Control and Coordination
NCERT Solutions
NCERT Exercise
1. Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
(d) cytokinin
2. The gap between two neurons is called a
(a) Dendrite.
(b) Synapse.
(c) Axon.
(d) Impulse
(b) Synapse
3. The brain is responsible for
(a) Thinking.
(b) Regulating the heartbeat.
(c) Balancing the body.
(d) all of the above
(d) all 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?
Receptors are present in all parts of our body skin, eye, nose, tongue etc. Receptors detect signal and send it to brain in the form of electrical signals. If these receptors are damaged then it they will not detect the input which leads to the harm for our body in dangerous situation.
5. Draw the structure of a neuron and explain its function.
Our brain, spinal cord, and nerves are composed of nervous tissue. The cells of nervous tissue are called Nerve cells or Neurons.
Structure of neuron
- Cell body- It consists of cytoplasm and a nucleus.
- Dendrite- From the cell body, short thin hair-like parts arise in the form of branches. These are called dendrites. They help in detecting the information from the environment.
- Axon- A long cylindrical structure emerging from the cell body. The information detected by the dendrites travels through the axon and reaches the next nerve and finally to the brain.
- Nerve ending- The ending of the axon is branched, and they help in neurotransmission.
6. How does phototropism occur in plants?
Phototropism is the movement of plants or other organisms in response to light. It is a directional movement. The movement can be either towards the light (positive phototropism) or away from (negative phototropism) it. Shoot of the plant shows positive phototropism and root shows negative phototropism. Bending of shoot towards the light is due to the action of hormone auxin. When plant gets sunlight, Auxin is distributed uniformly. If plant is getting sunlight only from one side then the auxin spread to the part which do not receive sunlight. Cells grow more in areas of the plant where auxins are highly concentrated. So that the plant parts in the shady region grow faster and bends towards the light.
7. Which signals will get disrupted in case of a spinal cord injury?
Signals coming from the nerves as well as the signals coming to the receptors will be disrupted.
8. How does chemical coordination occur in plants?
Chemical coordination in plants happens with the help of phytohormone. Phytohormones are responsible to regulate growth, development, reproductive processes, longevity, and death of plants. The five types of phytohormone are auxins, gibberellins, cytokinin, abscisic acid, and ethylene.
9. What is the need for a system of control and coordination in an organism?
Control and coordination are required for an organism
(i) To save the body of the organisms from the harmful changes in the environment.
(ii) To control the speed of voluntary and involuntary actions.
(iii) To have the capability to think and learn for responding to any stimuli.
10. How are involuntary actions and reflex actions different from each other?
11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Intext Exercise
Pg. No. 119
1. What is the difference between a reflex action and walking?
Reflex action is an involuntary action. This action is a fast and automatic response to the stimuli. Reflex action is controlled by spinal cord.
Walking is a voluntary action. Walking activity is controlled by brain.
2. What happens at the synapse between two neurons?
Synapse a gap between two neurons. The electric signal is now converted to chemical signal, fill the gaps between neurons and passes to next neuron. There it is converted back to electrical signal.
3. Which part of the brain maintains posture and equilibrium of the body?
Cerebellum
4. How do we detect the smell of an agarbatti (incense stick)?
Smell of an agarbatti is detected by olfactory receptors present in the nose. Now the receptors produce chemical reactions which generate electrical impulses. These electrical impulses are carried by sensory neurons to sensory area of forebrain. Forebrain interprets this signal.
5. What is the role of the brain in reflex action?
Reflex action takes place in the spinal cord. Only the infomation regarding this reflex action goes to the brain. This will help one to to get awareness of the stimulus and prevent himself from that situation again.
Pg. No. 122
1. What are plant hormones?
Plant hormones are organic substance which are produced in plants. These hormones are moved from one part to another part of plant. They help to coordinate growth, development and responses to the environment. Ex: Auxin’s Gibberlin’s, cytokines, abscisic acid and ethylene.
2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
3. Give an example of a plant hormone that promotes growth
Auxin and gibberellin
4. How do auxins promote the growth of a tendril around a support?
When a tendril comes in contact with a support, the auxin present in the tip moves away from the support and promotes the growth in the place away from support. So that tendril away from the support grows faster and the tendril bends towards the support.
5. Design an experiment to demonstrate hydrotropism.
Hydrotropism is the growth movement of plant towards water.
Experiment to show hydrotropism in plants :
1. Plant a seedling in a vessel containing soil
2. Adjacent to the seedling put a porous pot containing water.
3. Leave the set up for few days.
4. On examining the roots of seedlings it is observed that the roots bend towards the source of water and do not grow straight.
Result : It confirms that plant shows hydrotropism as the roots bend towards the porous pot of water.
Pg. No. 125
1. How does chemical coordination take place in animals?
Chemical coordination takes place in animals with the help of hormone. Hormones regulate the growth, development and homeostasis of the animals.
2. Why is the use of iodized salt advisable?
The deficiency of iodine can be sort out by using iodine salt. Deficiency of iodine cause goiter. The release of thyroxine from the thyroid gland will be decreased as a result of deficiency of iodine. This affects fat, carbohydrate and protein metabolism.
3. How does our body respond when adrenaline is secreted into the blood?
Adrenaline is a hormone secreted when a person is frightened or mentally disturbed. It will increase the heart beat and blood supply to the muscles. It increases the breathing rate. It also increases blood pressure and allows entry of more glucose into blood.
4. Why are some patients of diabetes treated by giving injections of insulin?
Insulin regulates blood glucose level of diabetes patients.