"AKC SCIENCE CLASSES"
CLASS 10 TH (CBSE AND MP BOARD)
CHAPTER 07
CONTROL AND COORDINATION
EXERCISE QUESTIONS AND ANSWERS
Q.01:- Which of the following is the plant hormone ?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Ans:- (d) Cytokinin
Q.02:- The gap between two neurons is called a
(a) Dendrite
(b) Synapse
(c) Axon
(d) Impulse
Ans:- (b) Synapse
Q.03:- The brain responsible for
(a) thinking
(b) regulating the heart beat
(c) balancing the body
(d) all of the above.
Ans:- (d) all of the above
Q.04:- 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:- Function of receptors :- Receptors are the specialised tips of some nerves. They are usually located in our sense organs like the nose, the inner ear, the tongue, etc.
The function of receptors is to detect information from the environment.
For example, gustatory receptors detect taste while olfactoreceptors detect smell.
If receptors do not work properly, the information obtained from the environment will be delayed to reach the spinal cord or brain. In this situation, the response to the environmental stimulus is delayed causing harm to the body.
For example, touching a hot object is an urgent and dangerous situation. If receptors are not present in the nerves of touching sense organ, the response may be delayed and we may get burnt.
Q.05:- Graw the structure of a neuron and explain its function.
Ans:- Diagram of a neuron
(b) State the objective of the experiment for which experiment set up is shown in the given diagram.
(b) Objective of the experiment set up is to show 'Response of the plant to the direction of light'.
Q.07:- Which signals will get disrupted in case of a spinal cord injury?
Ans:- (ⅰ) Reflex actions will be disturbed because reflex arc are located in the spinal cord. So, the quick responses needed to safe guard the body will not take place. The delayed responses may cause harm to the body. For example, delayed response to touching a hot object may cause burn of the body part. When a bright light is focussed on our eyes, the eyes' pupils contract to allow only sufficient light to the retina. This is a spontaneous reflex action to prevent damage to the retina of eyes by bright light.
(ⅱ) Impulses form various body parts will not be communicated to brain.
(ⅲ) Messages from brain to body parts will not be communicated.
Q.08:- How does chemical coordination occur in plants?
Ans:- Different plant hormones help to coordinate growth, development and response to the environment. They are synthesised at places away from where they act and simply diffuse to the area of action. For example, when growing plants detect light a hormone called auxin, synthesised at the shoot tip. Auxin diffuses to other cells and helps the cells to grow longer.
Q.09:- What is the need for a system of control and coordination in an organism ?
Ans:- Living things show different types of movements. These movements may be due to growth, in response to change in environment or to procure food. Each kind of a change in the environment evokes an appropriate movement in response. For example, a cat must run faster than the rat to catch it. Thus, control over movements is response of environment is necessary. Moreover, movements made by different parts of the multicellular body must be coordinated. We need coordination of figures and thumb to hold a pen. So, multicellular organisms need specialised tissues to provide control and coordination.
Q.10:- How are involuntary action and reflex actions different from each other?
Ans:-
| SL No. | Involuntary action | Reflex actions |
|---|---|---|
| 1 | Involuntary actions takes place without the conscious choice of an organism. | Reflex actions are those actions takes place along with stimuli. |
| 2 | These actions are controlled by the medulla oblongata or the mid brain. | These actions are controlled by spinal cord. |
| 3 | The speed is relatively slower. | The speed is very quick. |
| 4 | Example is beating of heart. | Example is blinking of eyes. |
Q.11:- Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Ans:-
| SL No. | Nervous System | Hormonal System |
|---|---|---|
| 1 | The nervous system controls the various functions by the units called neurons. | Hormones are chemical messangers secreted by endocrine (ductless) glands. |
| 2 | Neurons form two types of nerves :- (a) Sensory nerves which receive the information to convey to brain or spinal cord. (b) Motor nerves which carry the response message to muscles or glands. | Hormones are directly poured into blood. Later on they diffuse to body cells, and also cell to cell. They are synthesised at places away from where they act and simply diffuse to the area of action. |
| 3 | Nervous system has a network of nerves spread through out the body. | Hormonal system does not has such a network. |
| 4 | (a) Dendrites of a neuron acquire information. (b) Information travels as an electric impulse through cell body and axon. (c) The impulse is converted into a chemical signals for onward transmission. | Cells have special molecules on their surface to recognise information carried by hormones to act up accordingly. Hormones are not conducted through electrical impulses. |
| 5 | The nervous system gets information from our sense organs and act through our muscles to meet out. | Hormones help in growth and development of the body, controlling body metabolism, development secondary characters etc. |
| 6 | Nervous system is does not use feedback mechanisms in generating electrical impulse or producing neurochemical transmitter (especially at synapsis). | The timing and amount of hormone released are regulated by feedback mechanisms. |
| 7 | In nervous system, electrical impulses are generated for quick transmission of information. But there are limitations :-
| Hormones are chemical messengers that diffuse to a cell of the body. The body cells, using special molecules on their surfaces, recognise information and even transmit it. Hormones are synthesised at places away from where they act. Hormones can reach all cells of the body (through blood in animals), regardless of nervous connections and it can be done steadily and persistently. |
Q.12:- What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Ans:- Movement in sensitive plant :- The movement in sensitive plant leaves takes place in response to touch (shock) stimulus. When terminal pinnule is touched, the stimulus is conducted to its base and the pinnules droop down. This happens in charge in osmotic pressure (decrease) causing shrinkage. When the stimulus time is over, osmotic pressure increases and the cells swell, the pennules become normal. This is an example of growth independent movement.
Thus, movement happens at a point different from the point of touch (stimulus). So, the information that a touch has occurred communicated through electrical-chemical means from cell to cell, but not through specialised tissues. Plant cells change in shape by changing amount of water in them, resulting in swelling or shrinking, during movement.
Movement in our legs :- Our legs are provided with nerves which have connection with muscles. To lift the leg, the brain passes information to nerves.
The information travels as an electrical impulse. On reaching leg muscles, impulse is converted into a chemical signal and the muscles contract to lift the leg. Movement of legs takes place due to muscle contraction and relaxation, which is under the control our nervous system.
When nerve impulse reaches the muscle cells the cells moves by changing their shape. Special proteins cause both changes in shape and their arrangement in the cell in response to nervous electrical impulses.
