Which signals will get disrupted in case of a spinal cord injury?
In case of spinal cord injury the following sihnals will be disrupted:
(i) Reflex actions will be disturbed because reflex arcs are located in the spinal cord. So, the quick responses needed to safe guard the body will not take place. The delayed responses may pose harm to the body. For example, delayed response to touching a hot object may cause burn of the body part.
(ii) Impulses from various body parts will not be communicated to brain.
(iii) Messages from brain to body parts will not be communicated.
What is the need for a system of control and coordination in an organism?
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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. |
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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. |
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(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. |
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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. |
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(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. |
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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. |
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(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. |
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Involuntary action |
Reflex action |
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1. |
The actions which we cannot do by thinking about them even if we wanted to. For example, beating of heart. |
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An action i.e., response which is immediate (spontaneous) and that does not need processing by the brain is called reflex action. For example, immediate removal of hand on touching a hot plate. |
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2. |
Involuntary actions are controlled by brain. |
2. |
Reflex actions are controlled by spinal cord. |
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