What are neurons, and how do they transmit signals in the nervous system?

Ans: Neurons are specialized cells that are the fundamental building blocks of the nervous system. They are responsible for transmitting signals, called nerve impulses or action potentials, throughout the nervous system, enabling communication between different parts of the body and facilitating the control of various physiological functions and behaviors.

Transmission of Nerve Impulses:

The transmission of nerve impulses is a highly coordinated process involving electrical and chemical signals. Here’s how it works:

a). Resting Membrane Potential: Neurons have a resting membrane potential, which is an electrical charge difference across their cell membranes. This is due to the uneven distribution of ions (charged particles) inside and outside the cell. At rest, there is a higher concentration of sodium ions (Na+) outside the cell and a higher concentration of potassium ions (K+) inside the cell. This creates a negative charge inside the neuron relative to the outside.

b). Action Potential: When a neuron is stimulated, either by another neuron or by sensory input, the resting membrane potential can change. If the stimulus is strong enough and reaches a threshold level, it triggers an action potential.

An action potential is a rapid, brief reversal of the membrane potential, causing a sudden change from negative to positive charge inside the neuron.

This change is achieved through the opening and closing of ion channels in the cell membrane, allowing sodium ions to rush into the cell, depolarizing it, and then allowing potassium ions to flow out, repolarizing it.

The action potential travels along the length of the axon like a wave, propagating the electrical signal toward the axon terminals.

c). Synaptic Transmission: When the action potential reaches the axon terminals, it triggers the release of neurotransmitters from vesicles into the synaptic cleft (the small gap between the axon terminal of one neuron and the dendrite or cell body of another).

Neurotransmitters are chemical messengers that transmit the signal from one neuron to the next.

They bind to receptors on the postsynaptic neuron, leading to changes in the postsynaptic membrane potential (either excitatory, making it more likely to generate an action potential, or inhibitory, making it less likely).

d). Integration of Signals: The postsynaptic neuron integrates the excitatory and inhibitory signals it receives from multiple synapses. If the net effect is depolarization beyond a threshold, it generates its action potential and passes the signal to the next neuron in the circuit.

e). Propagation: The action potential travels down the axon, repeating the process of depolarization and repolarization until it reaches its destination, where it can trigger a response (e.g., muscle contraction or secretion of a neurotransmitter at a synapse).

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