ANS Human A&P

What does the Autonomic Nervous System (ANS) control?

Smooth muscles, cardiac muscle, and glands.

Is the ANS voluntary or involuntary?

Involuntary

What does the ANS help regulate?

Heart rate, blood pressure, digestion, and blood distribution.

How many neurons are in the ANS motor pathway?

Two – preganglionic and postganglionic.

Where is the cell body of the preganglionic neuron?

In the brain stem or spinal cord.

Where is the cell body of the postganglionic neuron?

In an autonomic ganglion outside the CNS.

What neurotransmitter is released by preganglionic fibers?

Acetylcholine (ACh).

What do postganglionic fibers release?

Norepinephrine (sympathetic) or ACh (parasympathetic).

Are the effects always the same?

No, they can be stimulatory or inhibitory depending on the receptor.

What are the two divisions of the ANS?

Parasympathetic and Sympathetic.

What does dual innervation mean?

Most organs get input from both divisions to maintain balance.

What is the nickname of the parasympathetic division?

“Rest and digest.”

What are three functions it supports?

Digestion, urination, defecation.

What are its effects on the body?

Slows heart rate and breathing, increases digestion, constricts pupils.

What is the nickname of the sympathetic division?

“Fight or flight.”

When is it activated?

During stress: exercise, emergency, excitement.

What changes occur in the body?

Increased heart rate, dilated pupils, glucose release, bronchiole dilation.

Where do parasympathetic fibers originate?

Craniosacral (brain stem and sacral cord).

Where do sympathetic fibers originate?

Thoracolumbar (T1–L2 spinal segments).

Describe the fiber lengths in Parasympathetic

Parasympathetic: long preganglionic, short postganglionic.

Describe the fiber lengths in Sympathetic

short preganglionic, long postganglionic.

Where are parasympathetic ganglia located?

Near or inside target organs.

Where are sympathetic ganglia located?

Near the spinal cord.

What do preganglionic sympathetic fibers pass through to enter the trunk?

White rami communicantes.

What is the sympathetic trunk also called?

Chain or paravertebral ganglia.

How many sympathetic trunk ganglia are there?

23 total: 3 cervical, 11 thoracic, 4 lumbar, 4 sacral, 1 coccygeal.