Lakhmir Singh & Manjit Kaur: Control & Coordination, Solutions- 3 | Science Class 10 PDF Download

Page No - 116

Question 32:
(a) What are the various sense organs in our body ?
(b) What is meant by receptors and effectors ? Give two examples of each.
Solution :
(a) There are 5 sense organs: Eyes, ears, nose, tongue and skin.
(b) A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a particular type of stimulus (or a particular type of change in the environment).
Example: Photoreceptors and Phonoreceptors.An effecter is the part of the body which can respond to the stimulus according to the instructions sent from the nervous system (spinal cord and brain).
Example: Muscles and glands.

Question 33:
(a) What is spinal cord ? What is its main function ?
(b) Give the functions of medulla.
Solution :
(a) Spinal cord is a cylindrical structure which begins in continuation with medulla and extends downwards. Its function is the conduction of nerve impulses to and from the brain and it is concerned with spinal reflex actions.
(b) The medulla controls various involuntary actions such as heart beat, breathing, blood pressure and peristaltic movements of the elementary canal.
It is also the controlling centre for reflexes such a swallowing, coughing, sneezing, secretion of saliva and vomiting.

Question 34:
(a) Name the three types of nerves which constitute the peripheral nervous system.
(b) What is the difference between a reflex action and walking ?
(c) How do we detect the smell of an incense stick (agarbatti) ?
Solution :
(a) The three types of nerves which make up the peripheral nervous system are: spinal nerves, cranial nerves and visceral nerves.
(b)

(c) When the agarbatti burns, it produces vapours having a characteristic pleasant smell which is detected by the olfactory receptors present inside our nose. The action of smell of agarbatti or receptors sets off chemical reactions which generate electrical impulses. The sensory neurons carry these electric al impulses to the sensory area of fore brain called cerebrum. This makes us detect the smell of burning agarbatti.

Question 35:
(a) What substances are made by endocrine glands ?
(b) What is the function of receptors and effectors in our body ?
Solution :
(a) Hormones are made by endocrine glands.
(b) Receptors are the special cells present in our sense organs which detect all the information from our environment and feed it to the nervous system. An effector responds to electrical impulses sent from the nervous system through motor nerves.

Question 36:
(a) Name the hormones secreted by the following endocrine glands :
(i) Thyroid gland (ii) Parathyroid glands (iii) Pancreas (iv) Adrenal glands
(b) Write the functions of testosterone and oestrogen hormones.
Solution :
(a)
(i) Thyroxine
(ii) Parathromone
(iii) Insulin
(iv) Adrenaline.
(b) The function of testosterone hormone is to control the development of male sex organs and male features such as deeper voice, moustache, body hairs etc. The function of oestrogen is to control the development of female sex organs and female features such as feminine voice, soft skin and mammary glands.

Question 37:
(a) Write the names of the regions in hindbrain. Give one function of each region.
(b) Name the functions of cerebrum.
Solution :
(a) Hindbrain has 3 regions:
(i) Pons: It takes part in regulating respiration.
(ii) Cerebellum: It helps in maintaining posture and balance of the body. It enables us to make precise and accurate movements.
(iii) Medulla: The medulla controls various involuntary actions such as heart beat, breathing, blood pressure and peristaltic movements of the elementary canal. It is also the controlling centre for reflexes such a swallowing, coughing, sneezing, secretion of saliva and vomiting.
(b) Function of cerebrum: It is the main thinking part of the brain. It is the site of our faculties such as learning, reasoning, intelligence, personality and memory. All our thoughts, sensation, actions and movements are controlled by cerebrum.

Question 38:
(a) The human brain can be broadly divided into three regions. Name these three regions.
(b) What is cranium ? What is its function ?
Solution :
(a) The 3 regions of human brain are
(i) Forebrain
(ii) Midbrain and
(iii) Hindbrain.
(b) Cranium is a bony box in the skull in which the brain is present. Its function is to protect the brain.

Question 39:
(a) How does chemical coordination take place in human beings ?
(b) Why is the use of iodised salt advisable ?
Solution :
(a) The chemical coordination in animals takes place through the actions of chemicals called hormones which are release directly into the blood and are carried by the blood circulatory system to other parts of the body. Hormones travel all over the body but affect only particular organs at particular places which are called target organs. The organs control and coordinate several functions of animal body such as growth, development, metabolism, behavior and secondary sexual characteristics, etc.
(b) Iodine is necessary for the thyroid gland to make thyroxine hormone which regulates the metabolism of carbohydrates, fats and proteins so as to produce the best balance for the growth. Iodised salt is advisable as it contains appropriate amounts of iodine compounds needed by the thyroid gland to make sufficient thyroxine hormone for the body and hence goitre disease can be prevented.

Question 40:
What is the function of insulin hormone ? What type of patients are given insulin injections ?
Solution :
The function of insulin hormone is to lower the blood sugar level (or blood glucose level). People having severe diabetes are treated by giving injections of insulin.

Question 41:
Compare the nervous system and endocrine system (hormonal system) for control and coordination in humans.
Solution :
Nervous System
It is a system to coordinate the activities of bodies. It helps all other system of our body to work together. It receives information from the surroundings, processes it, interprets it and then responds accordingly.
Endocrine System
It is a group of endocrine glands which produces various hormones that helps in coordinating the activities of our body. The hormones produced by the endocrine glands act as messengers between the nervous system and the organs of our body.

Question 42:
State the functions of the following hormones :
(a) Thyroxine (b) Adrenaline (c) Growth hormone
Solution :
(a) Thyroxine ? The function of this hormone is to control the rate of metabolism of carbohydrates, fats and proteins in the body.
(b) Adrenaline ? Its function is to regulate heart rate, breathing rate, blood pressure and carbohydrate metabolism.
(c) Growth hormone ? It controls the growth of the human body.

Question 43:
Write the names of all the major endocrine glands present in the human body. Which of these glands also function as exocrine glands ?
Solution :
The endocrine gland present in the human body are:
(i) Pineal gland
(ii) Hypothalamus
(iii) Pituitary
(iv) Thyroid
(v) Parathyroid
(vi) Thymus
(vii) Pancreas
(viii) Adrenal glands
(ix) Testes (in males)
(x) Ovaries (in females). Pancreas, testes and ovaries function as exocrine glands.

Question 44:
Match the hormones given in column I with their functions given in column II :

Solution :
(i) d
(ii) c
(iii) e
(iv) a
(v) b

Question 45:
A person walks across a room in barefeet and puts his foot on a drawing pin lying on the floor. He lets out a cry. Explain what happens in his nervous system in bringing about this response.
Solution :
It is an example of reflex action. The stimulus here is drawing pin lying on the floor. The pain is sensed by the receptors in the skin which triggers and impulse in a sensory neuron and transmits the message to the spinal cord. The impulse is passed onto a relay neuron, which in turn, passes it to the motor neuron. The motor neuron passes the impulse to a muscle in the feet. The muscle then contracts and pulls our feet away from the drawing pin.

Question 46:
In what ways are puberty and adolescence result of the activity of some glands in the human body ?
Solution :
Puberty and adolescence are the results of sex glands in human beings. In males, testes make male sex hormones called testosterone which is associated with male puberty, which the boys attain an age of 13-14 years. In females the oestrogen hormone is responsible for all the changes associated with female puberty which the girl attains at an age of 10-12 years.

Question 47:
List three ways in which neurons are similar to other cells.
Solution :
Neurons and other cells have a cell membrane, cytoplasm and a nucleus.

Question 48:
Explain the difference between each of the following pairs of terms :
(a) receptor and effector (b) cerebrum and cerebellum
Solution :
(a)
Receptor
A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a particular type of stimulus (or a particular type of change in the environment).
Example: Photoreceptors and Phonoreceptors.
Effector
An effector is the part of the body which can respond to the stimulus according to the instructions sent from the nervous system (spinal cord and brain).
Example: Muscles and glands.
(b)
Cerebrum
(i) It is a part of forebrain.
(ii) It is the main thinking part of the brain. All our thoughts, sensation, actions and movements are controlled by cerebrum.
Cerebellum
(i) It is a part of hindbrain.
(ii) It helps in maintaining posture and balance of the body. It enables us to make precise and accurate movements.

Question 49:
What is the difference between a voluntary and an involuntary action ? Which kind of action is digestion ? Explain your choice.
Solution :

Digestion is an involuntary action as it does not involve the thinking process and is performed unknowingly by our digestive system.

Question 50:
What does CNS stand for ? Which part of CNS : (a) consists of two cerebral hemispheres, and (b) has spinal nerves attached to it ?
Solution :
(i) CNS – Central nervous system.
(ii)
(a) Cerebrum
(b) Spinal cord.

Question 51:
Which hormone :
(a) prepares the body for action ?
(b) controls the amount of glucose in blood ?
(c) gives boys a deep voice ?
(d) gives girls soft skin ?
Solution :
(a) Adrenaline.
(b) Insulin.
(c) Testosterone.
(d) Oestrogen.

Page No - 117

Question 52:
When you smell a favourite food your mouth begins to water (that is, you secrete saliva). Write down what the following are examples of :
(a) the smell of the food
(b) the cells in your nasal passages which perceive the smell
(c) the gland which is stimulated to secrete saliva.
Solution :
(a) Stimulus.
(b) Receptors (Olfactory).
(c) Effector (Salivary glands).

Question 53:
(a) Name the structural and functional unit of nervous system.
(b) Draw a flow chart to show the classification of nervous system into various parts.
(c) What is autonomic nervous system ? What is its function ?
(d) What is voluntary nervous system ? Explain the working of voluntary nervous system with an example.
Solution :
(a) Te structural and functional unit of nervous system is neuron.
(b) The classification of nervous system into various parts is given in the following chart:

(c) Autonomic nervous system means self governing nervous system. Its function is to control and regulate the functions of the internal organs of our body involuntarily.
(d) The voluntary nervous system is a system which helps us to take voluntary actions which are under the conscious control of the brain. Example: If a student is getting late for school and sees his watch. He starts walking fast. In this process, the eyes see the time and send the information to the brain through the sensory nerves. The brain analyses the information and sends the instructions to walk faster to the muscle of our legs through the motor nerves. The muscles of the legs act accordingly and make the student walk faster.

Question54:
(a) What is a reflex action ? Explain with the help of an example.
(b) Define reflex arc. Give the flow chart of a spinal reflex arc.
(c) How are involuntary actions and reflex actions different from each other ?
Solution :
(a) The rapid, automatic response to a stimulus which is not under the voluntary action of the brain is called reflex action.Example: Moving our hand away on touching a hot plate.

(b) The pathway taken by the nervous impulse in our reflex action is called the reflex arc.

A reflex arc (This is actually a spinal reflex arc)

(c)

Question 55:
(a) What is the function of our nervous system ?
(b) What are the main organs of the human nervous system ? Draw a labelled diagram to show the main organs of the human nervous system.
(c) How does the human nervous system work ? Explain.
Solution :
(a) (i) The function of the nervous system is to coordinate the activities of our body. (ii) It helps all other systems of our body to work together. (iii) It receives information from the surroundings, processes it, interprets it and then responds accordingly. (b) The main organs of the nervous system are; brain, spinal cord and nerves. 

The human Nervous System

(c) When the sense organ in our body is affected, it sends the message to the brain in the form of electrical impulses through the sensory neurons. The brain analyses this message and decides the action to be taken. The brain then sends out instructions to the muscles of the concerned body parts through motor nerves and the concerned body part acts accordingly.

Question 56:
(a) What is a neuron ? Draw a labelled diagram of a neuron.
(b) What is a synapse ? What happens at the synapse between two neurons ? How are the messages carried across a synapse ? Explain with the help of a labelled diagram.
Solution :
(a) The unit which makes up the nervous system is called a neuron.

A neuron ( or nerve cell)

(b) A microscopic gap between a pair of adjacent neurons over which nerve impulses pass when going from one neuron to the next is called a synapse. Synapse between two neurons acts as a one way valve which allows electrical impulses to pass in one direction only. This happens as follows: When an electrical impulse coming from the receptor reaches the end of the axon of sensory neuron, then the electrical impulse releases tiny amount of a chemical substance called neuro transmitter substance into the synapse between two adjacent neurons. This substance crosses the synapse and starts a similar electrical impulse in the dendrite of the next neuron. In this way, the electrical impulses passes from one neuron to the next across the synapse. 

Question 57:
(a) Name two systems which taken together perform the functions of control and coordination in human beings.
(b) What does the central nervous system in humans consist of ? What is the job of the central nervous system ?
(c) Give the various functions of brain.
Solution :
(a) Nervous system and endocrine system.
(b) The central nervous system consists of the brain and spinal cord. The work of the CNS is to direct incoming messages to the motor neurons that are connected to the part of the body which will respond to a stimulus. It is involved in complicated responses where both (brain and spinal cord) work. It enables a person to give a more appropriate and more intelligent response to various situations.
(c)
(i) The brain receives information carrying nerve impulses from all the sensory organs of the body.
(ii) It responds to the impulses brought in by sensory organs by sending its own instructions through motor nerves to the muscles and glands causing them to function accordingly.
(iii) It correlates the various stimuli from different sense organs and produces the most appropriate and intelligent response.
(iv) It coordinates the body activities so that the mechanisms and chemical reactions of the body work together efficiently.
(v) It stores information so that behavior can be modified according to the past experience.

Question 58:
(a) Write the names of five endocrine glands found in the human body. Name the hormones secreted by each gland.
(b) How do hormones reach the organs they control ?
(c) Name the gland which controls the secretion of hormones from the pituitary.
(d) How does our body respond when adrenaline is secreted in large amounts into the blood ?
(e) Name the disease which occurs in adults due to the deficiency of iodine in the diet. What is the main symptom of this disease ?
Solution :
(a)
(i) Pituitary – Growth.
(ii) Thyroid – Thyroxine.
(iii) Pancreas – Insulin.
(iv) Adrenal – Adrenaline.
(v) Testes – Testosterone.
(b) The endocrine glands do not have ducts to secrete their hormones. They release hormones directly into the blood of a person and reach the concerned body part through the blood and act on it.
(c) Hypothalamus.
(d) The adrenaline hormone prepares our body to function at maximum efficiency during emergency situations like danger, anger etc. This adrenaline hormone increases our heartbeat, breathing rate, blood flow into muscles and causes liver to put more stored glucose into our blood. All these actions produce a lot of energy in our body and help us to cope up the emergency situations. Thus, when adrenaline is secreted in large amounts it prepares our body for action. (e) Goitre – The neck of the person appears to be swollen due to the enlargement of thyroid gland located in the neck.