Page 454 - Fundamentals of anatomy physiology

Figure 12–16 Events in the Functioning of a Cholinergic Synapse. Chapter 12 Neural Tissue 441
Calcium ions (Ca2+) enter the cytosol of the axon terminal.
1 An arriving action potential depolarizes the axon terminal of a 2
This results in ACh release from the synaptic vesicles by
presynaptic neuron. exocytosis.

Mitochondrion Mitochondrion Voltage-gated
11 Ca2+ channel

AA Synaptic 2 A 2
Ch Ch vesicle Ca2+ Ch

A A Ca2+
Ch Ch
A A
Ch Ch

2 2

Axon terminal AA
Ch Ch

Synaptic cleft 12

Postsynaptic neuron ACh receptor
(chemically
gated Na+
channel)

3 ACh diffuses across the synaptic cleft and binds to 4 Depolarization ends as ACh is broken down into acetate and

receptors on the postynaptic membrane. Sodium channels choline by AChE. The axon terminal reabsorbs choline from the
open, producing a graded depolarization. synaptic cleft and uses it to resynthesize ACh.

Mitochondrion

Acetyl-CoA CoA

A 4 A A
Ch Ch Ch Ch
Acetylcholine

Axon terminal

A 3 A 3 Choline Ch Acetylcholinesterase A
Ch Ch 4 (AChE) Ch

Acetate A

Na+ Chemically Initiation of a Postsynaptic neuron Propagation
gated Na+ Na+ graded potential, of action
potential
channels or action potential, if
threshold is reached (if generated)
at the initial segment