1. Mention three important functions of gibberellins.
Ans. Functions of Gibberllins –
(i) Stimulate stem elongation.
(ii) Help in breaking seed dormancy.
(iii) Promote flowering in some plants even under unfavorable conditions
(iv) Help in seed germination.
(v) Promote production of male flowers
.
2. What is the function of receptors in our body? What happens when receptors do not work properly?
Ans. The function of receptors is to defect information form the environment. If receptors do not work properly, the information obtained form 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.
3. What happens at the synapse between two neurons?
Ans. The nerve impulse gets transmitted through the synapse by means of chemical signals. When a stimulus acts on the receptor, chemical reaction is set off which produces an impulse in it. This impulse travels form the dendrite of presynaptic neuron to its cell body and then along its axon. At the end of axon of this neuron, the electrical impulse releases tiny amount of a chemical substance crosses the synapse and starts a similar electrical impulse in the dendrite of the next neuron.
4. What is the need for a system of control and co – ordination in an organism?
Ans. a) It evokes an appropriate movement in response to any change in external environment
b) Multicellular organisms have complex body. So it, co – ordinates various organs of body of an organism work together in a proper manner to produce proper reaction to stimulus
5. Pituitary is a master endocrine gland. Justify this statement.
Ans. Pituitary gland is also known as master gland because it controls the activities of most of the gland.
It regulates the secretion of other glands. Like-
a) Growth hormones – Body growth and development of bones
b) Thyroid stimulating hormone – Secretion of hormones form thyroid gland.
c) Adrenocorticotropic hormone – Secretion of hormones form adrenal glands.
d) Follicle stimulating hormone – Stimulating of growth of ovaries and testes
e) Luteinsing hormone – Secretion of hormone from ovaries & testes
f) prolactin – Regulation of function of mammary gland. Hence, most of functions are controlled by pituitary gland so it is called master gland.
6. Draw the structure of neuron and explain its function.
Ans. Neuron has three components –
(i) Cell body
(ii) Dendrites
(iii) Axon
The dendrite picks up the nerve impulse from receptors and then pass the impulses to the cell body and then along the axon. The axon passes the impulse to another neuron through a junction called synapse.
7. How does our body respond when adrenaline is secreted into the blood?
Ans. When adrenaline is secreted into the blood, it prepares our body for action. It speeds up heart beat and breathing, raises blood pressure and allows more glucose to go into the blood to give us a lot of energy quickly to fight or urn away from frightening situation. The blood supply decreases form the skin and digestive system and increase to skeletal muscles. All there conditions help the individual to respond the emergency situation.
8. Where are Pons and medulla oblongata located? Write their functions.
Ans. Pons and medulla Oblongata are located in hind brain. Pons acts as bridge between brain and spinal cord. Medulla oblongata –
a) It is the reflex centre to control activities like salivation, swallowing, vomiting, breathing, coughing, sneezing and heart beat
b) It also controls sleeps, consciousness and activities of cerebrum
9. List the function of testosterone and estrogen. Where are they secreted?
Ans. Testosterone is secreted in males – It is responsible for development of male sex organs and secondary sex characteristics like moustache, beard & voice. Estrogen is secreted in females – it is responsible for development of female sex organs and secondary sex characteristics like mammary gland and uterine growth.
10. Define ‘nerve impulse’. Which structure in a neuron helps to conduct a nerve impulse?
a) Towards the cell body?
b) Away from the cell body?
Ans. Nerve Impulse – It is the passing of information through neurons is in the form of electrical and chemical signals. This is called nerve impulse.
a) Dendrite
b) Axon
13. What are tropic movements? Name the types of tropic movements in plants.
Ans. The bending or movement of a part of plant in response to the external stimulus is called tropism or tropical movement. It is of following types.
(a) Phototropism – It is response to light. It may be towards light (positive) or away from the light (negative).
(b) Geotropism – It is response to gravity – It may be towards stimulus (positive) and away from the stimulus (negative)
(c) Chemotropism - Response to chemicals. It may be positive or negative.
(d) Hydrotropism – Response to water. It may be positive or negative.
14. Name the different lobes of cerebrum.
Ans. Different lobes of cerebrum –
a) Frontal lobe – It is associated with reasoning.
b) Parietal – Perception of general sensation s like pressure, touch and pain.
c) Occipital – Visual perception.
d) Temporal – Important for interpreting sounds and the language we hear and formation of memories.
15. How do auxins promote the growth of tendril around a support?
Ans. 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 form the support, auxins promote growth. So, due to more auxins in it, the side of tendril, away from the support, grow faster and becomes longer than the side which is in contact with the support and makes the tendril curve towards the support.
17. What are the different kinds of neurons?
Ans. Kinds of neurons –
a) Sensory neurons – convey impulses from receptors to the main nervous system.
b) Motor neurons – carry impulses from the main nervous system to an effector.
c) Connecting (Relay) neurons – connect sensory and motor centres.
18. How does chemical co-ordination takes place in animals. Mention their function.
Ans. The chemical co – ordination in animals takes place through hormonal system called endocrine system. Animal hormones are chemical messengers which are directly poured into the blood by the endocrine glands. Thus, a hormone reaches to the cells. The cells have special molecules on their surface to detect these chemical compounds and recognize the information a particular hormone carrying. There the cells act accordingly. The chemical co – ordination is fast as hormones diffuse readily around the cells
20. Nervous and hormonal system together performs the functions of control and co – ordination in human beings. Justify the statement.
Ans. A number of interactions between the environment and the animal are a result of combined action of both neurons and endocrine system for which specialized tissues are used to provide control and co – ordinations activities.
21. What is the difference between a reflex action and walking?
Ans.Reflex action.
a.Take place without thought
b.controlled by spinal cord
c.It is involuntary action
Walking
a.Takes place after thought
b.Controlled by cerebellum.
c.It is a voluntary action.
22. What happens at the synapse between two neurons?
Ans. At synapse, the electrical impulse generated a dendrite of a neuron is passed on to dendrite of another neuron in form of chemical impulses. The chemical present at synapse is called neurotransmier.
23. How do auxins promote the growth of a tendril around a support?
Ans. When tendrils come in contact of any support, the part of the tendril in contact does not grow as rapidly as the part away from the object due to auxin secreted moves away from the object in contact. This rapid growth on one side causes tendril to circle around the object.
24. Design an experiment to demonstrate hydrotropism.
Ans. Take a tin box with hole at bottom. Fill it with moist saw dust. Sow some gram seeds in it. Keep the tin box in tilted position. When seeds start germinating, water the saw dust only in lower side of the tin box. You will observe that the radicle move towards the wet saw dust. This shows that root is positively hydrotropic.
25. How does our body respond when adrenaline is secreted into the blood?
Ans. When adrenaline reaches the various target organ through blood. All these organs respond together to enable our body to deal with situation like running away from scary situation. When adrenaline reaches the heart, it beats faster to supply more oxygen to our muscles. The small arteries around digestive system and skins contracts to divert the blood towards muscles. All these response enable our body to deal with situation.
26. Why are some patients of diabetes treated by giving injections of insulin?
Ans. Diabetes is caused due to non or less secretion of hormone insulin by pancreas. In such person, the blood sugar level is high. Insulin converts extra sugar present in blood into glycogen. Patients suffering from diabetes are given insulin injection to control their blood sugar level.
27. What is the function of receptors in our body? Think of situation where receptors do not work properly. What problems are likely to arise?
Ans. Receptors detect all the information from our environment. These receptors are located in our sense organs. In case any of the receptors do not work properly we will not be able to perceive that particular information.
28. How phototropism does occur in plants?
Ans. Movement of shoot towards light is called phototropism. This movement is caused due to more growth of cells towards the shaded side of the shoot as compared to the side of shoot towards light. More growth of cells is due to secretion of auxin towards the shaded side.
29. Which signals will get disrupted in case of a spinal cord injury?
Ans. (i) Reflex action
(ii) Impulses from various body parts will not conducted to brain.
(iii) Message from brain will not be conducted to various organs.
30. How does chemical coordination occurs in plants?
Ans. Chemical coordination in plants is maintained by plant hormones also known as phytohormones. Some of these hormones promote growth while some inhibit it. Some hormones include auxin, Gibberellins, Cytokinin etc.
31. What is the need for a system of control and coordination in an organism?
Ans. An organism has different organs which perform various factions. The survival of an organism depends on integrated and coordinated functions of these organs. Nervous and endocrine system of an organism makes them work together like parts of one machine to accomplish homeostasis or coordination.
32. How are involuntary actions and reflex actions different from each other?
Ans. Difference between involuntary and reflex actions is as follows Involuntary Actions:It is a set of muscles movement over which we do not have control.Such actions are controlled by brain.For example contraction of muscle of our digestive tract,beating of heart etc.
Reflex Action:It is rapid, spontaneous and involuntary activity that is produced in response to a stimulus.It is controlled by spinal cord.Example-removal of hand with jerk when someone touches a hot object.
33. Compare and contrast nervous system and hormonal control and coordination in animals.
Ans. Nervous control
a.Consists of nerve impulses conducted by neurons from one organ to another organ.
b.Nervous impulses produce rapid short lasting responses.
c.Nervous impulses are not specific in their action
Hormonal control
a.It consists of endocrine system which secretes chemical messengers hormones secreted directly in blood
b.Hormones produce longer lasting reponses
c.Action of hormones is highly specific
35. On touching a hot plate, you suddenly withdraw your hand. Which category of neurons became active first and which one next?
Ans. On touching a hot plate, first the sensory neurons are activated, which take the information to the brain or the spinal cord. Next, the motor neurons become active and bring the impulses from the brain to the muscles. In receiving these impulses, the muscles contract, and the hand is immediately removed from the hot plate.
36. How does the plant shoot bends, when the plant is placed in a room having only one open window?
Ans. When the plant is placed in such a room that has only one open window, the shoot of the plant bends towards the direction of light. Plant hormone axing is formed that diffuses towards the shady side of the shoot and stimulates the cells to live longer on the side of the shoot which is away from light. In this way the shoot bends towards the light.
37. Give a reason to explain why
(a) adrenaline helps in dealing emergency situations?
(b) secretions of growth hormone should be specific in the human body?
Ans. a. 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 is further diverted to skeletal muscles. All these responses together prepare the body to deal with the emergency situations.
b. If growth hormones is secreted in excess during childhood then it leads to gigantism while the less secretion of this hormone during childhood causes dwarfism.
38. A man becomes unconscious due to head injury. A pin is pricked on his foot, he withdraws his foot. Why? Explain.
Ans. It is reflex action. Stimulus is perceived by receptor (skin). Sensory nerve sends the sensation from receptor to the spinal cord. Then spinal cord sends the message through motor nerves to the effectors. Effectors i.e. muscles help in withdrawing his foot.
2. Mention one function for each of these hormones.
i) Thyroxine
ii) Insulin
iii) Adrenaline
iv) Growth hormone
v) Testosterone.
Ans. (i) Thyroxin – Control overall metabolic rate of the body (carbohydrate, protein and fat metabolism)
(ii) Insulin – Conversion of glucose to glycogen in liver and muscles, thus decreases blood glucose level.
(iii) Adrenalin – increases heart beat, blood pressure and blood glucose level.
(iv) Growth hormone – Body growth and development of bones.
(v) Testosterone – Development of male sex organ sand secondary sex characteristics like moustache, beard & voice.
3. a) what are hormones?
b) list four characteristics of hormones
Ans. Hormones are chemical substances which are secreted in very less amount by specialized tissues called endocrine glands. Characteristics of hormones are –
1) They are required in very less amount.
2) Hormones are specific in their function.
3) They act away from the site of production.
4) Deficiency or over secretions of hormones have negative effects in the body.
4. Design an experiment to demonstrate hydrotropism.
Ans. a) Take two glass troughs A and B and fill each one of them two – thirds with soil.
b) In troughs A plant a tiny seedling. In trough B plants a similar seedling and places a clay pot inside the soil.
c) Water the soil in trough A daily and uniformly. Do not water the soil in trough B but put some water in clay pot and leave both the trough for a few days.
d) Now, dig up the seedling carefully form both the troughs without damaging their roots. Observation – Roots of seedling in trough in A is straight. The root of seedling in trough B is bent to the right side i.e., toward the clay pot containing water
6. Draw the structure of a neuron and explain its function.
Ans. Neuron acquires particular information through dendrite located on its cell body. This information is then passed on to the axon. Finally, axon ending passes the information into next neuron at the synapse. As soon as the impulse reaches the dendrite, an electrical impulse is generated due to certain chemical changes in neuron. When the impulse reaches axon ending some chemicals released which pass on the impulse to next neuron. These chemicals are known as neurotransmitters.
7.What are phytohormones? Name them.
Ans. Phytohormones are special chemical compounds released by different parts of plant. They help to co – ordinate growth, development and responses to the environment. They are synthesized at site away from where they act and simple diffuse to the area of action. These are –
a) Auxin
b) Gibberlins
c) Cytokinin
d) Abscisic acid
e) Ethylene.
9. What is the role of the brain in reflex action?
Ans. A reflex action is one which we perform automatically. The sensory and motor nerves meet at a point in the spinal cord on their way to the brain. Thus the information through sensory nerves goes to the brain, where thinking process occurs. But if the reflex action is instant where thinking in not involved then the brain has no role.
10. Which types of glands in human body secrete hormones? State any one location for them.
Ans. There are three types of glands which secrete hormone in human body-
a) Exocrine gland – these are duct glands which do not secrete their secretion into the blood.
For ex – salivary gland. it secretes salivary amylase which digest starch.
b) Endocrine – gland – These are ductless gland, and they pour their secretion in blood. For ex – Pituitary gland. It is master gland, controls most of the activities.
c) Heterocrine gland – which act as both endocrine and exocrine type of glands. For Ex Pancreas – Endocrine part produces hormone insulin and glycogen and exocrine part produce digestive enzymes
11.What are the major parts of the brain? Mention the functions of different parts.
Ans. The brain is covered by a three layered system of membranes; called meninges. Cerebrospinal fluid is filled between the meninges. The CSF provides cushion to the brain against mechanical shocks. The brain is located inside the skull for maximum protection. The human brain can be divided into three regions, viz. forebrain, midbrain and hindbrain.
Some main structures of the human brain are explained below.
Cerebrum: The cerebrum is the largest part in the human brain. It is divided into two hemispheres; called cerebral hemispheres.
Functions of cerebrum:
The cerebrum controls the voluntary motor actions.
It is the site of sensory perceptions; like tactile and auditory perceptions.
It is the seat of learning and memory.
Hypothalamus:
The hypothalamus lies at the base of the cerebrum. It controls sleep and wake cycle (circadian rhythm) of the body. It also controls the urges for eating and drinking.
Cerebellum: Cerebellum lies below the cerebrum and at the back of the whole structure. It coordinates the motor functions. When you are riding your bicycle; the perfect coordination
between your pedaling and steering control is achieved by the cerebellum. Medulla: Medulla forms the brain stem; along with the pons. It lies at the base of the brain and continues into the spinal cord. Medulla controls various involuntary functions; like hear beat, respiration, etc.
12.What are reflex actions? Give two examples. Explain a reflex arc.
Ans. The sudden involuntary movement in a voluntary organ; in response to a stimulus; is called reflex action. Examples of reflex action:
(a) Moving your hand away from a hot iron plate
(b) Blinking of eyes
Reflex Arc:
The path of electrical impulse during a reflex action is called reflex arc. A reflex arc is composed of a sensory neuron, spinal cord, motor neuron and muscle. It involves following steps: The sensory neuron picks signals from the stimulus and carries the signals to the spinal cord. Spinal cord process the signals and sends message through the motor neuron. Motor neuron transmits the signals to the effector muscle so that the muscle can take immediate action.
Ans. Functions of Gibberllins –
(i) Stimulate stem elongation.
(ii) Help in breaking seed dormancy.
(iii) Promote flowering in some plants even under unfavorable conditions
(iv) Help in seed germination.
(v) Promote production of male flowers
.
2. What is the function of receptors in our body? What happens when receptors do not work properly?
Ans. The function of receptors is to defect information form the environment. If receptors do not work properly, the information obtained form 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.
3. What happens at the synapse between two neurons?
Ans. The nerve impulse gets transmitted through the synapse by means of chemical signals. When a stimulus acts on the receptor, chemical reaction is set off which produces an impulse in it. This impulse travels form the dendrite of presynaptic neuron to its cell body and then along its axon. At the end of axon of this neuron, the electrical impulse releases tiny amount of a chemical substance crosses the synapse and starts a similar electrical impulse in the dendrite of the next neuron.
4. What is the need for a system of control and co – ordination in an organism?
Ans. a) It evokes an appropriate movement in response to any change in external environment
b) Multicellular organisms have complex body. So it, co – ordinates various organs of body of an organism work together in a proper manner to produce proper reaction to stimulus
5. Pituitary is a master endocrine gland. Justify this statement.
Ans. Pituitary gland is also known as master gland because it controls the activities of most of the gland.
It regulates the secretion of other glands. Like-
a) Growth hormones – Body growth and development of bones
b) Thyroid stimulating hormone – Secretion of hormones form thyroid gland.
c) Adrenocorticotropic hormone – Secretion of hormones form adrenal glands.
d) Follicle stimulating hormone – Stimulating of growth of ovaries and testes
e) Luteinsing hormone – Secretion of hormone from ovaries & testes
f) prolactin – Regulation of function of mammary gland. Hence, most of functions are controlled by pituitary gland so it is called master gland.
6. Draw the structure of neuron and explain its function.
Ans. Neuron has three components –
(i) Cell body
(ii) Dendrites
(iii) Axon
The dendrite picks up the nerve impulse from receptors and then pass the impulses to the cell body and then along the axon. The axon passes the impulse to another neuron through a junction called synapse.
7. How does our body respond when adrenaline is secreted into the blood?
Ans. When adrenaline is secreted into the blood, it prepares our body for action. It speeds up heart beat and breathing, raises blood pressure and allows more glucose to go into the blood to give us a lot of energy quickly to fight or urn away from frightening situation. The blood supply decreases form the skin and digestive system and increase to skeletal muscles. All there conditions help the individual to respond the emergency situation.
8. Where are Pons and medulla oblongata located? Write their functions.
Ans. Pons and medulla Oblongata are located in hind brain. Pons acts as bridge between brain and spinal cord. Medulla oblongata –
a) It is the reflex centre to control activities like salivation, swallowing, vomiting, breathing, coughing, sneezing and heart beat
b) It also controls sleeps, consciousness and activities of cerebrum
9. List the function of testosterone and estrogen. Where are they secreted?
Ans. Testosterone is secreted in males – It is responsible for development of male sex organs and secondary sex characteristics like moustache, beard & voice. Estrogen is secreted in females – it is responsible for development of female sex organs and secondary sex characteristics like mammary gland and uterine growth.
10. Define ‘nerve impulse’. Which structure in a neuron helps to conduct a nerve impulse?
a) Towards the cell body?
b) Away from the cell body?
Ans. Nerve Impulse – It is the passing of information through neurons is in the form of electrical and chemical signals. This is called nerve impulse.
a) Dendrite
b) Axon
13. What are tropic movements? Name the types of tropic movements in plants.
Ans. The bending or movement of a part of plant in response to the external stimulus is called tropism or tropical movement. It is of following types.
(a) Phototropism – It is response to light. It may be towards light (positive) or away from the light (negative).
(b) Geotropism – It is response to gravity – It may be towards stimulus (positive) and away from the stimulus (negative)
(c) Chemotropism - Response to chemicals. It may be positive or negative.
(d) Hydrotropism – Response to water. It may be positive or negative.
14. Name the different lobes of cerebrum.
Ans. Different lobes of cerebrum –
a) Frontal lobe – It is associated with reasoning.
b) Parietal – Perception of general sensation s like pressure, touch and pain.
c) Occipital – Visual perception.
d) Temporal – Important for interpreting sounds and the language we hear and formation of memories.
15. How do auxins promote the growth of tendril around a support?
Ans. 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 form the support, auxins promote growth. So, due to more auxins in it, the side of tendril, away from the support, grow faster and becomes longer than the side which is in contact with the support and makes the tendril curve towards the support.
17. What are the different kinds of neurons?
Ans. Kinds of neurons –
a) Sensory neurons – convey impulses from receptors to the main nervous system.
b) Motor neurons – carry impulses from the main nervous system to an effector.
c) Connecting (Relay) neurons – connect sensory and motor centres.
18. How does chemical co-ordination takes place in animals. Mention their function.
Ans. The chemical co – ordination in animals takes place through hormonal system called endocrine system. Animal hormones are chemical messengers which are directly poured into the blood by the endocrine glands. Thus, a hormone reaches to the cells. The cells have special molecules on their surface to detect these chemical compounds and recognize the information a particular hormone carrying. There the cells act accordingly. The chemical co – ordination is fast as hormones diffuse readily around the cells
20. Nervous and hormonal system together performs the functions of control and co – ordination in human beings. Justify the statement.
Ans. A number of interactions between the environment and the animal are a result of combined action of both neurons and endocrine system for which specialized tissues are used to provide control and co – ordinations activities.
21. What is the difference between a reflex action and walking?
Ans.Reflex action.
a.Take place without thought
b.controlled by spinal cord
c.It is involuntary action
Walking
a.Takes place after thought
b.Controlled by cerebellum.
c.It is a voluntary action.
22. What happens at the synapse between two neurons?
Ans. At synapse, the electrical impulse generated a dendrite of a neuron is passed on to dendrite of another neuron in form of chemical impulses. The chemical present at synapse is called neurotransmier.
23. How do auxins promote the growth of a tendril around a support?
Ans. When tendrils come in contact of any support, the part of the tendril in contact does not grow as rapidly as the part away from the object due to auxin secreted moves away from the object in contact. This rapid growth on one side causes tendril to circle around the object.
24. Design an experiment to demonstrate hydrotropism.
Ans. Take a tin box with hole at bottom. Fill it with moist saw dust. Sow some gram seeds in it. Keep the tin box in tilted position. When seeds start germinating, water the saw dust only in lower side of the tin box. You will observe that the radicle move towards the wet saw dust. This shows that root is positively hydrotropic.
25. How does our body respond when adrenaline is secreted into the blood?
Ans. When adrenaline reaches the various target organ through blood. All these organs respond together to enable our body to deal with situation like running away from scary situation. When adrenaline reaches the heart, it beats faster to supply more oxygen to our muscles. The small arteries around digestive system and skins contracts to divert the blood towards muscles. All these response enable our body to deal with situation.
26. Why are some patients of diabetes treated by giving injections of insulin?
Ans. Diabetes is caused due to non or less secretion of hormone insulin by pancreas. In such person, the blood sugar level is high. Insulin converts extra sugar present in blood into glycogen. Patients suffering from diabetes are given insulin injection to control their blood sugar level.
27. What is the function of receptors in our body? Think of situation where receptors do not work properly. What problems are likely to arise?
Ans. Receptors detect all the information from our environment. These receptors are located in our sense organs. In case any of the receptors do not work properly we will not be able to perceive that particular information.
28. How phototropism does occur in plants?
Ans. Movement of shoot towards light is called phototropism. This movement is caused due to more growth of cells towards the shaded side of the shoot as compared to the side of shoot towards light. More growth of cells is due to secretion of auxin towards the shaded side.
29. Which signals will get disrupted in case of a spinal cord injury?
Ans. (i) Reflex action
(ii) Impulses from various body parts will not conducted to brain.
(iii) Message from brain will not be conducted to various organs.
30. How does chemical coordination occurs in plants?
Ans. Chemical coordination in plants is maintained by plant hormones also known as phytohormones. Some of these hormones promote growth while some inhibit it. Some hormones include auxin, Gibberellins, Cytokinin etc.
31. What is the need for a system of control and coordination in an organism?
Ans. An organism has different organs which perform various factions. The survival of an organism depends on integrated and coordinated functions of these organs. Nervous and endocrine system of an organism makes them work together like parts of one machine to accomplish homeostasis or coordination.
32. How are involuntary actions and reflex actions different from each other?
Ans. Difference between involuntary and reflex actions is as follows Involuntary Actions:It is a set of muscles movement over which we do not have control.Such actions are controlled by brain.For example contraction of muscle of our digestive tract,beating of heart etc.
Reflex Action:It is rapid, spontaneous and involuntary activity that is produced in response to a stimulus.It is controlled by spinal cord.Example-removal of hand with jerk when someone touches a hot object.
33. Compare and contrast nervous system and hormonal control and coordination in animals.
Ans. Nervous control
a.Consists of nerve impulses conducted by neurons from one organ to another organ.
b.Nervous impulses produce rapid short lasting responses.
c.Nervous impulses are not specific in their action
Hormonal control
a.It consists of endocrine system which secretes chemical messengers hormones secreted directly in blood
b.Hormones produce longer lasting reponses
c.Action of hormones is highly specific
35. On touching a hot plate, you suddenly withdraw your hand. Which category of neurons became active first and which one next?
Ans. On touching a hot plate, first the sensory neurons are activated, which take the information to the brain or the spinal cord. Next, the motor neurons become active and bring the impulses from the brain to the muscles. In receiving these impulses, the muscles contract, and the hand is immediately removed from the hot plate.
36. How does the plant shoot bends, when the plant is placed in a room having only one open window?
Ans. When the plant is placed in such a room that has only one open window, the shoot of the plant bends towards the direction of light. Plant hormone axing is formed that diffuses towards the shady side of the shoot and stimulates the cells to live longer on the side of the shoot which is away from light. In this way the shoot bends towards the light.
37. Give a reason to explain why
(a) adrenaline helps in dealing emergency situations?
(b) secretions of growth hormone should be specific in the human body?
Ans. a. 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 is further diverted to skeletal muscles. All these responses together prepare the body to deal with the emergency situations.
b. If growth hormones is secreted in excess during childhood then it leads to gigantism while the less secretion of this hormone during childhood causes dwarfism.
38. A man becomes unconscious due to head injury. A pin is pricked on his foot, he withdraws his foot. Why? Explain.
Ans. It is reflex action. Stimulus is perceived by receptor (skin). Sensory nerve sends the sensation from receptor to the spinal cord. Then spinal cord sends the message through motor nerves to the effectors. Effectors i.e. muscles help in withdrawing his foot.
2. Mention one function for each of these hormones.
i) Thyroxine
ii) Insulin
iii) Adrenaline
iv) Growth hormone
v) Testosterone.
Ans. (i) Thyroxin – Control overall metabolic rate of the body (carbohydrate, protein and fat metabolism)
(ii) Insulin – Conversion of glucose to glycogen in liver and muscles, thus decreases blood glucose level.
(iii) Adrenalin – increases heart beat, blood pressure and blood glucose level.
(iv) Growth hormone – Body growth and development of bones.
(v) Testosterone – Development of male sex organ sand secondary sex characteristics like moustache, beard & voice.
3. a) what are hormones?
b) list four characteristics of hormones
Ans. Hormones are chemical substances which are secreted in very less amount by specialized tissues called endocrine glands. Characteristics of hormones are –
1) They are required in very less amount.
2) Hormones are specific in their function.
3) They act away from the site of production.
4) Deficiency or over secretions of hormones have negative effects in the body.
4. Design an experiment to demonstrate hydrotropism.
Ans. a) Take two glass troughs A and B and fill each one of them two – thirds with soil.
b) In troughs A plant a tiny seedling. In trough B plants a similar seedling and places a clay pot inside the soil.
c) Water the soil in trough A daily and uniformly. Do not water the soil in trough B but put some water in clay pot and leave both the trough for a few days.
d) Now, dig up the seedling carefully form both the troughs without damaging their roots. Observation – Roots of seedling in trough in A is straight. The root of seedling in trough B is bent to the right side i.e., toward the clay pot containing water
6. Draw the structure of a neuron and explain its function.
Ans. Neuron acquires particular information through dendrite located on its cell body. This information is then passed on to the axon. Finally, axon ending passes the information into next neuron at the synapse. As soon as the impulse reaches the dendrite, an electrical impulse is generated due to certain chemical changes in neuron. When the impulse reaches axon ending some chemicals released which pass on the impulse to next neuron. These chemicals are known as neurotransmitters.
7.What are phytohormones? Name them.
Ans. Phytohormones are special chemical compounds released by different parts of plant. They help to co – ordinate growth, development and responses to the environment. They are synthesized at site away from where they act and simple diffuse to the area of action. These are –
a) Auxin
b) Gibberlins
c) Cytokinin
d) Abscisic acid
e) Ethylene.
9. What is the role of the brain in reflex action?
Ans. A reflex action is one which we perform automatically. The sensory and motor nerves meet at a point in the spinal cord on their way to the brain. Thus the information through sensory nerves goes to the brain, where thinking process occurs. But if the reflex action is instant where thinking in not involved then the brain has no role.
10. Which types of glands in human body secrete hormones? State any one location for them.
Ans. There are three types of glands which secrete hormone in human body-
a) Exocrine gland – these are duct glands which do not secrete their secretion into the blood.
For ex – salivary gland. it secretes salivary amylase which digest starch.
b) Endocrine – gland – These are ductless gland, and they pour their secretion in blood. For ex – Pituitary gland. It is master gland, controls most of the activities.
c) Heterocrine gland – which act as both endocrine and exocrine type of glands. For Ex Pancreas – Endocrine part produces hormone insulin and glycogen and exocrine part produce digestive enzymes
11.What are the major parts of the brain? Mention the functions of different parts.
Ans. The brain is covered by a three layered system of membranes; called meninges. Cerebrospinal fluid is filled between the meninges. The CSF provides cushion to the brain against mechanical shocks. The brain is located inside the skull for maximum protection. The human brain can be divided into three regions, viz. forebrain, midbrain and hindbrain.
Some main structures of the human brain are explained below.
Cerebrum: The cerebrum is the largest part in the human brain. It is divided into two hemispheres; called cerebral hemispheres.
Functions of cerebrum:
The cerebrum controls the voluntary motor actions.
It is the site of sensory perceptions; like tactile and auditory perceptions.
It is the seat of learning and memory.
Hypothalamus:
The hypothalamus lies at the base of the cerebrum. It controls sleep and wake cycle (circadian rhythm) of the body. It also controls the urges for eating and drinking.
Cerebellum: Cerebellum lies below the cerebrum and at the back of the whole structure. It coordinates the motor functions. When you are riding your bicycle; the perfect coordination
between your pedaling and steering control is achieved by the cerebellum. Medulla: Medulla forms the brain stem; along with the pons. It lies at the base of the brain and continues into the spinal cord. Medulla controls various involuntary functions; like hear beat, respiration, etc.
12.What are reflex actions? Give two examples. Explain a reflex arc.
Ans. The sudden involuntary movement in a voluntary organ; in response to a stimulus; is called reflex action. Examples of reflex action:
(a) Moving your hand away from a hot iron plate
(b) Blinking of eyes
Reflex Arc:
The path of electrical impulse during a reflex action is called reflex arc. A reflex arc is composed of a sensory neuron, spinal cord, motor neuron and muscle. It involves following steps: The sensory neuron picks signals from the stimulus and carries the signals to the spinal cord. Spinal cord process the signals and sends message through the motor neuron. Motor neuron transmits the signals to the effector muscle so that the muscle can take immediate action.
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