Main Functions:
(A) Fore-brain: (i) It has regions which receives sensory impulses from various receptors. Based upon information and information stored in the brain, it make a decision how to respond. The information is passed on to motor areas which control movement of voluntary muscles such as our leg muscles.
(ii) It is the site of intelligence and judgement.
(iii) It controls intellect, speech, language, hunger and the spinal senses.
(B) Mid-brain:
(i) It controls the reflex action of right, such as change in the size of pupil, hearing and of balance. Thus, it controls such involuntary action.
(C) Hind-brain:
(i) It controls involuntary actions such as blood pressure, salvation, and vomitting.
(ii) It regulates the voluntary movement of skeletal muscles (motor activities) to maintain the posture and balance of the body. This controlled cerebellum, a part hind-brain. It controls activities such as walking in a straight line, riding a bicycle, picking up a pencil etc.
(iii) Medulla oblongata controls life activities such as respiration and circulation.
Nervous system |
Hormonal system |
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1. |
The nervous system controls the various functions by the units called neurons. |
1. |
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. |
2. |
Hormones are directly poured into blood. Later on they diffuse to body cells, and also cell to cell. |
(b) Motor nerves which carry the response message to muscles or glands. |
They are synthesised at a places away from where they act and simple diffuse to the area of action. |
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3. |
Nervous system has a network of nerves spread through out the body. |
3. |
Hormonal system does not has such a network. |
4. |
(a) Dendrites of a neuron acquire information. |
4. |
Cells have special molecules on their surface to recognise information carried by hormones to act up accordingly. |
(b) Information travels as an electric impulse through cell body and axon. |
Hormones are not conducted through electrical impulses. |
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(c) The impulse is converted into a chemical signals for onward transmission. |
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5. |
Nervous system does not use feedback mechanism in generating electrical impulse or producing neurochemical transmitter (especially at synapsis). |
5. |
The timing and amount of hormone released are regulated by feedback mechanisms. |
6. |
In nervous system, electrical impulses are generated for quick transmission of information. But there are limitation— (i) impulses will reach only those cells that connect by nervous tissue. |
6. |
Hormones are chemical messenger that diffuse to a cells 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. |
(ii) Once an electrical impulse is generated in a cell and transmitted, the cell takes some time to generate another impulse. That is cells cannot continuously create and transmit electrical impulses. |
Hormones can reach all cells of the body (through blood in animals), regardless of nervous connections and it can be done steadily and persistently. |
Voluntary actions |
Involuntary/Reflex actions |
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1. |
The actions are under the will or conscious of the individual. |
1. |
Actions occur without consulting the will. |
2. |
They may or may not involve information from receptors or sense organs. |
2. |
Involuntary actions always occur in response to stimuli picked up by receptors. |
3. |
Impulses originate in the brain. |
3. |
Impulses originate in the region of receptors. |
4. |
Every voluntary action occurs under conscious directions from brain. |
4. |
Brain is seldom consulted consciously though an involuntary action always involves spinal cord or brain for transfer of information from afferent neurons to efferent neurons. |
5. |
The actions employ voluntary muscles. |
5. |
The actions employ involuntary muscles but occasionally voluntary muscles also get involved. |
6. |
Voluntary actions do not occur in the form of an arc. Mainly three parts are involved— brain (CNS), efferent neuron and effector organ. |
6. |
They occur in the form of a reflex arc. A reflex arc consists of five parts—receptors, afferent neuron, interneuron in CNS, efferent neuron and effector organ. |
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 of our nervous system.
When nerve impulse reaches the muscle cells move by changing their shape. Special proteins cause both change in shape and their arrangement in the cell in response to nervous electrical impulses.