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1. Define irritability.

Ans: A basic tendency of showing responses to changes in the environment is called irritability.

2. What are stimuli and response?

Ans: The changes in environment are called stimuli. And the reaction of organisms to a stimulus is called response.

3. What is control and coordination system?

Ans: Co-ordination among various parts in the body which is in turn controlled by another system this is called control and co-ordination system.

4. What is tropism?

Ans: The movement of plants in response to various stimuli is called tropism.

Some types of tropisms are;

Phototropism : response towards light.

Geotropism : response towards gravity.

Hydrotropism : response towards water.

Thigmotropism : response towards touch.

Thermotropism : response towards temperature or heat.

Chemotropism : response towards chemicals.

5. What are plant hormones (phytohormones)?

Ans: Phytohormones are organic compounds that are produced in one tissue and translocated to another where they produce their specific effect, and regulate plants growth and development.

6. Name the two categories of growth regulators. And give examples.

Ans: Growth regulators can be classified under two categories;

a. Plant growth promoters. (Eg. Auxins, Gibberllins, and cytokinins).

b. Plant growth inhibitors. (Abscicic acid and Ethylene).

7. Enlist the functions of plant hormones or growth regulators.


a. Promote cell division, cell enlargement/elongation and cell differentiation.

b. Induce phototropic movement of shoot system.

c. Initiate the development of roots, flowers and fruits.

d. Control the falling of leaf, flower and fruits.

e. Control the premature withering of flowers and fruits.

f. Induce parthenocarpy (development of seed from flower without fertilization).

g. Break the dormancy of seeds and buds.

h. Delay ageing of leaves.

i. Control the opening of stomata.

8. What is a gland? Name the two types of glands.


Ans: Glands are special type of organs or a cell whose specialised for secretion.

Exocrine gland and endocrine gland.

9. What is endocrine system? Mention the important endocrine glands.

Ans: A group of ductless glands which secretes hormones is called endocrine system. Some important endocrine glands are;

a. Pituitary gland.

b. Thyroid gland.

c. Parathyroid gland.

d. Islets of Langerhans.

e. Adrenal gland and

f. Gonads (Testes and ovaries).

10. Name the two main ways of transferring information from one part of the body to another.

An: One way is by sending chemical signals through blood and other way is by sending electrical signals through the nerves.

11. What are hormones? Why hormones called chemical messengers?

Ans: Hormones are special type of chemicals which are secreted by endocrine glands. Hormones carry information from one part of the body to another through the blood. Hence hormones are called chemical messenger.

12. Mention the secretions of pituitary gland with their functions.


· Growth hormone (STH- Somatotropic hormone): It regulates both physical and mental growth.

· Thyroid stimulating hormone (TSH): It stimulates the secretion of hormones from thyroid gland.

· Adreno corticotropic hormone (ACTH): It regulates the secretion of hormones from adrenal glands.

· Melanocyte stimulating hormone (MSH): It controls the synthesis of melanin in skin.

· Prolactin: It stimulates the secretion of milk from mammary glands.

· Vasopressin: It controls the excretion of water from the kidneys.

· Oxytocin: It stimulates the constriction of uterus muscles during child birth and ejection of milk from mammary glands. It is also called ‘birth hormone’.

· Follicle stimulating hormone (FSH): It stimulates the production of gametes from gonads.

· Luteinizing hormone (LH): It stimulates the secretion of sex hormones by gonads.

13. What is gigantism and dwarfism?

Ans: When growth hormone is secreted in excess prior to sexual maturity, the growth will be very high and leads to gigantism.

When it is secreted in less quantity, it leads to dwarfism.

14. What is acromegaly? Mention their symptoms.

Ans: When growth hormone is secreted in excess even after maturity, it leads to a disorder
called acromegaly. The symptoms are protrusion of jaws and nose and disproportionate growth of bones in hands and legs.

15. Name the chemical present in thyroxin hormone. Mention the functions of thyroxin.

Ans: Thyroxin is an amino acid in combination with iodine.

Thyroxin influences the rate of metabolism, increases the heat, and promotes the mental and physical development of the body.

16. Why thyroxin is called the personality hormone?

Ans: Thyroxin promotes physical and mental development either directly or indirectly, hence it is called personality hormone.

17. Why is simple goitre due to? Can it be cured?

Ans: Due to the deficiency of iodine in the diet thyroid gland becomes swollen this condition is called simple goitre.

It can be cured by administrating the sufficient amount of iodine in the diet.

18. Which disease caused in children due to hypothyroidism? Mention the symptoms of that disease.

Ans: Children who are born without a properly functioning thyroid gland (hypothyroidism) they caused by the disease called cretinism.

Symptoms of this abnormality are stunted growth, retarded mental development, bow legs, defective teeth, protrusion of the tongue and loose, wrinkled skin with leathery texture.

Usually people living near coastal regions do not suffer from gpitrc.
We are using iodized salt for cooking food.

19. What is Myxedema?

Ans: The disease caused in adult due to the under activity of thyroid gland leads to low metabolic rate, loss of mental and physical vigour, increase in the body weight, thickness of the skin and lower rate of heartbeat.

20. What would happen if there is hyperthyroidism?

Ans: Excess of the thyroxin secreted from thyroid gland is called hyperthyroidism. This causes high metabolic rate, protrusion of the eye balls, high blood pressure, nervous tension, irritability, profuse sweating, fatigue and weight loss.

21. Write the functions of parathormone? How it causes in their deficiency and excess in quantity?

Ans: Parathormone is produced from the parathyroid gland. The function of paratharmone is to regulate the amount of calcium salts in blood and bones.

Deficiency of this hormone leads to painful muscles cramps and excessive secretion of it results in a loss of calcium in bones making them soft and spongy.

22. Name the hormones secreted in Islets of Langerhans?

Ans: Islets of Langerhans secret to hormones namely insulin and glucagon.

23. What is the function of insulin and glucagon?

Ans: Insulin promotes the conversion of glucose into glycogen, which is stored in liver and muscles.

Glucagon converts glycogen into the glucose.

24. How is diabetes mellitus caused? What are its symptoms?

An: Due to under secretion of insulin leads to increase in the level of glucose in the blood that is excreted through the urine. This condition is called diabetes mellitus.

The common symptoms of this disease are; Increased the glucose level in the blood, excretion of glucose through the urine, frequent urination, thirst, fatigue and sweating. This disease is can be controlled by administrating insulin injections.

25. Name the hormones secreted in adrenal glands.

Ans: Adrenal cortex - Secrete cortisone.

Adrenal medulla- Secretes three hormones; Adrenaline, Noradrenaline and dopamine.

26. Why the adrenaline hormone is called the emergency hormone?

Ans: Adrenaline secreted in excess quantity in emergency situations like fear, anxiety, anger and emotional stress and prepares the body to face the emergency situations properly. Hence it is called emergency hormone.

Adrenaline is also called fright, fight and flight hormone.

27. Why the simple goitre is an endemic disease?

Ans: It will never transmit from one person to another and it is restricted to a specific region.

28. What are gonads? What hormones do they secrete? What is their importance?

Ans: Gonads are sex cells (gametes) secreting and sex hormones secreting glands.

Testes produce hormones called androgens. The most common among them is testosterone. This hormone is responsible for the appearance of masculine characters in males.

Ovaries produce female hormones called estrogens. This hormone is responsible for the appearance of feminine characters in females after puberty. Ovaries also secrete a hormone called progesterone. This hormone stimulates the changes in the uterus during menstrual cycle and pregnancy.

29. What is nervous system? What is its importance?

Ans: System which helps in controlling and coordinating various activities and functions in the body that enables an organism to respond to various stimuli.

Importance of nervous system:

· It controls and coordinates various activities and functions in the body.

· It regulates both voluntary and involuntary activities of the body.

· It controls all the reflex action of the body.

· It enables us to think, reasoning and remember.

30. What is a neuron? Mention the three types of neurons.

Ans: A neuron is a special type of cell that is the basic, structural and functional unit of nervous system. There are three types of neurons; they are,

Sensory neuron, motor neuron, mixed neuron.

31. Mention the functional components associated with nervous system.

Ans: The functional components associated with nervous system are;

Receptors - The organs that receive stimuli. Eg: Sense organs.

Effectors - The organs which show visible response. Eg: Muscles and glands.

Conductors - The tissue which connect the receptors and effectors and helps in the transmission of impulses. Eg: Nerves.

32. Name the three main divisions of nervous system in men.

Ans: Central nervous system [CNS]

Peripheral nervous system [PNS]

Autonomic nervous system [ANS]

33. What are meninges?

Ans: Both brain and spinal cord is surrounded by three membranes, outer duramater, and middle arachnoid and inner piamater. They are together called meninges.

34. Mention the main parts (divisions) of brain.

Ans: Human brain extremely shows three distinct parts. They are forebrain, midbrain and hind brain.

35. Why the cerebrum called seat of consciousness?

Ans: Because the cerebrum has the centre for intelligence, imagination, emotions, reasoning and will power. And stores the information, which are gained through the sense organs.

36. What is Corpus Callasum?

Ans: A sheath of nerve fibres which internally connects the cerebral hemisphere is called Corpus Callasum.

37. Name the two parts of cerebrum.

Ans: Outer cortex - Composed of cytons and forms the grey matter.

Inner Medulla - Composed of nerve fibres (axons and dendrite) and forms the white matter.

38. What is memory?

Ans: The information gained through the sense organs is stored in the cerebral cells and is used whenever required. This is called memory.

39. Name the two parts of diencephalon. Mention their functions.

Ans: Diencephalon has two parts namely; thalamus and hypothalamus.

Thalamus: That receives nerve impulses from many sense organs and sends them to cortex. Hypothalamus: It regulates body temperature, water balance, appetite and sleep. It also controls autonomic nervous system and pituitary gland.

40. Mention the three main parts of the hind brain. Write their functions.

Ans: Hind brain has three parts namely, cerebellum, Pons varolii and medulla oblongata.

Cerebellum is the second largest part of the brain. It controls and coordinates the movement of muscles while walking or running. Hence it is responsible for maintenance of the balance of the body.

Pons: It regulates mastication, facial expression and respiration.

Medulla oblongata: It is concerned with involuntary activities like breathing, heartbeat, movements of the digestive tract (swallowing, coughing, and vomiting). It is also involved in the secretion of enzymes and maintaining blood pressure.

41. What is reflex action? Give an example. What is their advantage?

Ans: A sudden or automatic response to external stimuli is called reflex action.

Many accidents can be avoided because of the speed of the response.

When you touch something hot, without any thinking you move your hand away. This prevents you burning your hand. Also when you see a car your first response is you moving away.


42. What is reflex arc? Mention its five components.

Ans: The pathway of nerve impulses involved in the reflex action is called a reflex arc.


· Receptor which receives the stimuli.

· Sensory neuron (afferent neuron) that conduct the stimulus impulse from the receptor to the spinal card.

· An association neuron which transmits the impulse from the sensory neuron to the motor neuron.

· Motor neuron (efferent neuron) which conducts response impulse from spinal card to the effectors.

· An Effector, which shows the sudden response.

43. What peripheral nervous system includes?

Ans: It includes 12 pairs of cranial nerves and 31 pairs of spinal nerves.

44. What is autonomic nervous system? What are its two main divisions?

Ans: Involuntary organs are connected and controlled by a set of peripheral nerves. This is called, autonomic nervous system.

Autonomic nervous system consists of sympathetic and parasympathetic nervous system, which control opposite actions of parts or organs in the body. For example, when sympathetic nervous system stimulates the dilation of pupil of the eye, parasympathetic nervous system controls the constriction of the same.

45. Why a drunkard walks unsteadily?

Ans: Alcohol effects on cerebellum, which is responsible for maintenance of the balance of the body. So it causes a drunkard to walks unsteadily.

Exposure to alcohol during development and chronic consumption leads to hypoplasia / dysgenesis of cerebellum.

46. An injury to left cerebral hemisphere leads to the paralysis of parts in the right side of the body why?

Ans: Because the nerves from left side of the body are connected to right cerebral hemisphere and nerves from the right side of the body cross over in the neck and are connected to left cerebral hemisphere. So if left hemisphere gets injured leads to paralysis of parts in the right side of the body.

47. What are sense organs?

Ans: Organs which receives the stimulus from the environment are called sense organs.

Eg. Eyes, ears, nose, tongue and skin.

48. What is lacrymal gland?

Ans: The gland situated on the inner surface of the upper eyelid, responsible for the secretion of the tear is called lacrymal glands (tear glands).

49. Name the layers of the human eye?

Ans: Outer sclera, middle choroid and inner retina.

50. What is Iris? Mention its function?

Ans: The muscular layer formed by the choroid which surrounds the pupil in front of the eye is called iris. It has pigment cells that are responsible for different colour of the eyes.

51. Name the two receptors present in retina with their functions.

Ans: Retina has the visual receptors namely, rods and cones.

Rods are sensitive to light and cannot distinguish colours where as cones are sensitive to bright light and can distinguish the colour.

52. What is blind spot?

Ans: A part of the eye where the image is not formed due to the absence of sensory cells is called blind spot. It present near the optic nerves.

53. Write the functioning or mechanism of the human eye.

Ans: The reflected light rays from the object enter the eyeball through the conjunctiva, cornea, pupil and lens and get focus on the fovea of retina to form a small, real and inverted image. The visual receptors (rods and cones) get stimulated by photochemical reactions and convert images into the electrical impulses. These impulses are carried through the optic nerve to the visual centre where they get interpreted. It results in vision.

54. What is accommodation of the eye?


Ans: When we see a distant object, the convexity of the lens decreases and the eyeball becomes flat. On the other hand, when we see any nearer object the convexity of the lens increases and the eyeball gets bulged. This capacity of the lens is called accommodation of the eye.

55. What is myopia and hypermetropia? How are they corrected? Show with the help of diagram?

Ans: Myopia- this is the condition of eye where the distant objects appear blurred it is also called short sightedness. In this case the image of the distant object is formed in front of the retina due to the bulging of the eyeball or increasing of the convexity of the lens. This defect can be corrected by using a concave lens of a suitable focal length.

Hypermetropia or far sightedness is the condition of appearance of near objects blurred. In this case the image of the object is formed behind the retina due to the constriction of the eyeball or decreasing of the convexity of the lens. This can be corrected by using convex lens.


56. What is Presbyopia?

Ans: In some aged people, the lens may lose its elasticity then it becomes rigid and results in a kind of farsightedness. This condition is called Presbyopia. This can be corrected by using convex lens.

57. What is cataract?

Ans: Blurring of vision due to the formation of a layer on eyeball is called cataract.

58. What is diabetes retinopathy? How it be cured?

Ans: In diabetes patient blood capillaries in the retina may rapture and causing blood entering the vitreous humour and the making it opaque. This leads to blindness. This disease is called diabetes retinopathy.

This disorder can be cured by laser treatment or a surgery called vitrectomy.

59. How the astigmatism and glaucoma caused? How it be cured?

Ans: Astigmatism is a condition, in some people a part of the images formed on the retina is blurred due to the unevenness of the refractive surface of the eye such as lens or cornea. This condition is called astigmatism.

This can be corrected by using suitable cylindrical lens.

In some people who are aged above 40 - 45 years may be suffering from a serious disease of the eye which would often lead to total blindness. This is mainly due to gradual hardening of the eyeball, this is called Glaucoma. The person suffering from this disease may first see flashes of light and coloured rings around object. This can be cured in early stages by medicines and in advanced stages, a surgery may be required.

60. How you removed the foreign bodies which enter into your eyes?

Ans: Foreign bodies such as flies, dust particles, pieces of metals or wood may enter the eye. In such cases, eyes should not be rubbed which would further worsen the condition.

If the foreign body is visible, it can be removed using clean hand kerchief or a piece of cloth.

It can also be removed by continuously blinking eyes.

For some time by immersing the eyes in a bowl of clean water or boric solution.

61. How you care about your eyes?


· Do not strain eyes by reading books with very small letters in dim light for long time.

· Do not read books during journeys on roads.

· Avoid direct bright light.

· Eyes should be washed with clean and cold water at least twice a day.

· Avoid watching television from a very short distance for a long time.

· Avoid working on computer with monitor for a long time.

· In any case of emergency, consult the eye specialist. Avoid self medication.

62. Briefly explain the structure of inner ear.


Ans: The entire ear is filled with fluid is called endolymph and surrounded by another fluid is called perilymph. The inner ear has two main parts namely upper utriculus and lower sacculus. The utriculus leads to a set of three se micircular canals and sacculus leads to a coiled or spiral structure called cochlea. Semicircular canals and cochlea are concerned with the balancing of the body. Cochlea occupies a large space in the inner ear and encloses a very delicate structure called organ of corti. It has sound receptor cells. All these cells connect to form a sensory nerve of the ear called auditory nerve. That carries the sound impulses to the auditory centre of the cerebrum.

63. Write the mechanism of hearing.

Ans: The sound waves from the source are directed by the ear pinna to the eardrum through the auditory canal.

The eardrum vibrates and these vibrations are transmitted to the inner ear through the chain of bones of the middle ear.

The vibrations are further transmitted to the organ of corti of the cochlea through both perilymph and endolymph.

The receptors present in the organ of corti absorb these sound impulses which are then carried by the auditory nerve to the auditory centre of the cerebrum. Here they are interpreted and sound is heard.

64. How you care about your ears.


· Remove the wax by using safe ear buds. It should not be removed using hard and sharp objects which may damage the eardrum.

· Loud noise should be avoided as it may hamper hearing. Plug the ears with soft cotton or use ear plugs.

· Common cold or throat infection sometimes leads to the infection of the middle ear.

· Some people are born deaf due to congenital defects. Even old age causes deafness. A hearing aid prescribed by the specialist may correct the condition.

· Small insects or worms entering the ears can be easily removed by filling the auditory canal with lukewarm saline water. Do not use oil.

65. What are taste buds?

Ans: The sensory cells for taste and distributed on the surface of tongue in the form of taste buds. They are embedded in the mucous membrane.

66. How the brain or cerebrum interprets the impulses of test?

Ans: When food passes on the surface of the tongue, the sensory cells are chemically stimulated. The chemical impulses are converted into electrical impulses. They are carried by the sensory nerve the cerebrum of the brain where test is interpreted.

67. Name the four basic types of tastes?

Ans: Basic types of tastes are sweet, salt, sour and bitter.

68. There is no image formation at blind spot. Give reason.

Ans: Blind spot doesn’t contain any visual receptor such as rods and cones. Hence there is no image formation.

69. A concave lens is used to correct Myopia. Why?

Ans: Myopia is caused by increasing the convexity of lens (bulging of lens). So it is modified or corrected by concave lens of a suitable focal length.

70. Throat infection often results in ear pain. Give reason.

Ans: The middle ear is connected with the throat region through a tubular passage called eustachian canal. This passage leads the infections into the ear and causes the pain whiles them growing.

71. It takes some time to see the objects clearly when we enter a dark room from a bright area.

Ans: Because, to see anything, there must be a definite amount of light going up to the cornea through the pupil. In brightness, pupil constricts to restrict amount of light going in. When we suddenly move from dark to brightness, pupil constrict, eye squint and it hurts. So it takes time to dilate.

72. Draw a neat labelled diagram of spinal cord.


73. Draw a neat labelled diagram of longitudinal section of human eye.


74. Explain the structure of human eye.

Ans: Human eye ball is spherical and covered by three layers. Namely; sclera, choroid and retina. Sclera is the outermost layer. The bulged, thin, transparent front part of the eye ball is called cornea. It is encloses by a transparent protective layer called conjunctiva.

Choroid is richly supplied by nerves and blood vessels, forms muscular layer around the pupil called Iris. It has pigment cells responsible for eye colour.

Inner most layer is retina, has depression called fovea (yellow spot).

Lens is held in position by suspensory ligaments and ciliary muscles.

Transparent, clear fluids called aqueous humour and vitreous humour present in front and behind the lens respectively.


Exocrine glands

Endocrine glands

Glands secrete the hormones, reaches the target organ through the ducts.

Glands secrete the hormones, reaches the target organ through the blood stream.



It is a male sex hormone, responsible for masculine characteristics.

It is a female sex hormone, responsible for feminine character.

Grey matter

White matter

Part of brain and spinal cord composed of cytons.

Part of brain and spinal cord composed of nerve fibres (axons and dendrites).



Largest part of the brain. It has centres of intelligence, imagination, emotions, reasoning and will power.

Second largest of the brain. I is responsible maintenance of the balance of the body.

Sensory nerve

Motor nerve

Nerve which carries stimulus from receptors to brain or spinal cord.

Nerve which carries response from brain or spinal cord to effectors.

Cranial nerves

Spinal nerves

Nerves which are originated from cranium or brain are called cranial nerves. 12 pairs of cranial nerves are present in humans.

Nerves which are originated from the spinal cord are called spinal nerves. 31 pairs of spinal nerves are present in humans.

Sympathetic nervous system

Para sympathetic nervous system

Control involuntary action, work opposite to the Para sympathetic nervous system.

Ex: Stimulate the dilation of pupil of the eye.

Control involuntary action, work opposite to the sympathetic nervous system.

Ex: Controls the constriction of pupil of the eye.

75. Draw a neat labelled diagram of human ear..


76. Sketch a neat labelled diagram of human brain.




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