Sympathetic and Parasympathetic Nervous System Overview

Sympathetic Division

Prepares body for emergencies; 'fight or flight'.

Parasympathetic Division

Conserves energy; 'rest and digest' functions.

Adrenaline

Hormone released during stress; increases alertness.

Neurotransmitter involved in sympathetic responses.

Norepinephrine (NE)

Preganglionic Neurons

Release Acetylcholine in sympathetic nervous system.

Postganglionic Neurons

Release Norepinephrine in sympathetic nervous system.

Dual Innervation

Organ receives input from both autonomic divisions.

Autonomic Tone

Baseline activity level of autonomic nervous system.

Collateral Ganglia

Innervate abdominopelvic organs; include celiac ganglion.

Celiac Ganglion

Innervates stomach, liver, pancreas, and spleen.

Innervates small intestine and proximal large intestine.

Superior Mesenteric Ganglion

Innervates kidneys and urinary bladder.

Inferior Mesenteric Ganglion

Swollen segments of sympathetic axons.

Varicosities

Adrenergic Receptors

Bind norepinephrine; involved in sympathetic responses.

Bind acetylcholine; involved in parasympathetic responses.

Cholinergic Receptors

Short-term Memory

Immediate recall; does not last long.

Long-term Memory

Stable memories; can be secondary or tertiary.

Memory Consolidation

Process of converting short-term to long-term memory.

Hippocampus

Brain region essential for memory consolidation.

Stage of sleep associated with dreaming.

REM Sleep

Membrane lining body cavities; reduces friction.

Parietal Serosa

Visceral Serosa

Membrane covering organs; allows smooth movement.

Negative Feedback

Counteracts changes to maintain homeostasis.

Positive Feedback

Enhances changes; moves body away from homeostasis.

Cerebral Cortex

Stores most long-term memories; involved in recall.

Limbic system component; involved in emotional memory.

Amygdaloid Body

SNS Preganglionic fibers

Relatively short, Ganglia located near spinal cord

SNS Postganglionic fibers

Relatively long, except at adrenal medullae

Where are the cell bodies of preganglionic neurons located for the sympathetic system?

In the thoracic and lumbar spinal cord regions (T1–L2/L3)

Where are the cell bodies of preganglionic neurons located for the parasympathetic system?

Brainstem (cranial nerves III, VII, IX, and X) and sacral spinal cord (S2–S4)

What type of axons do preganglionic neurons have?

Myelinated axons

What neurotransmitter do preganglionic neurons release?

Acetylcholine (ACh)

Where do preganglionic neurons synapse?

In autonomic ganglia, where they connect with postganglionic neurons.

Short preganglionic axons

Sympathetic Divison

Long preganglionic axons

Parasympathetic Divison

What is the function of preganglionic neurons?

To transmit signals from the CNS to autonomic ganglia, initiating autonomic responses.

What cranial nerves have preganglionic nuerons?

III (oculomotor) VII (facial) IX (glossopharyngeal) X (vagus)

Where are the cell bodies of postganglionic neurons located?

In autonomic ganglia outside the central nervous system (CNS).

What type of axons do postganglionic neurons have?

Unmyelinated axons.

What neurotransmitter do sympathetic postganglionic neurons usually release?

Norepinephrine (NE).

What type of receptors are found on sympathetic target organs?

Adrenergic receptors.

What is the function of postganglionic neurons?

To transmit signals from autonomic ganglia to the target organs or tissues.