nervous systems ? How are the components of central nervous system protected?
(CCE 2012)
Answer:
Central Nervous System (CNS): It is hollowed part of nervous system that lies along the mid-dorsal part of the body. It has two parts, brain (located in the head) and spinal cord (located in the trunk).
Peripheral Nervous System (PNS): It is soild lateral part of nervous system that develops from CNS and connects different parts of the body with CNS. Peripheral nervous system has two components, voluntary and involuntary. Voluntary peripheral nerous system is under the control of will. It consists of cranial nerves from brain and spinal nerves from spinal cord. Involuntary peripheral nervous system works independent of will. It develops from some cranial and spinal nerves. Involuntary peripheral nervous system is also called autonomic nervous system. It has two parts, sympathetic (for emergency) and parasympathetic (for moderation). They control the functioning of various internal body parts.
Protection of Brain: Brain box or Cranium, meninges and cerebrospinal fluid.
Protection of Spinal Cord: Vertebral Column, meninges and cerebrospinal fluid.

Question 15.
Mention one function for each of these hormones.
(a) Thyroxine
(b) Insulin
(c) Adrenaline
(d) Growth hormone
(e) Testosterone. (CCE 2010, 2013, 2015)
Answer:
(a) Thyroxine: Regulates metabolism of carbohydrates, fats and proteins, release of energy and body activity.
(b) Insulin: Regulates blood glucose by its absorption in liver, muscles (for formation of glycogen) and individual cells (for metabolic activity).
(c) Adrenaline: For meeting an emergency by increasing heart rate and supply of blood to various concerned organs.
(d) Growth Hormone (GH) or Somatotrophic Hormone: Regulates growth and development of the body through anabolic activity for growth of bones, muscles and visceral organs.
(e) Testosterone (Male Sex Hormone): Controls changes in body associated with puberty in males (beard, moustache, low pitch voice, increased growth of bones and muscles).

Question 16.
Name the various plant hormones. Also give their physiological effects on plant growth and development. (CCE 2016)
Answer:
Five types — auxin, gibberelin, cytokinin, ethylene and abscisic acid.
Auxin: Cell enlargement, root formation, apical dominance, inhibition of abscission, fruit growth.
Gibberellin: Growth in stem and leaves, higher fruit yield, overcoming dormancy.
Cytokinin: Essential for cell division, differentiation, prevention of senescence and overcoming apical dominance.
Ethylene: Promotes transverse growth, fruit ripening and overcoming dormancy of some parts.
Abscisic Acid (ABA): Induces dormancy, senescence and abscission, checking excessive activity of growth promoting hormones, closure of stomata under water stress.

Question 17.
What are reflex actions ? Give two examples. Explain a reflex arc.
Answer:
Definition: Reflex actions seem to have evolved quite early in the physiology of animals when complex neuron network for processing had not been evolved. Even after evolution of processing centres, reflex actions have continued to persist because of their more efficiency for quick responses.
Two Examples:

1. On being pricked or coming in contact with hot surface, hand is withdrawn even before pain is perceived (by brain),
2. Wider openin0 of pupil in dim light and its narrowing in strong light.
   

Question 18.
“Nervous and hormonal systems together perform the function of control and coordination in human being.” Justify the statement.
Answer:
Both nervous system and hormonal (or endocrine) system are involved in control, regulation and coordination of body parts. Nervous system is connected to receptors of all senses. Information obtained from sensory organs is passed rapidly to CNS for interpretation.
On the basis of interpretation, a message is sent to effector organ or organs (muscles, glands, etc.). The rate of information or impulse transfer is very high, some 100m/sec. Every action and activity is well coordinated as the information is sent to all the regions required for that action. The action can be voluntary (under the will) or involuntary. Passage of food in the alimentary canal is due to an involuntary movement of alimentary canal called peristalsis. Picking up food and placing it inside the mouth is a voluntary movement. Both these movements are highly coordinated by nervous system.
Nervous system is also connected with the functioning of endocrine or hormonal system. The endocrine system functions at the biochemical level while nervous system functions at the physical and physiological level. For their functioning endocrine glands pour their secretion into blood which transports them to all parts of the body. Target cells have receptors for picking up the hormones and working as per hormonal stimulus. There is a feedback system which determines the requirement of hormones and the activity of endocrine glands. Other stimuli are also involved for coordinated functioning. Presence of food in the stomach stimulates its wall to secrete hormone gastrin. Gastrin stimulates gastric glands to pour gastric juice over the food. As the partially digested food passes into duodenum, the latter forms hormone secretin which induces passage of bile and pancreatic juice into duodenum.
Joint working of both the systems is observed during an emergency. Both sympathetic nervous system and adrenal glands prepare the body for meeting the emergency. There is higher rate of heart beat, more blood supply to cardiac and skeletal muscles and higher rate of breathing for quicker oxygenation of blood.

Question 19.
How does chemical co-ordination take place in animals ?
Answer:
In animals, chemical coordination is achieved through the agency of hormones which function as chemical messengers or informational molecules. Hormones are secreted by ductless glands in response to specific conditions or nervous stimulation. Timing and amount of a hormone released are regulated by feed-back mechanism. After a meal, sugar level of blood rises. It is detected by pancreas. Pancreas responds by producing hormone insulin from (3-cells of islets of Langerhans. Insulin causes glucose to be absorbed by all cells as well as get stored in liver and muscles in the form of glycogen. As the level of glucose falls in blood, insulin secretion is reduced.

Question 20.
Why the flow of signals in a synapse is from axonal end of one neuron to dendrite end of another neuron but not the reverse ?
Answer:
As the electrical impulse reaches the axon terminal in the region of axon-dendrite synapse, it stimulates the exocytosis of vesicles containing neurotransmitter (e.g. acetylcholine). Neurotransmitter attaches to the chemoreceptor sites of the membrane covering the dendrite end of synapse. It creates a new impulse that travels through cell body and axon of the second neuron. At synapse, the axon end does not contain any chemoreceptor sites so that reverse flow of electrochemical impulses is not possible.

Extra Questions – Control and Coordination – CBSE Class 10 Science

Question-1
What is a neuron?
Solution:
A neuron is a nerve cell that is the basic building block of the nervous system. Neurons are similar to other cells in the human body in a number of ways, but there is one key difference between neurons and other cells. Neurons are specialized to transmit information throughout the body.
These highly specialized nerve cells are responsible for communicating information in both chemical and electrical forms. There are also several different types of neurons responsible for different tasks in the human body.
Question-2
Name any two types of tropism.
Solution:
The two types of tropism are phototropism and geotropism.

Question-3
What is a phytohormone? Name any two phytohormones.
Solution:
Phytohormones are chemical substances, which are produced naturally in plants and are capable of translocation and regulating one or more physiological reactions when present in appropriate concentrations. The two phytohormones are auxins and gibberellins.
Question-4
Mention the receptors for light and sound in animals.
Solution:
Photoreceptor is the receptor for light and phonoreceptor is the receptor for sound in animals.
Question-5
How does control and coordination takes place in plants?
Solution:
Plants have a unique mechanism of controlling and coordinating its various physiological and biological processes. Plants respond to light, touch, gravitational force and other stimuli. Growth and movements in plants are regulated by both external and internal factors. The functions of control and coordination in plants are performed by chemical substances known as plant hormones or phytohormones.

Question-6
Mention the names of various phytohormones.
Solution:
The various phytohormones are auxins, gibberellins, cytokines, abscises acid and ethylene.

Question-7
Discuss phototropism.
Solution:
The movement of plants toward light is called phototropism.
Question-8
Differentiate between tropic and nastic movements.
Solution:
Tropic movement:
The movement of a plant in the direction of stimulus.
Nastic movement:
The movements, which are neither towards nor away from the stimulus.
Question-9
Draw the diagram of a neuron.
Solution:

Question-10
Draw a neat diagram of the nervous system in an insect.
Solution:

Question-11
Describe the central nervous system in human beings.
Solution:
The central nervous system in human beings is highly developed. It consists of
(i) brain and (ii) spinal cord. Brain is the highest coordinating centre in the body. It is protected by a bony box in the skull called the cranium. Brain is covered by three membranes, called meninges. The space between the membranes is filled by cerebrospinal fluid that protects the brain from mechanical shocks.
The brain is broadly divided into three regions
(i) Fore brain (ii) Mid brain and (iii) Hind brain.
Each region of the brain consists of various centers. The fore brain includes cerebrum and olfactory lobes.The cerebrum is the most complex and specialized part of the brain. It consists of two cerebral hemispheres.The cerebrum has sensory areas where information is received from sense organs. Similarly, there is the motor area from where impulses are sent to the muscle or effectors organs. In the cerebrum, specific regions for each kind of stimulus and its response are located. Pairs of cranial nerves arise from the brain. The hind brain consists of three centers, cerebellum, pons and medulla oblongata. Medulla oblongata is the regulating centre for swallowing, coughing, sneezing and vomiting. The pons takes part in regulation of respiration. Coordination and the adjustment of movement and posture are under the control of cerebellum.
Spinal cord is a part of the central nervous system, which lies in the vertebral canal. It is a downward continuation of the medulla oblongata. In the spinal cord, the arrangement of white and grey matter is reverse of that of the brain. The grey matter containing cytons is the inner region and white matter containing myelinated axons is the outer. In the centre of the spinal cord runs a small central canal. This central canal, which runs the entire length of the spinal cord, is continuous with the ventricles of the brain. The spinal cord in transverse section has H-shaped structure because it has fissures on the ventral and the dorsal sides. The dorsal fissure almost reaches the gray matter while the anterior median fissure falls short of it. Spinal cord gives off 31 pairs of nerves.
Question-12
Write the functions of any one part of the hind – brain.
Solution:
Cerebellum is the part of the hind – brain that controls and coordinates the movements of our body and helps in adjusting the posture. It functions even when the person is asleep.
Question-13
What is the autonomic nervous system?
Solution:
The autonomic nervous system controls the involuntary action of the body. It mainly controls and integrates the functions of internal organs like heart, blood vessels, glands, smooth muscles and uterus in the body. The autonomic nervous system is subdivided into (i) sympathetic and (ii) parasympathetic system. The organs receive nerves from both sympathetic and parasympathetic nerve fibers. They have antagonistic effects on the organs if one is stimulatory, the other is inhibitory.
Question-14
Define reflex action with suitable examples.
Solution:
When we suddenly withdraw our hands on pricking a pin, it is a reflex action. This type of sudden response to a stimulus is involuntary. A reflex action is defined as an unconscious and involuntary response of effectors to a stimulus. In reflex actions, a message from the receptors is relayed by sensory nerves to the spinal cord, which sends information for response via motor nerves to effectors. The pathway is called reflex arc. The simplest type of reflex action is knee-jerk reflex. In this case, while sitting with freely hanging legs, a strike below the knee cap kicks the leg forward. Other reflex actions are coughing, sneezing, yawning and blinking of eyes.
Question-15
Name the hormones secreted by thyroid, parathyroid and pancreas.
Solution:
(i) Thyroid secretes thyroxin,
(ii) Parathyroid secretes calcitonin and
(iii) Pancreas secrete insulin and glucagons.
Question-16
List the functions of testosterone and estrogen.
Solution:
The functions of testosterone are the regulation of male accessory sex organs and secondary sexual characters like moustache, beard and voice.
The functions of estrogen are the regulation of female accessory sex organs and secondary sexual characters like mammary glands, hair pattern and voice, and the maintenance of pregnancy.
Question-17
Write name of three hormones secreted by the pituitary gland.
Solution:
The three hormones secreted from pituitary gland are
(i) growth hormone, (ii) adrenocorticotrophic hormone and (iii) follicle stimulating hormone (FSH).
Question-18
Nervous and hormonal system together perform the function of control and coordination in human beings. Justify the statement.
Solution:
In humans, the nervous system is the most important, rather essential, system for regulation, control and coordination of body functions. It makes possible a range of adaptive responses to changes in the environment in the interests of the individuals. This system helps the individual to respond in a coordinated manner to environmental changes, to control various movements and to prolong the life by protecting the body against harmful stimuli. Coordination in humans is brought about by the secretions of endocrine glands. Endocrine glands are the ductless glands, which secrete the chemical substances called hormones directly into the blood. Any chemical substance, which is formed in the tissues of endocrine glands and are carried by the blood to other parts of the body for its specific actions is termed as a hormone. An organ, which responds to such a hormone, is known as the target organ. Hence, hormones and nervous system together perform the function of control and coordination in the human beings.
Question-19
What is hydrotropism?
Solution:
Hydrotropism is a type of tropism, where the plant shows movement in response to water.
Question-20
What is coordination?
Solution:
The organ system cannot work independently. They are linked in one way or the other. Working together of all these systems is called coordination.
Question-21
Why is the response of a plant to a stimulus not observed immediately?
Solution:
The response of a plant to a stimulus not observed immediately because the plant shows its response very slowly.
Question-22
What are hormones?
Solution:
Any chemical substance which is formed in the tissues of endocrine glands and are carried by the blood to other parts of the body for its specific actions is termed is hormone.
Question-23
What are phytohormones?
Solution:
A phytohormones can be defined as chemical substances, which are produced naturally in plants and are capable of translocation and regulating one or more physiological processes when present in low concentration.
Question-24
What are meanings? What are their functions? Name the fluid, which is filled in between meanings.
Solution:
The brain is surrounded by three membranes called meanings, which help to protect the brain. The space between the meanings is filled with cerebra spinal fluid, which protects the brain from mechanical shocks.
Question-25
How does control and coordination occur in single-celled animals?
Solution:
The cytoplasm of the single-celled animal controls and coordinates the activities of the organism.
Question-26
Name any two phytohormones, which are growth promoters.
Solution:
The two phytohormones, which are growth promoters are Auxins and Gibberellins.
Question-27
Name any growth inhibiting phytohormone.
Solution:
Abscises acid is a growth inhibiting phytohormone.
Question-28
What makes a stem bend towards sunlight?
Solution:
The chemical substance called plant hormone or phytohormone makes a stem bend towards sunlight.

CBSE Class 10 Science Notes Chapter 7 Control and Coordination

Control and Co-ordination in Animals: Nervous system and endocrine system.
In animals, the nervous system and hormonal system are responsible for control and co¬ordination.

Receptors: Receptors are the specialized tips of the nerve fibres that collect the information to be conducted by the nerves.
Receptors are in the sense organs of the animals.
These are classified as follows :

• Phono-receptors: These are present in inner ear.
  Functions: The main functions are hearing and balance of the body.
• Photo-receptors: These are present in the eye.
  Function: These are responsible for visual stimulus.
• Thermo-receptors: These are present in skin.
  Functions: These receptors are responsible for pain, touch and heat stimuli.
  These receptors are also known as thermoreceptors.
• Olfactory-receptors: These are present in nose.
  Functions: These receptors receive smell.
• Gustatory-receptors: These are present in the tongue.
  Functions: These helps in taste detection.

Nervous System: The nervous system is composed of specialized tissues, called nervous tissue. The nerve cell or neuron is the functional unit of the nervous system. It is the nervous system which is mainly responsible for control and coordination in complex animals.

Functions of the nervous system

• Nervous system receives information from the environment.
• To receive the information from the various body.
• To act according to through muscles and glands.

A neuron is the structural and functional unit of the nervous system.

Neuron: Neuron is a highly specialized cell which is responsible for the transmission of nerve impulses. The neuron consists of the following parts
(i) Cyton or cell body: The cell body or cyton is somewhat star-shaped, with many hair like structures protruding out of the margin. These hair-like structures are called dendrites. Dendrites receive the nerve impulses.
(ii) Axon: This is the tail of the neuron. It ends in several hair-like structures, called axon terminals. The axon terminals relay nerve impulses.
(iii) Myelin sheath: There is an insulator cover around the axon. This is called myelin sheath. The myelin sheath insulates the axon against nerve impulse from the surroundings.

Types of neuron

• Sensory neuron: These neurons receive signals from a sense organ.
• Motor neuron: These neurons send signals to a muscle or a gland.
• Association or relay neuron: These neurons relay the signals between sensory neuron and motor neuron.

Synapse: The point contact between the terminal branches of axon of one neuron with the dendrite of another neuron is called synapse.

Neuromuscular Junction (NMJ): NMJ is the point where a muscle fibre comes in contact with a motor neuron carrying nerve impulse from the control nervous system.

Transmission of nerve impulse: Nerve impulses travel in the following manner from one neutron to the next :
Dendrites → cell body → axon → nerve endings at the tip of axon → synapse → dendrite of next neuron.
Chemical released from axon tip of one neuron, cross the synapse or neuromuscular junction to reach the next cell.

Human Nervous System: The nervous system in humans can be divided into three main parts
1. Central Nervous System: The central nervous system is composed of the brain and the spinal cord. The brain controls all the functions in the human body. The spinal cord works as the relay channel for signals between the brain and the peripheral nervous system.

2. Peripheral Nervous System: The peripheral nervous system is composed of the cranial nerves and spinal nerves. There are 12 pairs of cranial nerves. The cranial nerves come our of the brain and go to the organs in the head region. There are 31 pairs of spinal nerves. The spinal nerves come out of the spinal cord and go to the organs which are below the head region.

3. Autonomous Nervous System: The autonomous nervous system is composed of a chain of nerve ganglion which runs along the spinal cord. It controls all the involuntary actions in the human body. The autonomous nervous system can be divided into two parts :

• Sympathetic nervous system.
• Parasympathetic nervous system.

Sympathetic Nervous System: This part of the autonomous nervous system heightens the activity of an organ as per the need. For example, during running, there is an increased demand for oxygen by the body. This is fulfilled by an increased breathing rate and increased heart rate. The sympathetic nervous system works to increase the breathing rate the heart rate, in this case.

Parasympathetic Nervous System: This part of the autonomous nervous system slows the down the activity of an organ and thus has a calming effect. During sleep, the breathing rate slows down and so does the heart rate. This is facilitated by the parasympathetic nervous system. It can be said that the parasympathetic nervous system helps in the conservation of energy.

Human Brain: Human brain is a highly complex organ, which is mainly composed of nervous tissue. The tissues are highly folded to accommodate a large surface area in less space. The brain is covered by a three-layered system of membranes, called meninges. Cerebrospinal fluid is filled between the meninges. The CSF providers cushion the brain against mechanical shocks. Furthermore, protection. The human brain can be divided into three regions, viz. forebrain, midbrain and hindbrain.

Parts of Human Brain :

• Fore-brain: It is composed of the cerebrum.
• Mid-brain: It is composed of the hypothalamus.
• Hind-brain: It is composed of the cerebellum, pons, medulla, oblongata.

Some main structures of the human brain are explained below :
Cerebrum: The cerebrum is the largest part in the human brains. It is divided into two hemispheres called cerebral hemispheres.

Functions of cerebrum

• The cerebrum controls voluntary motor actions.
• It is the site of sensory perceptions, like tactile and auditory perceptions.
• It is the seat of learning and memory.

Hypothalamus: The hypothalamus lies at the base of the cerebrum. It controls sleep and wake cycle (circadian rhythm) of the body. It also controls the urges for eating and drinking.

Cerebellum: Cerebellum lies below the cerebrum and at the back of the whole structure. It coordinates the motor functions. When you are riding your bicycle, the perfect coordination between your pedalling and steering control is achieved by the cerebellum.

• It controls posture and balance.
• It controls the precision of voluntary action.

Medulla: Medulla forms the brain stem, along with the pons. It lies at the base of the brain and continues into the spinal cord. The medulla controls various involuntary functions, like hear beat respiration, etc.
It controls involuntary actions.
Example: Blood pressure, salivation, vomiting.

Pons: It relays impulses between the lower cerebellum and spinal cord, and higher parts of the brain like the cerebrum and midbrain, also regulates respiration.

Spinal cord: Spinal cord controls the reflex actions and conducts massages between different parts of the body and brain.

Reflex Action: Reflex action is a special case of involuntary movement involuntary organs. When a voluntary organ is in the vicinity of sudden danger, it is immediately pulled away from the danger to save itself. For example, when your hand touches a very hot electric iron, you move away your hand in a jerk. All of this happens in flash and your hand is saved from the imminent injury. This is an example of reflex action.

Reflex Arc: The path through which nerves signals, involved in a reflex action, travel is called the reflex arc. The following flow chart shows the flow of signal in a reflex arc.
Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector (muscle)
The receptor is the organ which comes in the danger zone. The sensory neurons pick signals from the receptor and send them to the relay neuron. The relay neuron is present in the spinal cord. The spinal cord sends signals to the effector via the motor neuron. The effector comes in action, moves the receptor away from the danger.

The reflex arc passes at the level of the spinal cord and the signals involved in reflex action do not travel up to the brain. This is important because sending signals to the brain would involve more time.
Although every action is ultimately controlled by the brain, the reflex action is mainly controlled at the level of spinal cord.

Protection of brain and spinal cord
Brain is protected by a fluid filled balloon which acts as shocks absorber and enclosed in cranium (Brain box)
Spinal chord is enclosed in vertebral column.

Muscular Movements and Nervous Control: Muscle tissues have special filaments, called actin and myosin. When a muscle receives a nerve signal, a series of events is triggered in the muscle. Calcium ions enter the muscle cells. It result in actin and myosin filaments sliding towards each other and that is how a muscle contracts. Contraction in a muscle brings movement in the related organ.

Endocrine System: The endocrine system is composed of several endocrine glands. A ductless gland is called endocrine gland. Endocrine gland secretes its product directly into the bloodstream. Hormones are produced in the endocrine glands. Hormone is mainly composed of protein. Hormones assist the nervous system in control and co-ordination. Nervous do not react to every nook and corner of the body and hence hormones are needed to affect control and coordination in those parts. Moreover, unlike nervous control, hormonal control is somewhat slower.

Hormones: These are the chemical messengers secreted in very small amounts by specialised tissues called ductless glands. They act on target tissues/organs usually away from their source. Endocrine System helps in control and coordination through chemical compounds called hormones.

Endocrine Gland: A ductless gland that secretes hormones directly into the bloodstream.

Endocrine  Gland	Location	Hormones Produced	Functions
Pituitary gland (also known as the master gland)	At the base of the brain	Growth hormone (GH). Thyroid stimulating hormone (TSH). Follicle stimulating hormone (FSH)	GH stimulates growth. TSH stimulates the functioning of the thyroid gland. FSH stimulates the follicles during ovulation.
Thyroid Gland	Neck	Thyroxine	Controls general metabolism and growth in the body.
Adrenal gland	Above kidneys	Adrenalin	Prepares the body for emergency situations and hence is also called ‘Fight and flight’ hormone.
Pancreas	Near stomach	Insulin	Controls blood sugar level
Testis (male)	In Scrotum	Testosterone	Sperm production, development of secondary sexual characters during puberty.
Ovary (female)	Near uterus	Oestrogen	Egg production, development of secondary sexual characters during puberty.

Iodised salt is necessary because: Iodine mineral is essential part of thyronine hormone so it is important that we must consume iodised salt as in turn it is essential for thyroid gland as it controls carbohydrate, proteins and fat metabolism for best balance of growth deficiency of iodine might cause disease called goitre.

Diabetes: Cause : It is due to deficiency of insulin hormone secreted by pancreas that is responsible to lower/control the blood sugar levels.

Treatment : Patients have to internally administer injections of insulin hormone which helps in regulating blood-sugar level.

In case of flight or fight reaction to an emergency situation, Adrenal glands → release adrenaline into blood → which acts on heart and other tissues → causes faster heart beat → more oxygen to muscles → reduced blood supply to digestive system and skin → diversion of blood to skeletal muscles → increase in breathing rate.

Feedback mechanism: A type of self-regulating mechanism in which the level of one substance in body influences the level of another.

Control and Co-ordination in Plants: Movements in plants and plant harmones.
Co-ordination in Plants: Unlike animals, plants do not have a nervous system. Plants use chemical means for control and co-ordination. Many plant hormones are responsible for various kinds of movements in plants. Movements in plants can be divided into two main types :

1. Tropic movement
2. Nastic movement

1. Tropic Movement: The movements which are in a particular direction in relation to the stimulus are called tropic movements. Tropic movements happen as a result of growth of a plant part in a particular direction. There are four types of tropic movements.
(i) Geotropic movement: The growth in a plant part in response to the gravity is called geotropic movement. Roots usually show positive geotropic movement, i.e. they grow in the direction of the gravity. Stems usually show negative geotropic movement.

(ii) Phototropic Movement: The growth in a plant part in response to light is called phototropic movement. Stems usually show positive phototropic movement, while roots usually show negative phototropic movement. If a plant is kept in a container in which no sunlight reaches and a hole in the container allows some sunlight; the stem finally grows in the direction of the sunlight. This happens because of a higher rate of cell division in the part of stem which is away from the sunlight. As a result, the stem bends towards the light. The heightened rate of cell division is attained by increased secretion of the plant hormone auxin in the which is away from sunlight.

(iii) Hydrotropic Movement: When roots grow in the soil, they usually grow towards the nearest source of water. This shows a positive hydrotropic movement.

(iv) Thigmotropism Movement: The growth in a plant part in response to touch is called thigmotropism movement. Such movements are seen in tendrils of climbers. The tendril grows in a way so as it can coil around a support. The differential rate of cell division in different parts of the tendril happens due to action of auxin.

2. Nastic Movement: The movement which do not depend on the direction from the stimulus acts are called nastic movement. For example, when someone touches the leaves of mimosa, the leaves droop. The drooping is independent of the direction from which the leaves are touched. Such movements usually happen because of changing water balance in the cells. When leaves of mimosa are touched, the cells in the leaves lose- water and become flaccid, resulting in drooping of leaves.

Plant hormones: Plant hormones are chemical which help to co-ordinate growth, development and responses to the environment.
Type of plant hormones: Main plant hormones are

• Auxin: (Synthesized at shoot tip).
  Function: Helps in growth.
  Phototropism: more growth of cells towards the light.
• Gibberellin: Helps in the growth of the stem.
• Cytokinins: Promotes cell division.
• Abscisic acid: Inhibits growth, cause wilting of leaves. (Stress hormone)

Control and Coordination in Plants

• Stimuli: The change in the environment to which an organism responds.
• Co-ordination: Working together of various organs of an organism in a systematic manner to produce a proper response.
• Phyto-hormones: These are plant hormones.
• Auxin: It is a plant hormone which promotes cell enlargement and growth in plants.
• Gibberellins: A plant hormone which promotes cell differentiation and breaking dormancy of seeds and buds.
• Cytokinin: A plant hormone which promotes cell division and the opening of stomata.
• Abscisic Acid: It helps in inhibiting the growth of the plant and promotes wilting and falling of leaves and food.
• Tropism: A growth movement of a plant which determines direction with the stimulus.
• Nastism: A growth movement of a plant which does not determine direction with a stimulus.
• Phototropism: Movement of plants towards a light.
• Geotropism: Movement of plants towards the gravity of earth.
• Chemotropism: Movement of plants towards chemicals.
• Hydrotropism: Movement of plants towards the water.
• Thigmotropism: Movement of plants towards a response to the touch of an object.

Control and Coordination in Animals

• Stimuli: The change in the environment to which the organism responds.
• Co-ordination: Working together of various organs of an organism in a systematic manner to produce a proper response.
• Neuron: Functional unit of the nervous system.
• Synapse: A microscopic gap between a pair of adjacent neurons.
• Receptor: A cell in a sense organ which is sensitive to stimuli.
• Motor nerves: It carries the message from the brain to body parts for action.
• Sensory nerves: It carries the message from body to brain.
• Olfactory receptor: It detects smell by the nose.
• Gustatory receptor: It detects taste by a tongue.
• Thermoreceptor: It detects heat and cold by a skin.
• Photoreceptor: It detects light by eye.
• Reflex action: Sudden movement or response to the stimulus which occurs in a very short duration of time and does not involve any will or thinking of the brain.
• Brain: An organ present in the skull which controls and regulates the activity of the whole body and is known as president of the body.
• Cerebrum: Main thinking part of brain present in the forebrain area which controls all voluntary actions.
• Cerebellum: It is present in the hindbrain area and helps in maintaining posture and balance of the body.
• Medulla: It is present in the hindbrain area and helps in controlling voluntary actions of the brain.
• Spinal cord: It is a cylindrical structure of nerve fibres enclosed in the vertebral column which helps in the conduction of nerve impulses to and from the brain.

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