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प्रश्न
Explain the mechanism of reflex action with the help of a suitable diagram.
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उत्तर
Mechanism of Reflex action : The reflex action is completed in a series of events. The events that occur are,
(1) Pricking of needle stimulates skin receptors by receiving stimulus,
(2) Sensory impulse is formed and it is carried by denderites innervating the skin.
(3) Impulse is carried to the association neuron by axon of sensory neuron,
(4) When impulse reaches the end of the axon there is a synapse.
(5) Synaptic transmission is chemical: The synaptic buttons at the end of the axon releases a neurotransmitter substance acetylcholine. It fills the synaptic gap and helps in chemical transmission of the impulse from axon of one neuron to dendron of the other neuron. Once the impulse reaches the dendrites of association neuron, axonic buttons release an enzyme acetylcholine estrase which neutralizes the acetycholine and again a synaptic gap is formed. This mechanism helps to receive new impulse or avoid the mixing of different impules.
(6) The association neuron receive sensory impulse, interprets it, analyses it and generates motor impulse.
(7) Motor impulse again travels through synapse between association neuron and motor neuron.
(8) Impulse travels through motor neuron and reaches effector organ like skeletal muscles or the gland.
(9) The effector organ gives a proper response like contraction of the muscles or secretion by the gland.
For e.g., when the hand is pricked with a needle, immediately hand is withdrawn from the source.
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संबंधित प्रश्न
The diagram given below shows the internal structure of a spinal cord depicting a phenomenon. Study the diagram and answer the questions:
1) Name the phenomenon that is depicted in the diagram. Define the phenomenon.
2) Give the technical term for the point of contact between the two nerve cells.
3) Name the parts numbered 1, 2 and 3.
4) How does the arrangement of neurons in the spinal cord differ from that of the brain?
5) Mention two ways by which the spinal cord is protected in our body.
Name two parts of the body which contain receptors of chemical stimuli.
Our ______ system allows us to react to our surroundings. Information from receptors passes along ______ neurons to our brain. Our brain sends impulses along ______ neurons to our muscles.
What are the various sense organs in our body?
What is a reflex action? Explain with the help of an example.
Which of the following statements is correct about receptors?
P is a cell (or group of cells) in the human body which is sensitive to a particular type of stimulus and conveys the messages to CNS through nerves Q. On the other hand, R is a part of the human body which can respond to a stimulus according to the instructions sent from the CNS through nerves S.
(a) What is P? Name five organs which contain cells (or group of cells) like P.
(b) Name the nerves Q.
(c) What is R? Give two examples of R.
(d) Name nerves S.
(e) How do messages travel through the nerves Q and S?
Reflex action is controlled by the
Explain the following term :
Conditioned reflex
State whether the following is
Constriction of pupil
