Autonomic Nervous System Review

Vocabulary flashcards covering the general features, structure, divisions, mediators, receptors, and functions of the autonomic nervous system based on the lecture notes.

Autonomic Nervous System (ANS)

A specialized division of the nervous system responsible for the involuntary coordination of bodily functions to preserve the internal environment and ensure homeostasis.

Autonomic Tone

A continuous low level of activity in normal conditions, comprised of sympathetic and parasympathetic tone, allowing the system to both increase and decrease organ activity.

Preganglionic Neuron

An autonomic neuron with its cell body located in the brainstem or spinal cord and an axon that is usually lightly myelinated.

Postganglionic Neuron

An autonomic neuron with its cell body in an autonomic ganglion outside the CNS and an unmyelinated axon that innervates target tissue.

Hypothalamus

The primary informatory center for the internal environment that coordinates autonomic nervous system activity.

Sympathetic Division

Also known as the thoracolumbar system; originates in spinal cord segments Th1 to L3 and triggers the fight or flight reaction to mobilize body energy.

Parasympathetic Division

Also known as the craniosacral system; originates in the brainstem (cranial nerves III, VII, IX, X) and sacral spinal cord (S2-S4), focusing on rest and digest functions.

Acetylcholine (ACh)

The neurotransmitter used by all preganglionic neurons, all postganglionic parasympathetic neurons, and sympathetic fibers innervating sweat glands.

Norepinephrine (NE)

The primary neurotransmitter released by most postganglionic sympathetic neurons.

Epinephrine

A hormone/neurotransmitter released into the bloodstream by the adrenal medulla during stress.

Adrenal Medulla

A modified sympathetic ganglion that secretes epinephrine into the blood during stress.

Nicotinic (N) Receptors

Ligand-gated ion channels located on the cell bodies of all postganglionic neurons and the adrenal medulla that cause rapid depolarization.

Muscarinic (M) Receptors

G-protein coupled receptors located on parasympathetic target tissues that can mediate excitatory or inhibitory responses.

Alpha-1 ($\alpha_1$) Receptors

Adrenergic receptors on sympathetic target tissues that mediate vasoconstriction of most blood vessels.

Beta-1 ($\beta_1$) Receptors

Adrenergic receptors located on the heart that increase heart rate and contractility.

Beta-2 ($\beta_2$) Receptors

Adrenergic receptors that induce vasodilation in skeletal muscle and bronchodilation in the lungs.

Enteric Nervous System (ENS)

Often termed the mini-brain of the gut, it resides within the wall of the gastrointestinal tract to independently regulate motility and secretion.

Mydriasis

Pupil dilation caused by sympathetic activation.

Miosis

Pupil constriction caused by parasympathetic activation.