Neurohumoral transmission occurs in the autonomic nervous system.
Nerve impulses travel along axons quickly. Then, they reach the nerve endings.
Here, the process switches to chemical signaling. First, an action potential arrives at the presynaptic terminal.
Immediately, voltage-gated calcium channels open. Calcium ions rush in rapidly.
As a result, synaptic vesicles move forward and fuse with the membrane.
Consequently, neurotransmitters release into the synaptic cleft through exocytosis.
Next, these chemicals diffuse across the gap swiftly.
Then, they bind to specific receptors on the postsynaptic membrane or effector cells.
This binding activates ion channels or second messengers. Therefore, it triggers excitation or inhibition.
For example, acetylcholine acts as the main preganglionic transmitter in both sympathetic and parasympathetic divisions.
Moreover, postganglionic parasympathetic neurons also release acetylcholine.
In contrast, most sympathetic postganglionic neurons release norepinephrine instead.
Finally, after the response, enzymes or reuptake mechanisms remove the neurotransmitters quickly. Thus, the signal terminates promptly.
This entire sequence ensures precise control over body functions.