Autonomic Nervous System Vocabulary

Flashcards defining key vocabulary terms, structures, receptors, and functions of the Autonomic Nervous System based on 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 low level of continuous activity under normal conditions (both sympathetic and parasympathetic) that allows the nervous system to both increase and decrease the activity of an organ.

Preganglionic Neuron

An autonomic neuron whose cell body is located in the brainstem or spinal cord and whose axon is usually lightly myelinated.

Postganglionic Neuron

An autonomic neuron whose cell body is located in an autonomic ganglion outside the CNS and whose unmyelinated axon innervates the target tissue.

Hypothalamus

The primary informatory center for the internal environment that coordinates autonomic functions.

Limbic Cortex

The brain region responsible for providing the integration of emotions into the regulation of the autonomic nervous system.

Sympathetic Division

The thoracolumbar system of the ANS with preganglionic neurons in spinal cord segments Th1 to L3, associated with the 'fight or flight' reaction and energy expenditure.

Parasympathetic Division

The craniosacral system of the ANS with preganglionic neurons in the brainstem (cranial nerves III, VII, IX, X) and sacral spinal cord (S2-S4), associated with 'rest and digest' roles and energy conservation.

Paravertebral Ganglia

Ganglia forming the sympathetic chain where short preganglionic sympathetic fibers synapse.

Prevertebral Ganglia

Autonomic ganglia (including celiac and superior/inferior mesenteric ganglia) where preganglionic sympathetic fibers synapse.

Acetylcholine (ACh)

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

Norepinephrine (NE)

The neurotransmitter used by most postganglionic sympathetic neurons.

Adrenal Medulla

A modified sympathetic ganglion that releases epinephrine directly into the bloodstream 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 upon activation.

Muscarinic (M) Receptors

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

$\alpha_1$ Adrenergic Receptors

Sympathetic receptors located on target tissues that mediate vasoconstriction of most blood vessels.

$\beta_1$ Adrenergic Receptors

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

$\beta_2$ Adrenergic Receptors

Sympathetic receptors that mediate vasodilation in skeletal muscle and bronchodilation in the lungs.

Enteric Nervous System (ENS)

Often called the 'mini-brain' of the gut, a system within the wall of the GIT that regulates motility and secretion independently, while being modulated by the sympathetic and parasympathetic divisions.

Mydriasis

Pupil dilation produced by sympathetic stimulation.

Miosis

Pupil constriction produced by parasympathetic stimulation.