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Question
(a) What is a neuron? Draw a labelled diagram of a neuron.
(b) What is a synapse? What happens at the synapse between two neurons? How are the messages carried across a synapse? Explain with the help of a labelled diagram.
(b) What is a synapse? What happens at the synapse between two neurons? How are the messages carried across a synapse? Explain with the help of a labelled diagram.
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Solution
(a) A neuron is a structural and functional unit of the nervous system. A neuron or nerve cell has three components: the cell body, the dendrites and the axon.
Diagram of a neuron:
(b) Synapses are microscopic gaps present in between pairs of adjacent neurons over which nerve impulses pass from one neuron to the next.
A nerve impulse, on reaching the terminal end of an axon, releases chemicals called neurotransmitters at its tip. These chemicals cross the synapse and start the impulse in the next neuron or to an effector organ.
A receptor in a sense organ is in touch with the dendrites of the sensory neuron. When a stimulus acts on the receptor, a chemical reaction is initiated that produces an electrical impulse in the receptor. This impulse travels from the dendrites of the sensory neuron (say A) to its cell body and, then, along its axon. At the end of the axon of the sensory neuron A, the electrical impulse releases chemical substances called neurotransmitters into the synapse which cross the synapse and start a similar electrical impulse in the dendrites of the next neuron (say B). From the dendrites, this electrical impulse is carried to the cell body and, then, to the axon of the second neuron.
Diagram of a neuron:
(b) Synapses are microscopic gaps present in between pairs of adjacent neurons over which nerve impulses pass from one neuron to the next.
A nerve impulse, on reaching the terminal end of an axon, releases chemicals called neurotransmitters at its tip. These chemicals cross the synapse and start the impulse in the next neuron or to an effector organ.
A receptor in a sense organ is in touch with the dendrites of the sensory neuron. When a stimulus acts on the receptor, a chemical reaction is initiated that produces an electrical impulse in the receptor. This impulse travels from the dendrites of the sensory neuron (say A) to its cell body and, then, along its axon. At the end of the axon of the sensory neuron A, the electrical impulse releases chemical substances called neurotransmitters into the synapse which cross the synapse and start a similar electrical impulse in the dendrites of the next neuron (say B). From the dendrites, this electrical impulse is carried to the cell body and, then, to the axon of the second neuron.
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