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Q  1. Expand the terms CNS and PNS.

Solution

i. CNS - Central Nervous System ii. PNS - Peripheral Nervous System

Q  2. How does feedback mechanism regulate the hormone secretion?

Solution

The feedback mechanism regulates the timing and amount of hormone to be secreted in our body. For example, if a person has more sugar in his blood, this is detected by the cells of the pancreas. As a result, more insulin will be secreted to oxidize the sugar. In a reverse situation the secretion of insulin will be depleted.

Q  3. Name any three endocrine glands in human body and briefly write the function of each of them.

Solution

The three endocrine glands in human body are : i.Thyroid: It plays a major role in regulating the body's metabolism. ii.Pancreas: It secrets hormones that affect the level of sugar in the blood. iii.Pituitary: It secrets Growth hormone.

Q  4. What are voluntary actions? How their functioning is controlled?

Solution

The actions that are performed by the will or choice of an individual are known as voluntary actions. In this case, the responses of individual vary a lot. The cerebellum of hind brain controls all these actions.

Q  5. State the sequence of changes that take place in a human body when it prepares itself to protect from a scary or dangerous situation.

Solution

When the organism confronts any scary situation, adrenalin is secreted from the adrenal gland and sent directly into the blood which is then circulated to various parts of the body, resulting in the following :- (a) The main target organs include the heart- the heart beats faster resulting in more amount of oxygen supplied to the muscles. (b) The blood supplied to digestive system and the skin is reduced due to contraction of muscles around small arteries. This diverts the blood to the skeletal muscles. (c) The breathing rate also increases because of the contractions of the diaphragm and rib muscles.

Q  6. Expand FSH and LH.

Solution

i. FSH - Follicle Stimulating Hormone ii. LH - Luteinizing Hormone

Q  7. How is brain protected from shocks and injuries?

Solution

The brain box called cranium protects the brain and has shock absorbing fluid in it which prevents it from shock and injuries.

Q  8. Generally some of teenagers readily come under bad influences under peer group pressure. (i) Why do teenagers readily come under this influence? (ii) Suggest methods to overcome such problems.

Solution

(i) Adolescence brings about the hormonal secretion among teenagers. This leads to some physical and emotional changes among them which are difficult to bear. (ii) a. Proper counseling of teenagers should be arranged from the counsellor. b. Healthy communication with parents. c. Teenagers should be properly motivated to set realistic goals.

Q  9. What are neurons?

Solution

Neurons are the nerve cells that altogether constitute the nervous system and help in the transmission of information from one part of body to another.

Q  10. (a) What is the structural and functional unit of nervous system ? Name any of its two components. (b) Which structure in a neuron helps to conduct a nerve impulse : (i) towards the cell body. (ii) away from the body.

Solution

(a) Neuron is the structural and functional unit of nervous system. Components - Cell body, Dendrite, Axon. (Any two) (b) (i) Dendrites carry the nerve impulse towards the cell body. (ii) Axons carry the nerve impulse away from the cell body.

Q  11. What are nastic movements? Describe its various types briefly.

Solution

The directionless movements of plants caused due to the external variations in environment are termed as nastic movements. Various types of nastic movements are: i. Seismonsatic movements: The movement of a plant or its part in response to touch or any kind of shock. Example - the folding or drooping of leaves of ‘touch-me-not’ plant. ii. Nyctinastic movements: The movements of plants that occur in response to presence or absence of light (photonastic movements) or variation in temperature (thermonastic movements).

Q  12. Describe briefly about the autonomic nervous system.

Solution

Autonomic nervous system is a part of peripheral nervous system which is responsible for involuntary actions i.e. it regulates all those actions or responses of our body that are not according to our will. Example - beating of heart. It has two parts: i. Sympathetic nervous system ii. Parasympathetic nervous system The nerve fibres of both these parts have opposing effects i.e. if one stimulates a particular response, the muscles of other system inhibits that response.

Q  13. Briefly explain the reflex arc.

Solution

In case of reflex actions, the path followed when a message is transmitted to spinal cord and then the instruction is passed to the muscle (effector) forms a reflex arc. For example, in case when a hot object is touched to our hand, thermoreceptors present in skin transmit nerve impulses to spinal cord form where they are sent to motor neuron. The motor neuron further passes them in the form of instruction to the muscle that show response as per the instruction.

Q  14. Which receptor detects or perceives the stimulus of cold?

Solution

The stimulus of cold is perceived by the thermoreceptors present in our skin.

Q  15. What is geotropism?

Solution

The movement of roots of plants towards the gravity i.e. downwards is termed as geotropism.

Q  16. 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.

Solution

The 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 chemical impulse in a dendrite of the next neuron.

Q  17. Give reasons: i. (a) Pituitary is often termed as master endocrine gland. (b) Pancreas helps in digestion and also regulates blood sugar level. (c) Adrenals are known as glands of emergency. ii. Name the part of hind brain which controls involuntary actions.

Solution

i. (a) Pituitary gland is often termed as master gland because it controls the secretion of all other endocrine glands. (b) Pancreas secretes digestive enzymes which help in digestion and hormone, insulin which regulates blood sugar level. (c) During emergency conditions, when a person is excited or frightened, adrenal gland secretes adrenaline hormone in large amounts which prepares our body for action. It speeds up heart beat and breathing, raises blood pressure and allows glucose to go more into the blood to give a lot of energy. So, it is often known as glands of emergency.  ii. Medulla controls various involuntary actions such as heart beat, blood pressure, etc.

Q  18. Describe the process of homeostasis and how it takes place in our body?

Solution

The phenomenon by which the internal chemical environment of our body is maintained and remains constant irrespective of changes in the outside environment is known as homeostasis. Hormonal action and feedback control help in maintaining homeostasis. The feedback control can be either: Positive feedback control: It slows down the production of a hormone. . Negative feedback control: It leads to an increase in the production of a hormone.

Q  19. Give a reason to explain why: (i) Adrenaline helps in dealing emergency situations? (ii) Secretions of growth hormone should be specific in the human body? (iii) Some patients of diabetes are treated by giving injections of insulin?

Solution

(i) Adrenaline increases the heart beat and breathing rate which results in the supply of more oxygen to muscles. It reduces the blood to the digestive system and skin; as a result the blood further reaches the skeletal muscles. All these responses together prepare the body to deal with the emergency situations. (ii) If growth hormone is secreted in excess during childhood, then it leads to gigantism while the less secretion of this hormone during childhood causes dwarfism. (iii) The patients suffering from diabetes have high blood sugar level as insulin is not secreted in sufficient amount by the pancreas which lowers the blood sugar level. Therefore, to regulate the blood sugar level, insulin hormone is injected in such patients.

Q  20. Name two phytohormones and write any two functions of each.

Solution

i. Auxin - cell enlargement, promotes growth , root formation. ii. Gibberellins - Stem elongation, seeds germination, flowering.

Q  21. What happens at the synapse between two neurons?

Solution

A stimulus received by a neuron travels through it in the form of an electrochemical disturbance. When an electrical signal reaches the axonal end of one neuron, it releases chemical substance called neurotransmitter that cross the synapse and move towards the dendritic end of next neuron generating another electrical signal. A narrow fluid filled space, called synaptic cleft occurs between the two neurons. An impulse travels through the neurons only in one direction because the neurotransmitter is released only on one side of the synapse.

Q  22. Ram has met with an accident after that he lost the capacity to (i) Walk in straight line (ii) Smell anything (iii) Does not feel full after eating. Which part of brain is damaged in each case?

Solution

(i) Hind brain /cerebellum (ii) Fore brain (iii) Fore brain

Q  23. Name any one hormone secreted by pancreas.

Solution

Insulin is secreted by pancreas.

Q  24. Which gland secretes the growth hormone? What will happen if growth

hormone is secreted in improper amount?

Solution

Growth hormone is secreted by pituitary gland. Following disorders are caused due to the improper secretion of growth hormone: i. Dwarfism: This disorder is caused when there is deficiency of growth hormone at an early age. ii. Gigantism: This disorder is caused due to the excess secretion of growth hormone at an early age. iii. Acromegaly: This disorder is caused when growth hormone is secreted in excess after adolescence.

Q  25. Name major parts of brain.

Solution

The brain is divided into three regions: forebrain, midbrain and hindbrain.

Q  26. How are involuntary actions different from reflex actions?

Solution

Involuntary actions are the actions which cannot be controlled by us if we want to do so. There is no external stimulus involved. The action takes place on its own like digestion, heart beat, etc. Reflex action is a kind of involuntary action which is controlled by and occurs due to an external stimulus. Its response to the stimulus is quick. Example - sneezing, blinking of eyes, etc.

Q  27. Describe the functions of different regions of brain.

Solution

The functions of different regions of brain are as follows: i. Forebrain -  a) It is the greatest part of brain and has different centres to receive impulses from sense organs and also from the muscles. b) Forebrain stores information and experiences perceived by senses and help in making associations from them. ii. Midbrain - The midbrain controls all the reflex actions shown by different parts of our body.   iii. Hind brain - a) The main function of hind brain is to maintain the muscle tone and balance of our body. b) It also regulates the heart beat, movement of blood vessels, swallowing and sneezing.

Q  28. What is meant by plant hormone? Give one example each of plant hormone that : (a) Promotes growth. (b) Promotes cell division. (c) Inhibits growth. (d) Promote the growth of a tendril around a support.

Solution

Plant hormone: In plants some chemicals stimulate growth while some others retard the rate of growth. Such chemicals are termed as plant hormones. (a) Auxin (b) Cytokinins (c) Abscisic Acid (d) Auxin

Q  29. Explain how the transmission of information (nerve impulses) takes place across different neurons.

Solution

The transmission of nerve impulse from one neuron to another one takes place through the synapse, a minute gap between the nerve ending of one neuron and the dendrites of another neuron. The signal is first detected by the dendrites and then transmitted to the cell body, from where it reaches the nerve ending via the axon. From the nerve ending through the synapse it travels to another neuron.

Q  30. Write the cause and symptom of diabetes mellitus.

Solution

Cause: Diabetes mellitus is caused due to the lack of insulin hormone due to which the blood glucose level is not regulated. Symptoms: Person excretes sugar in urine, feels excessive thirst.

Q  31. What is the function of receptors in human body? Name two types of receptors found in humans. What problems are likely to occur if receptors do not work properly?

Solution

The function of receptors is to receive external stimuli. The receptors found in humans are: Gustatory receptors to taste and Olfactory receptors to smell. If receptors do not work then organisms will fail to receive stimuli and so fail to respond.

Q  32. Describe the nerves of the peripheral nervous system

Solution

The peripheral nervous system consists of two types of nerves: Cranial nerves: Which arise from the brain and spread to all body parts. Spinal nerves: Which arise from the spinal cord and spread all over the body. These are mixed nerves.

Q  33. What is a receptor?

Solution

The group of nerve cells or a single cell that detects or receives the stimulus or any kind of change in the environment is known as receptor.

Q  34. In living organisms, which tissue provides the control and co-ordination in their bodies?

Solution

Control and co-ordination is provided by nervous and muscular tissue.

Q  35. Tendril encircles or coils around the object in contact with it. Elaborate.

Solution

Auxin diffuses to the other part which is away from the support. Part of the tendril in contact from the support does not grow rapidly. Part of the tendril away from the support grow rapidly and cause the tendril to grow around a support.

Q  36. Write the functions of parts of hind brain.

Solution

Hind brain has three parts: (i) Cerebellum: It is the regulating centre for swallowing, coughing, sneezing and vomiting and helps to maintain the balance of the body and coordinate the muscular activities. (ii) Pons: It takes part in the regulation of respiration. (iii) Medulla oblongata: It is responsible for the coordination and adjustment of movement and posture.

Q  37. What do we call the movement of shoot towards light?

Solution

Phototropism is the direction of growth of a plant in response to the direction of the light.

Q  38. What is a reflex action?

Solution

The involuntary, spontaneous and automatic responses shown by our body (effector) in response to stimulus perceived by receptors (sense organs) are termed as reflex actions.

Q  39. (a) What is reflex arc?

(b) How do muscle cells move?

Solution

(a) The pathway taken by a stimulus to travel from receptor organ to effector organ is called reflex arc. (b) Muscle cells have special proteins that change their shape and arrangement in the cell in response to electrical impulses. This leads to the shortening of muscle.

Q  40. Explain the functioning of sensory receptors.

Solution

The sensory receptors first collect information (stimulus) from the environment which acts as electrical impulses. These electrical impulses or sensations are carried either to brain or spinal cord and are analysed there and then the result (instruction) in the form of motor impulses is sent to the muscle or effector.