What is the preganglionic neurotransmitter of the parasympathetic system?
In the autonomic nervous system (ANS), nerve fibers that connect the central nervous system to ganglia are known as preganglionic fibers. Learning Objectives Key Points
Key Terms
Preganglionic Neuron PropertiesIn the autonomic nervous system (ANS), fibers from the central nervous system to the ganglion are known as preganglionic fibers. All preganglionic fibers, whether they are in the sympathetic nervous system (SNS) or in the parasympathetic nervous system (PSNS), are cholinergic—that is, these fibers use acetylcholine as their neurotransmitter—and are myelinated. The ANS is unique in that it requires a sequential two-neuron efferent pathway; the preganglionic neuron must first cross a synapse onto a postganglionic neuron before innervating the target organ. The preganglionic, or first neuron will begin at the outflow and will cross a synapse at the postganglionic, or second neuron’s cell body. The postganglionic neuron will then cross a synapse at the target organ. Sympathetic preganglionic fibers tend to be shorter than parasympathetic preganglionic fibers because sympathetic ganglia are often closer to the spinal cord while parasympathetic preganglionic fibers tend to project to and synapse with the postganglionic fiber close to the target organ. Outflow SitesProperties of the SNS and PSNS preganglionic neurons also differ with respect to the spinal cord exit points. The sympathetic division has thoracolumbar outflow, meaning that the neurons begin at the thoracic and lumbar (T1–L2) portions of the spinal cord. The parasympathetic division has craniosacral outflow, meaning that the neurons begin at the cranial nerves (CN3, CN7, CN9, CN10) and sacral (S2–S4) spinal cord. The sympathetic division (thoracolumbar outflow) consists of cell bodies in the lateral horn of the spinal cord (intermediolateral cell columns) from T1 to L2. These cell bodies are GVE (general visceral efferent) neurons and are the preganglionic neurons. There are several locations where preganglionic neurons create synapses with their postganglionic neurons:
The parasympathetic division (craniosacral outflow) consists of cell bodies from one of two locations: the brainstem (cranial nerves III, VII, IX, X) or the sacral spinal cord (S2, S3, S4). These are the preganglionic neurons that synapse with the postganglionic neurons in these locations: Parasympathetic ganglia of the head: The parasympathetic division has craniosacral outflow, meaning that the neurons begin at the cranial nerves (CN3, CN7, CN9, CN10) and the sacral (S2–S4) spinal cord. Pre- and post-ganglionic fibers and targets are depicted.
DivergenceAnother major difference between the two ANS systems is divergence, or the number of postsynaptic fibers a single preganglionic fiber creates a synapse with. Whereas in the parasympathetic division there is a divergence factor of roughly 1:4, in the sympathetic division there can be a divergence of up to 1:20. The site of synapse formation and this divergence for both the sympathetic and parasympathetic preganglionic neurons does, however, occur within ganglia situated within the peripheral nervous system. What is the preganglionic neurotransmitter of the parasympathetic system answer?Preganglionic neurons of the sympathetic and parasympathetic divisions and postganglionic neurons of the parasympathetic nervous system utilize acetylcholine (ACh). Postganglionic neurons of the sympathetic nervous system use norepinephrine and epinephrine.
What is the preganglionic neurotransmitter of both sympathetic and parasympathetic?Both sympathetic and parasympathetic preganglionic neurons are cholinergic, meaning they release acetylcholine (Ach) at the synapse in the ganglion. In the parasympathetic system, postganglionic neurons are also cholinergic.
What is the neurotransmitter of the parasympathetic nervous system?The PNS uses acetylcholine as its neurotransmitter for both pre- and postganglionic neurons activating muscarinic receptors. This differs from the SNS, which uses norepinephrine, which acts on adrenergic receptors, as the primary neurotransmitter for most postganglionic neurons.
What is the preganglionic neurotransmitter?Acetylcholine is the preganglionic nerve neurotransmitter, and norepinephrine is the postganglionic neurotransmitter, except for the sweat glands, which have a sympathetic cholinergic innervation.
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