Control and coordination
In text questions
Page no. 119
1. What is the difference between a reflex action and walking?
Ans:
In text questions
Page no. 119
1. What is the difference between a reflex action and walking?
Ans:
- Reflex action is involuntary action which means it is not under control of brain only involves spinal cord, it is rapid, thus gives instant response to the stimulus and not affected by our thinking.
- But walking is a voluntary action controlled by brain involves central nervous system and spinal cord both and affected by our thinking.
2. What happens at the synapse between two neurons?
Ans: A very small gap that occurs between the last portion of axon of one neuron and the dendron of the other neuron is known as a synapse. It acts as a one way valve to transmit impulsee in one direction only. This uni-direction transfer of impulses occurs as the chemicals or neurotransmitters are produces in only one side of neuron i.e. the axon's side. from axon the impulses travel across the synapse to the dendron of the other neuron.
3. Which part of the brain maintains posture and equilibrium of the body?
Ans: Cerebellum
4. How do we detect the smell of an agarbatti (incense stick)?
Ans: The thinking part of our brain is the forebrain. It has separate area that are specialized for hearing,smelling,sight,taste,touch,etc. The forebrain also has regions that collect informations or impulse from the various sensory receptors. When the smell of an incense stick reaches us. our olfactory receptors detect it. Then, the forebrain interprets it by putting it together with the information received from other receptors and also with the information already stored in the brain as memory.
5. What is the role of the brain in reflex action?
Ans: Reflex action occurs in spinal cord. The brain and spinal cord constitute the central nervous system. They receive information from all parts of the body and integrate it.
Page no.122
1. What are plant hormones?
Ans: The chemical substances produced in plants which control growth, development and responses in plants, are called plants plant hormones.
For example: Auxins, Gibberellins, Cytokinins and abscisic acid.
2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Ans:
3. Give an example of a plant hormone that promotes growth.
Ans: Auxin
4. How do auxins promote the growth of a tendril around a support?
Ans: Auxin is a plant growth hormone. When the tip of the tendril touches a support, then the auxins present on its tip moves to the side of tip which is away from the support, so due to more auxins in its tendrils away from the support grows faster,
5. Design an experiment to demonstrate hydrotropism.
Ans: Hydro means water hydrotropism means growth towards water.
Materials required: Seed, A big container, porous water pot, water and sand.
Procedure:
- The tray should be big enough to accommodate the porous pot.
- Fill the tray with sand and insert some seeds in it.
- Make a pit in the sand and insert the porous pot in it.
- Fill the porous pot with water. Leave the set up for about a week.
Observation:
After a week when seeds are taken out it is observed that roots grow in the direction of the porous pot. This shows hydrotropic movement in roots.
Page no. 125
1. How does chemical coordination take place in animals?
Ans: Chemical coordination takes place in animals with the help of hormones. Hormones are the chemical fluids that are secreted by the glands of the endocrine system. Hormones regulate the overall growth and development of the animals.
2. Why is the use of iodised salt adviable?
Ans: Iodine is necessary for the thyroid gland to make thyroxin hormone. Thyroxin regulates carbohydrate, protein and fat, metabolism in the body so as to provide the best balance for growth iodine is essential for the synthesis of thyroxin. In case iodine is deficient in our diet, their is a possibility that we might suffer from goiter. One of the symptoms in this disease is a swollen neck.
3.How does our body respond when adrenaline is secreted into the blood?
Ans:When someone is in danger or in emergency then adrenal gland secrete adrenaline hormone. It is secreted directly into the blood and is transported to different parts of the body. It speeds up the heartbeat and hence supplies more oxygen to the muscles.
4. Why are some patients of diabetes treated by giving injection of insulin?
Ans:Diabetes patients as a treatment, they might be taking injection of insulin. This is a hormone which is produced by the pancreas and helps in regulating blood sugar levels. If it is not secreted in proper amounts, the sugar level in the blood rises causing many harmful effects.
Page no. 125
Page no. 125
Exercise
1. Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Ans: Cytokinin
2. The gap between two neurons is called a
(a) dendrite
(b) synapse
(c) axon
(d) impulse
Ans: Synapse
3. The brain is responsible for
(a) thinking
(b) regulating the heart beat.
(c) balancing the body
(d) all of the above
Ans:all of the above
4. What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
Ans:All information from our environment is detected by the specialised tips of some nerve cells. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell. We detect that we are touching a hot object by the action of receptors present on varous organs or tissues. If olfactory receptor not works properly then we are not able to smell thing like aggarbatti, perfumes, flavour of food.
5.Draw the stucture of a neuron and explain its function.
Ans: Neuron are nerve cells which are the functional units of the nervous system. The three main parts of a neuron are dentrite,cell body and axon.
Dendrite: It detect information and conducts the messages towards the cell body.
Cell body: It contains nucleus, mitochondria, and other cell organelles. It maintains the growth of the cell.
Axon: It conducts messages away from the cell body and pass to the next neuron.
6. How does phototropism occur in plants?
Ans: Photo means light. The response of plant towards the environmental triggers, light which change the directions that plant parts grow in is called phototropism.The directional, or tropic, movements can be either towards the light, or away from it. So, in two different kinds of phototropic movement, shoots respond by bending towards light while roots respond by bending away from it.
For eg. Sunlight bends towards the sun from where the light is coming. This is the response of sunflower towards the plants.
7. Which signals will get disrupted in case of a spinal cord injury?
Ans: Reflex actions are involuntary actions and controlled by the spinal cord thus, gets disrupted in case of spinal cord injury.
8. How does chemical coordination occur in plants?
Ans: Chemical coordination occurs in plants with the help of fluids secreted in plants known as phytohormones or plant hormones. These hormones regulate the growth of the plants. For example auxin is responsible for the growth of the plants and cytokinin helps in cell division in the fast growing part of the plant such as plant hormones.
9. What is the need for a system of control and coordination in an organism?
Ans: There are various organs and organ systems in a complex organism. These organ systems must be carefully controlled and coordinated for healthy survival of the organism. A lack of coordination between these systems can cause lot of troubles for the organism. In the body of an organism various fluids are secreted from the glands of the endocrine system. These hormones are responsible for the overall growth and development of an organism. All other daily decisions that include voluntary and involuntary action are controlled by central nervous system (CNS).
10. How are involuntary actions and reflex actions different from each other?
Ans: Involuntary actions are not controlled by us they are independent process means there is no stimulus involved in these actions but reflex action is also involuntary in nature but they involves stimulus means functions or respond according to it.
For example: Involuntary actions: Heart beat, breathing process, etc.
Reflex actions: stepping out in bright light, changes in size of pupil of eyes.
11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Ans:
For eg. Sunlight bends towards the sun from where the light is coming. This is the response of sunflower towards the plants.
7. Which signals will get disrupted in case of a spinal cord injury?
Ans: Reflex actions are involuntary actions and controlled by the spinal cord thus, gets disrupted in case of spinal cord injury.
8. How does chemical coordination occur in plants?
Ans: Chemical coordination occurs in plants with the help of fluids secreted in plants known as phytohormones or plant hormones. These hormones regulate the growth of the plants. For example auxin is responsible for the growth of the plants and cytokinin helps in cell division in the fast growing part of the plant such as plant hormones.
9. What is the need for a system of control and coordination in an organism?
Ans: There are various organs and organ systems in a complex organism. These organ systems must be carefully controlled and coordinated for healthy survival of the organism. A lack of coordination between these systems can cause lot of troubles for the organism. In the body of an organism various fluids are secreted from the glands of the endocrine system. These hormones are responsible for the overall growth and development of an organism. All other daily decisions that include voluntary and involuntary action are controlled by central nervous system (CNS).
10. How are involuntary actions and reflex actions different from each other?
Ans: Involuntary actions are not controlled by us they are independent process means there is no stimulus involved in these actions but reflex action is also involuntary in nature but they involves stimulus means functions or respond according to it.
For example: Involuntary actions: Heart beat, breathing process, etc.
Reflex actions: stepping out in bright light, changes in size of pupil of eyes.
11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Ans:
12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Ans: The movement of sensitive plants leaves takes place due to the sudden loss of water in the pad-like swelling at the base of all the leaves. pulvini limp gets drooped and folded due to the loss of water. On the other hand, the movement of our legs take place due to the muscles of legs on the leg bones.
