NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination
Q1) Components of Neuron:
a) Cell body: The cell body of a neuron is also called cyton which is broad, rounded, pyriform or stellate part of the neuron. It has abundant cytoplasm, called neuroplasm which contains Nissl’s granules and a relatively large, spherical nucleus and is mainly concerned with metabolic maintenance and growth. It also receives nerve impulses from dendrites and transmits them to axon.
b) Dendrites: These are several short, tapering, much branched protoplasmic processes stretching out from the cell body of a neuron. Here sensation (information) is acquired which then travels as an electric impulse
towards the cell body.
c) Axon: It is a single, very long, cylindrical nerve fibre of uniform diameter arising from the cell body. At its terminal end, axon is highly branched. Axon terminals are often knob-like and these may end in nerve fibres that form synapses with dendrites of other neurons. The axon conducts nerve impulses away from the cell body
Q2) Types of neuron:
a) Sensory (receptor): Transmits impulse from sensory cells to Central Nervous System.
b) Motor (effector): Transmits impulse from Central Nervous System to muscle cells
c) Relay or Connector: Serves as a link between sensory and motor neurons.
Q3) Reflex action and reflex arcs: The simplest form of response in the nervous system is a reflex action. This is a rapid, automatic response to a stimulus that is not under the voluntary control of the brain. It is described
as an involuntary action that aims to protect ourselves. A knee jerk, movement of the diaphragm (during respiration), coughing, yawning, blinking of eyes and sneezing are all reflex actions. Coughing is a reflex action that clears our windpipe. The pupils of our eyes get smaller in bright light. This protects the retina of our eyes from damage due to too much light.
The pathway taken by nerve impulses in a reflex action is called the reflex arc. Reflex arcs allow rapid response
Q4) Why is a system of control and coordination essential in living organisms?
Ans: 1)Increase the chances of survival by responding to stimuli.
2) Different body parts function as a single unit.
3) To maintain homeostasis.
Q5) What is neuron?
Ans: Neuron is a nerve cell that is the functional and structural unit of the nervous system and has the capability to get excited by electrical or chemical impulses.
Q6) Define nerve impulse. Which structure in a neuron helps to conduct a nerve impulse:
i) towards the cell body?
ii) away from the cell body?
Ans: The information passing through the neurons is in the form of chemical and electrical signals. It is called nerve impulse.
i) Dendrites conduct the nerve impulse towards the cell body.
ii) Axon conducts the nerve impulse away from the cell body.
Q7) Distinguish between receptor and effector organ.
|Receptors are the organs responsible for receiving external stimuli and transmitting them to the Central Nervous System.||Effectors are the organs that carry out the central nervous system’s instructions in response to external stimuli.|
|All receptors are essentially supplied by sensory nerves that can carry the stimulus to the CNS.||Effectors are primarily supplied by motor nerves, which are capable of carrying instructions from the CNS.|
Q8) Which parts of the body form the central nervous system?
Ans: The central nervous system consists of the brain and the spinal cord.
Q9) What are the functions of brain?
Ans: a) It receives impulse from all the parts of the body, so it controls all the activities of body.
b) It responds to the signals by sending off instructions through the motor neurons to the muscles and glands for appropriate response.
c) It correlates the various stimuli from different sense organs and coordinates the body activities efficiently.
d) It stores information in itself as consciousness or knowledge and modifies behavior according to past experience.
Q10) What is spinal cord? Write its functions.
Ans: The spinal cord is a part of the central nervous system. It is a long pipe-like structure arising from the medulla oblongata, part of the brain consisting of a collection of nerve fibres, running through the vertebral column of the backbone.
a) It acts as the centre of reflex actions.
b) It is responsible for the conduction of nerve impulses to and from the brain.
c) It facilitates flexible movements
Q11) What is a plant hormone? Name four plant hormones. State one function of each.
Ans: The chemicals that perform the function of control and coordination in plants are called plant hormones.
The four plant hormones and their functions are as follows:
a) Auxin: It promotes cell enlargement and cell differentiation in plants.
b) Gibberellins: It breaks the dormancy in seeds and buds.
c) Cytokinins: These promote cell division in plants.
d) Abscisic acid: It promotes the closing of stomata.
Q12) What are animal hormones? List four characteristics of hormones.
Ans: Animal hormones are chemicals that are secreted by the endocrine glands. It is carried by the blood to the respective organs to regulate their physiological processes.
a) Hormones are secreted by the endocrine glands in small amounts.
b) The hormones are secreted directly into the blood and it is transported throughout the body.
c) They are chemical messengers that regulate the behaviour of the target cells.
d) The specific hormones act only on the target organs.
Q13) What are endocrine glands?
Ans: Endocrine glands are ductless glands that pour their secretions into the blood. The pituitary gland, thyroid gland, adrenal gland, etc., are examples of endocrine glands.
Functions of endocrine glands
a) Hormones are released into the bloodstream by endocrine glands. This allows hormones to flow to cells throughout the body.
b) Endocrine hormones play a role in mood regulation, growth and development, organ function, metabolism, and reproduction.
c) The amount of each hormone released is controlled by the endocrine system.
Q14) Which endocrine gland is called master gland?
Ans: The pituitary gland is called the master gland because it controls the secretions of other endocrine glands.
Question: What is the difference between a reflex action and 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: 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: Which part of the brain maintains posture and equilibrium of the body?
Answer: Posture and equilibrium of the body are controlled by cerebellum.
Question: 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: 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.
How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light ?
|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.
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.
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.
Question 1: How does chemical coordination take place in animals ?
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 ?
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.
How does our body respond when adrenaline is secreted into the blood ?
Answer: The heartbeat 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.
Why are some patients of diabetes treated by giving injections of insulin ?
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.
Which of the following is a plant hormone?
The gap between two neurons is called a
The brain is responsible for
(b) regulating the heart beat
(c) balancing the body
(d) all of the above
(b) All of the above
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]
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.
Draw the structure of a neuron and explain its function. [AICBSE 2017]
Nerve cell or neuron is the functional unit of nervous system. A nerve cell has three parts-
(i) cell body
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.
How does phototropism occur in plants ?
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.
Which signals will get disrupted in case of a spinal cord injury ?
(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.
How does chemical coordination occur in plants ?
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.
What is the need for a system of control and coordination in an organism ?
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.
How are involuntary actions and reflex actions different from each other ?
|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 that does not require any processing by brain.|
|2. Involuntary actions are controlled by mid and hind brain.||2. Reflex actions are controlled by spinal cord.|
Question 11: Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
|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: What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
|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.|
Question 1. What type of plant movement is seen in the diagram of coiling of tendril?
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.
Dorsal view of thyroid and parathyroid.
A – Thyroid,
What are the hormones involved in providing milk to the suckling infant ?
1. Prolactin (Maternity Hormone). Production of milk.
2. Oxytocin Ejection of milk.
How does pancreas control glucose level of blood ?
Pancreas produces two hormones
- Insulin from P-cells of islet of Langerhans and
- 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.
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 ?
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.
What is dormin ?
Dormin is the other name of plant hormone abscisic acid. The hormne induces dormancy in buds and seeds. So it has been called dormin.
- Name the parts labelled A and B in the neuron drawn above.
- Which part acquires the information in the neuron ?
- Through which part does the information travel ?
- In what form does this information travel ?
- 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.)
- A-Dendrite, B-Axon
- Dandrite to cell body or cyton to axon.
- Electrical impulse
- 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.
Function of Thyroxine. It controls
- Basal metabolic rate
- Metabalism of carbohydrates, fats and proteins
- Consumption of energy in physical activity and body temperature
- Development and differentiation.
(c) Iodised Salt: Salt is iodised to provide iodine to thyroid for synthesis of thyroxine which is iodine containing hormone.
How do tendrils reach the support when they do not have any sensory structures.
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.
Name the nervous system which controls the functioning of internal organs.
Autonomous or visceral nervous system.
Which system is working when you start sweating during exercise ? What is its function ?
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.
You can become moody by simply switching on night bulb daily. How can this happen ?
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.
What is the function of receptors in our body?
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.
What is the need for a system of control and coordination in an organism?
Coordination 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.
How are involuntary actions and reflex actions different from each other?
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.
What is the correct direction of flow of electrical impulses ? [NCERT Exemplar]
(c) Direction of flow of electrical impulse.
Impulse → Dendrite → Cell body → Axon → Release of chemicals that cross synapse → Dendrite of next neuron.
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?
(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.
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:
(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).
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?
(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.
Which of the following endocrine glands is unpaired? [NCERT Exemplar]
(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.