Autonomic Nervous System Flashcards

Comprehensive vocabulary flashcards detailing the anatomical structure, receptors, neurotransmitters, and physiological actions of the autonomic nervous system.

Autonomic Nervous System (ANS)

Part of the nervous system composed of sympathetic and parasympathetic divisions that innervates visceral organs, glands, and blood vessels to regulate organ function.

Sympathetic Nervous System Origin

Thoracolumbar region, with preganglionic cell bodies located in the lateral horn of spinal cord segments T1 to L2/L3.

Parasympathetic Nervous System Origin

Craniosacral region, originating from cranial nerve nuclei (CN III, VII, IX, X) and sacral spinal cord segments S2 to S4 (pelvic splanchnic nerves).

Preganglionic Neurons

Autonomic neurons with cell bodies in the central nervous system (CNS) that synapse in autonomic ganglia.

Postganglionic Neurons

Autonomic neurons with cell bodies in autonomic ganglia that extend axons to synapse directly on effector organs.

Chromaffin Cells

Specialized cells in the adrenal medulla that receive direct preganglionic sympathetic innervation and secrete $80\%$ epinephrine and $20\%$ norepinephrine into circulation.

Pheochromocytoma

A tumor of the adrenal medulla that secretes excessive amounts of catecholamines, leading to increased urinary excretion of 3-methoxy-4-hydroxymandelic acid (VMA).

Adrenergic Neurons

Neurons of the autonomic nervous system that synthesize and release norepinephrine as their neurotransmitter.

Cholinergic Neurons

Neurons in both the sympathetic and parasympathetic nervous systems that synthesize and release acetylcholine (ACh) as their neurotransmitter.

Peptidergic Neurons

Parasympathetic postganglionic neurons that release non-classical peptide neurotransmitters such as vasoactive intestinal peptide and substance P.

Autonomic Synaptic Transmitters Pathway Diagram

A diagram illustrating preganglionic ACh release across all ANS divisions, postganglionic parasympathetic ACh release, and postganglionic sympathetic norepinephrine (NA) release.

Alpha-1 ($\alpha-1$) Receptors Summary

Postsynaptic receptors located on vascular smooth muscle, pupillary smooth muscle (mydriasis), and pilomotor smooth muscle (erects hair) that induce contraction.

Alpha-2 ($\alpha-2$) Receptors

Mostly presynaptic adrenergic receptors on nerve terminals, fat cells, and platelets that inhibit neurotransmitter release and lipolysis while stimulating platelet aggregation.

Beta Receptors Summary

Includes $\beta-1$ receptors (located in heart to stimulate rate and force) and $\beta-2$ receptors (located in smooth muscle, liver, and pancreatic B cells to relax smooth muscle, stimulate glycogenolysis, and stimulate insulin release).

Nicotinic Receptors

Cholinergic receptors located in autonomic ganglia, neuromuscular junctions, and adrenal medulla that open $\text{Na}^+$ and $\text{K}^+$ channels to produce excitation.

Muscarinic Receptors

Cholinergic receptors in the heart, smooth muscle, and glands that produce inhibitory effects in the heart and excitatory effects in smooth muscle and glands; blocked by atropine.

Medulla Oblongata ANS Centers Diagram

Brainstem region shown housing autonomic centers including the vasomotor center, respiratory center, swallowing center, coughing center, and vomiting center.

Pneumotaxic Center

An autonomic respiratory center located in the pons.

Micturition Center

An autonomic regulatory center located in the midbrain.

Chronotropic Effect

Refers to heart rate regulation; sympathetic stimulation via $\beta_1$ receptors produces a positive (+ve) effect, while parasympathetic stimulation produces a negative (-ve) effect.

Dromotropic Effect

Refers to cardiac conduction velocity; sympathetic stimulation via $\beta_1$ receptors produces a positive (+ve) effect, while parasympathetic stimulation produces a negative (-ve) effect.

Autonomic Effects on Genital Function

Sympathetic stimulation induces ejaculation (emission), whereas parasympathetic stimulation induces erection through vasodilatation.