Crash course : Sympathetic Nervous System

Sympathetic Nervous System

The "fight or flight" division of the autonomic nervous system that prepares the body for emergency action.

Thoracolumbar Outflow

The origin of sympathetic nerves from the lateral horns of T1-L2 spinal cord segments.

Sympathetic Chain Ganglia

A chain of ganglia running parallel to the spinal cord where many sympathetic synapses occur.

Spinal Nerve Pathway

Sympathetic pathway that innervates sweat glands, arrector pili muscles, and blood vessels of the skin.

Sympathetic Nerve Pathway

Sympathetic pathway that directly innervates thoracic organs like the heart and lungs.

Splanchnic Nerve Pathway

Sympathetic pathway that innervates abdominal organs through prevertebral ganglia.

Adrenal Medulla

A modified sympathetic ganglion that releases epinephrine and norepinephrine into the bloodstream.

Epinephrine

The primary hormone (80%) released by the adrenal medulla during sympathetic activation.

Norepinephrine

The primary neurotransmitter for most sympathetic postganglionic neurons and a minor hormone (20%) from adrenal medulla.

Cholinergic

Referring to neurons that release acetylcholine as their neurotransmitter.

Adrenergic

Referring to neurons that release norepinephrine as their neurotransmitter.

Nicotinic Receptors

Type of cholinergic receptor found on ALL postganglionic neurons in autonomic ganglia.

Muscarinic Receptors

Type of cholinergic receptor found on effector organs of the parasympathetic system and some sympathetic targets.

Alpha-adrenergic Receptors

Type of adrenergic receptor that typically causes excitatory effects like vasoconstriction.

Beta-adrenergic Receptors

Type of adrenergic receptor that typically causes inhibitory effects like bronchodilation.

Sympathetic Tone

The baseline level of sympathetic activity that maintains partial constriction of blood vessels.

Vasoconstriction

Narrowing of blood vessels, a key sympathetic effect that redirects blood flow.

Vasodilation

Widening of blood vessels; occurs in skeletal muscle blood vessels during sympathetic activation.

Bronchodilation

Widening of airways in the lungs caused by sympathetic stimulation.

Mydriasis

Pupil dilation caused by sympathetic activation of the radial eye muscles.

Cardiostimulation

Increased heart rate and force of contraction caused by sympathetic stimulation.

Hyperglycemia

Elevated blood glucose levels caused by sympathetic stimulation of liver glycogen breakdown.

Preganglionic Neuron

The first neuron in the sympathetic pathway with cell body in spinal cord and axon extending to ganglion.

Postganglionic Neuron

The second neuron in the sympathetic pathway with cell body in ganglion and axon extending to effector organ.

White Rami Communicantes

Myelinated nerve fibers carrying preganglionic sympathetic axons into the sympathetic chain.

Gray Rami Communicantes

Unmyelinated nerve fibers carrying postganglionic sympathetic axons to spinal nerves.

Mass Activation

The sympathetic nervous system's ability to activate multiple organs simultaneously during stress.