(a) What are the various sense organs in our body ?
(b) What is meant by receptors and effectors ? Give two examples of each.
(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.
(a) What is spinal cord ? What is its main function ?
(b) Give the functions of medulla.
(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.
(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) ?
(a) The three types of nerves which make up the peripheral nervous system are: spinal nerves, cranial nerves and visceral nerves.
It is a rapid, automatic response to a stimulus which is not under the voluntary control of the brain . It is a kind of involuntary action which involves the spinal cord . It is not based on our thinking.
It is a voluntary action which we undertake knowingly. the action of walking involves thinking by the brain . the central nervous system (brain, spinal cord) takes part in the action of walking.
(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.
(a) What substances are made by endocrine glands ?
(b) What is the function of receptors and effectors in our body ?
(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.
(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.
(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.
(a) Write the names of the regions in hindbrain. Give one function of each region.
(b) Name the functions of cerebrum.
(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.
(a) The human brain can be broadly divided into three regions. Name these three regions.
(b) What is cranium ? What is its function ?
(a) The 3 regions of human brain are
(ii) Midbrain and
(b) Cranium is a bony box in the skull in which the brain is present. Its function is to protect the brain.
(a) How does chemical coordination take place in human beings ?
(b) Why is the use of iodised salt advisable ?
(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.
What is the function of insulin hormone ? What type of patients are given insulin injections ?
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.
Compare the nervous system and endocrine system (hormonal system) for control and coordination in humans.
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.
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.
State the functions of the following hormones :
(a) Thyroxine (b) Adrenaline (c) Growth hormone
(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.