Autonomic Nervous System - Vocabulary Flashcards

Vocabulary flashcards covering key ANS concepts from the lecture notes.

Autonomic nervous system

The motor nervous system that controls glands, cardiac and smooth muscle, and adipose tissue; operates involuntarily to maintain homeostasis.

Sympathetic division

Division of the ANS that prepares the body for 'fight or flight' by increasing alertness, metabolism, heart rate, respiration, and energy mobilization; generally inhibits digestion.

Parasympathetic division

Division of the ANS that conserves energy and promotes 'rest and digest' activities, decreasing heart rate and promoting digestion and urination.

Dual innervation

Most organs receive input from both sympathetic and parasympathetic divisions, usually with opposite effects for fine control.

Enteric nervous system

A subdivision of the ANS that governs the gastrointestinal tract; can function independently but is considered part of the ANS.

Two-motor-neuron chain

The ANS pathway from CNS to target involves two neurons (preganglionic and postganglionic) with a ganglion in between; somatic system uses one neuron.

Preganglionic neuron

Neuron with cell bodies in the CNS; its axon (preganglionic fibre) synapses with the ganglionic (postganglionic) neuron.

Postganglionic neuron

Neuron with cell bodies in autonomic ganglia; its axon (postganglionic fibre) extends to the effector organ.

Autonomic ganglia

Clusters of neuron cell bodies outside the CNS where preganglionic and postganglionic neurons synapse (e.g., sympathetic chain, collateral, parasympathetic ganglia).

Sympathetic trunk ganglia

Series of chain ganglia adjacent to the spinal column where most sympathetic preganglionic fibres synapse.

Collateral (prevertebral) ganglia

Ganglia located anterior to the spinal column; receive splanchnic nerve input and innervate abdominal viscera (e.g., celiac, superior/inferior mesenteric).

Adrenal medulla

Neurosecretory tissue that acts as a modified sympathetic ganglion; releases epinephrine and norepinephrine into the blood.

Thoracic and superior lumbar segments

Spinal cord segments where sympathetic preganglionic neurons originate in the lateral horn and exit via ventral roots.

Parasympathetic preganglionic origin

Cell bodies in brainstem and sacral spinal cord; preganglionic fibers are long and synapse near or within target organs.

Cranial nerves carrying parasympathetic fibers

III (oculomotor), VII (facial), IX (glossopharyngeal), X (vagus); plus pelvic nerves from sacral segments.

Vagus nerve

Cranial nerve X; provides about 75% of parasympathetic outflow to thoracic and abdominal organs.

Neurotransmitters of the ANS

All preganglionic fibers release acetylcholine (ACh); parasympathetic postganglionic fibers release ACh; most sympathetic postganglionic fibers release norepinephrine (NE); adrenal medulla releases epinephrine and NE into blood.

Cholinergic fibers

Fibers that release acetylcholine (ACh).

Adrenergic fibers

Fibers that release norepinephrine (noradrenaline); some sympathetic fibers release ACh; adrenal medulla releases epinephrine.

Cholinergic receptors

Receptors that respond to acetylcholine; include nicotinic and muscarinic types.

Nicotinic receptors

Cholinergic receptors located on all autonomic ganglia and neuromuscular junctions; excitatory when bound by ACh.

Muscarinic receptors

Cholinergic receptors on parasympathetic target organs; can be excitatory or inhibitory; mediated by G-proteins.

Adrenergic receptors

Receptors for norepinephrine and epinephrine; include alpha and beta subtypes with varying effects.

Alpha and Beta receptors

Subtypes of adrenergic receptors: α1, α2, β1, β2, β3; tissue-specific responses (e.g., vasoconstriction, increased heart rate).

Autonomic tone

Baseline level of activity in the ANS that modulates organ function even at rest.

Local visceral reflexes

Visceral reflexes that operate at a local level without requiring a whole-body response (e.g., swallowing reflex, pupil dilation in low light).