Nerve Impulses. Synapse Structure and Function. Transmission Across a Synapse

Nerve Impulses. Synapse Structure and Function. Transmission Across a Synapse

 

Nerve Impulses When axons are resting, they are not conducting nerve impulses. When they are active, axons are conducting nerve impulses, also called action potentials.Resting PotentialWhen an axon is resting, its membrane is polarized; that is, the outside is positive compared to the inside, which is negative. A protein carrier in the membrane, called the sodiumpotassium pump, pumps sodium (Na+) out of the axon and potassium (K+) into the axon. Another factor that causes the inside of the axon to be negative compared to the outside is the presence of large, negatively charged protein ions inside an axon. The polarity across an axon that is not conducting nerve impulses is called the resting potential (Fig. 8.3a).Action PotentialWhen the nerve fiber is conducting a nerve impulse (action potential), a change in polarity occurs across the axon’s membrane (Fig. 8.3b). First, the inside of an axon becomes positive compared to the outside (this is called depolarization), and...
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