Ch. 14 - Parasympathetic Division

Parasympathetic division

"Rest and digest" mode; active when the sympathetic system is inactive; it's energy-conserving

Parasympathetic division characteristics - Craniosacral division

Preganglionic axons arise from the brain and from the sacral region of the spinal cord

Vagus nerve

The most important parasympathetic nerve; supplies heart, lungs, GI tract, pancreas, etc.

Preganglionic neuron

Body is in one of nuclei in brain or in gray matter of spinal cord. Axon travels over a cranial nerve or spinal nerve to reach postganglionic neuron

Postganglionic neuron

Body is in terminal ganglion and axons extends to effector

Parasympathetic ganglia

Pre- and postganglionic neurons of parasympathetic division synapse in terminal ganglia.

Where are parasympathetic ganglia located in regardance to the spinal cord?

In general, they're located the farthest from the spinal cord.

Little divergence of PNS fibers

Preganglionic fibers exhibit minimal branching; therefore individual parasympathetic nerves can be stimulated

How is parasympathetic division activated?

It's not necessarily activated as a whole, but it can exert localized control over effectors

Neurotransmitter released

Preganglionic & postganglionic neurons both release acetycholine (ACh). Note that ACh is rapidly inactivated by acetycholinesterase, therefore the parasympathetic system produces short-term effects

Effects of parasympathetic division on cardiovascular system:

Sweating, pupil dilation, contraction of arrector pili muscles, metabolic rate increase, mental alertness increase, hinders urine formation & voiding

Effects of parasympathetic division on respiratory system:

Constricts bronchioles

Effects of parasympathetic division on digestive system:

Increases activity of digestive system and associated glands

Other effects of parasympathetic division:

Constricts pupil and promotes voiding of urine