Neuroscience
Online

Section I:
Cellular and Molecular Neurobiology

11. Acetylcholine Neurotransmission
Part 2 of 8

Jack C. Waymire, Ph.D.

Anatomy
Cell Biology
Physiology
Behavior and Clinical

Acetylcholine in the Autonomic Nervous System

In the autonomic nervous system, acetylcholine (ACh) is the neurotransmitter in the preganglionic sympathetic and parasympathetic neurons. These are shown in Figure 11.2 as the red ACh in the ganglion. ACh is also the neurotransmitter at the adrenal medulla and serves as the neurotransmitter at all the parasympathetic innervated organs. ACh is also the neurotransmitter at the sweat glands, and at the piloerector muscle of the sympathetic ANS (Labeled in blue in Figure 11.2).

Figure 11.2.

Peripheral and autonomic sites where ACh is neurotransmitter.

ACh in the Peripheral Nervous System

In the peripheral nervous system, ACh is the neurotransmitter at the neuromuscular junction between the motor nerve and skeletal muscle.

ACh in the Central Nervous System

In the central nervous system, ACh is found primarily in interneurons, shown in Figure 11.3 as orange and green cell clusters. A few important long-axon cholinergic pathways have also been identified. Noteworthy is the cholinergic projection from the nucleus basalis of Meynert (in the basal forebrain) to the forebrain neocortex and associated limbic structures, represented by the black pathway in Figure 11.3. Degeneration of this pathway is one of the pathologies associated with Alzheimer's disease. There is also a projection from the medial septal and diagonal band region to limbic structures (blue). Most subcortical areas are innervated by neurons from the ponto-mesencephalic region (purple in Figure 11.3).

Figure 11.3.

Distribution of cholinergic cell groups and projections in the rat brain.

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