Question

What triggers depolarization?

Answer 1

Nerve conduction:

1. The neurons conduct nerve impulses when the neuronal membrane is polarized and depolarized.

Polarization:

1. When the neuron is at a resting state i.e not conducting nerve impulse, the axonal membrane becomes more permeable to K⁺ ions and impermeable to Na + ions and it also becomes impermeable to negatively charged proteins.
2. The axoplasm membrane Inside the axon contains a high concentration of K⁺ ions, a high concentration of negatively charged proteins, and a low concentration of sodium ions.
3. The fluid outside the axon or outer side of the axon membrane contains a low concentration of K⁺ ions and high concentration of Na⁺ ions, thus forming a concentration gradient, which is maintained by a sodium-potassium pump, which transports two K⁺ inside the cell membrane and three Na⁺ ions outwards the cell membrane, thus the outer surface of axonal membrane acquires a positive charge, while the inner surface of axonal membrane acquires a negative charge.
4. The process by which an axonal membrane acquires positive and negative charges (polarized) is called polarization.

Depolarization :

1. The process by which the polarity of the axonal membrane changes when the nerve cell receives a stimulus is called depolarization.
2. Depolarization occurs when the stimulus is applied to the polarized membrane, then the membrane becomes permeable to Na⁺ ions, which leads to the rapid influx of Na⁺ ions, thus polarity of the membrane changes and becomes depolarized (membrane acquires a positive charge on the outer surface and negative charge on the inner surface), which leads to conduction of nerve impulse.