Autonomic Nervous System - Chapter 15 (TOP HAT Notes)

Vocabulary flashcards covering key concepts of the Autonomic Nervous System, including structure, divisions, pathways, neurotransmitters, receptors, and functional terms.

Autonomic Nervous System (ANS)

Motor division of the Peripheral Nervous System that innervates cardiac muscle, smooth muscle, and glands; operates involuntarily and includes the sympathetic and parasympathetic divisions.

Two-neuron motor unit (Autonomic)

A two-neuron pathway: preganglionic neuron in the CNS releases ACh onto an autonomic ganglion; postganglionic neuron in the ganglion releases ACh or NE onto an effector organ.

Preganglionic neuron

Cell body in the brain or spinal cord; releases acetylcholine (ACh) onto the autonomic ganglion; myelinated.

Postganglionic neuron

Cell body in the autonomic ganglion; releases ACh or norepinephrine (NE) onto the target organ; unmyelinated.

Autonomic ganglion

Cluster of neuronal cell bodies where the preganglionic and postganglionic neurons synapse.

Cholinergic receptors

Receptors that bind acetylcholine (ACh); include nicotinic and muscarinic receptors.

Nicotinic receptors

Ionotropic cholinergic receptors located on autonomic ganglia and the adrenal medulla; activation excites the postsynaptic cell.

Muscarinic receptors

Metabotropic cholinergic receptors located on parasympathetic target organs (and some sympathetic targets); effects can be excitatory or inhibitory depending on the organ.

Adrenergic receptors

Receptors that bind norepinephrine or epinephrine; include alpha and beta subtypes with typically excitatory or inhibitory actions depending on the tissue.

Alpha-adrenergic receptors

Usually excitatory; increase Na+ permeability and cellular activity in target tissues.

Beta-adrenergic receptors

Most have inhibitory effects by increasing K+ permeability and Cl- dynamics in target tissues; exceptions occur in the heart where NE can increase rate and force.

Acetylcholine (ACh)

Neurotransmitter used by cholinergic fibers; released by all preganglionic neurons and parasympathetic postganglionic neurons; quickly degraded by acetylcholinesterase.

Norepinephrine/Epinephrine (NE/Epi)

Neurotransmitter released by most sympathetic postganglionic neurons; longer-lasting; can act as a hormone when released from the adrenal medulla.

Sympathetic division

“Fight or Flight” division; thoracic and lumbar preganglionic fibers; synapses in chain ganglia; postganglionic fibers innervate many organs.

Parasympathetic division

“Rest and Digest” division; craniosacral with long preganglionic fibers; ganglia near target tissues; short postganglionic fibers.

Dual innervation

Most visceral organs receive fibers from both sympathetic and parasympathetic divisions, allowing precise control.

Dynamic antagonism

Both divisions are usually active; one exerts predominant control to fine-tune organ activity.

Cooperative effects

Divisions work together for a common function; e.g., external genitalia: parasympathetic promotes arousal (lubrication, erection) and sympathetic promotes orgasm (ejaculation).

Adrenal medulla

Neuroendocrine organ that releases norepinephrine and epinephrine into the bloodstream when stimulated by preganglionic sympathetic fibers.

Sweat gland innervation

Sympathetic postganglionic fibers to sweat glands are cholinergic (release ACh), not adrenergic.

White ramus

Myelinated preganglionic sympathetic fibers entering the sympathetic chain.

Gray ramus

Unmyelinated postganglionic sympathetic fibers exiting the chain to reach target organs.

Sympathetic chain ganglia

A vertical row of ganglia alongside the vertebral column where most preganglionic sympathetic neurons synapse.

Prevertebral (collateral) ganglia

Sympathetic ganglia located anterior to the aorta; postganglionic fibers travel via splanchnic nerves to abdominal organs.

Splanchnic nerve

Preganglionic sympathetic bundle that travels to collateral ganglia to innervate visceral organs.

Vasomotor tone

Partial continuous sympathetic activity that maintains a baseline level of vascular contraction to regulate blood pressure.