A&P 1: Autonomic Nervous System

Preganglionic Neuron

A motor neuron having a cell body located in the brain or spinal cord and a myelinated axon that travels out of the central nervous system as part of a cranial or spinal nerve before separating and extending into the autonomic ganglion.

Postganglionic Neuron

A motor neuron that forms a synapse with one or more preganglionic motor neurons, is located outside the central nervous system and has its unmyelinated axon ending in smooth muscle, cardiac muscle, or a gland.

Cholinergic Fibers

Any of the nerve fibers that transmit impulses to other nerve cells or to muscle fibers or gland cells by acetylcholine.

Parasympathetic Division

The part of the involuntary nervous system that serves to slow the heart rate, increase intestinal and glandular activity, and relax the sphincter muscles. The parasympathetic nervous system, together with the sympathetic nervous system, constitutes the autonomic nervous system.

Sympathetic Division

The sympathetic nervous system (SNS) is part of the autonomic nervous system (ANS), which also includes the parasympathetic nervous system (PNS). The sympathetic nervous system activates what is often termed the fight or flight response

Preganglionic Axon

a fiber the cell body of which is located in an autonomic nucleus in the spinal cord or brainstem and the axon of which terminates in an autonomic (motor) ganglion; found in nerves conveying sympathetic or parasympathetic fibers.

Alpha Receptors

a site on a cell that, upon interaction with epinephrine or norepinephrine, controls vasoconstriction, intestinal relaxation, pupil dilation, and other physiological processes

Beta Receptors

an adrenergic receptor in the sympathetic nervous system, stimulation of which results especially in increased cardiac activity.

Adrenergic Receptors

are a class of G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine (noradrenaline) and epinephrine (adrenaline).

Postganglionic Axon

distal to a ganglion; specifically of, relating to, or being an axon arising from a cell body within an autonomic ganglion

Nicotinic Receptors

is a channel protein that, upon binding by acetylcholine, opens to allow diffusion of cations. The muscarinic receptor, on the other hand, is a membrane protein; upon stimulation by neurotransmitter, it causes the opening of ion channels indirectly, through a second messenger.

Norepinephrine (NE)

is an organic chemical in the catecholamine family that functions in the brain and body as a hormone and neurotransmitter. "Norepinephrine" is also the international nonproprietary name given to the drug.

Acetylcholine (ACh)

is an organic chemical that functions in the brain and body of many types of animals, including humans, as a neurotransmitter a chemical released by nerve cells to send signals to other cells. Its name is derived from its chemical structure: it is an ester of acetic acid and choline.

Muscarinic Receptors

membrane-bound proteins with an extracellular domain that contains a recognition site for acetylcholine (ACh); combination of Ach with the receptor initiates a physiologic change (slowing of heart rate, increased glandular secretory activity, and stimulation of smooth muscle contractions); changes are observed after treatment with the mushroom alkaloid muscarine. Muscarinic receptors are to be distinguished from nicotinic receptors.

Adrenergic Fibers

nerve fibre is a neuron for which the neurotransmitter is either adrenaline (epinephrine), noradrenaline or dopamine. These neurotransmitters are released at a location known as the synapse, which is a junction point between the axon of one nerve cell and the dendrite of another.

Autonomic Nervous System (ANS)

the part of the nervous system responsible for control of the bodily functions not consciously directed, such as breathing, the heartbeat, and digestive processes.