Human Anatomy

The Autonomic Nervous System

ANS

ANS

• Regulates various physiological processes unconsciously, for instance:

1. Cardiovascular

2. Respiration

3. Digestion

4. Body temperature

5. Excretion

2 Subdivisions of the ANS

1. Sympathetic NS

• “fight or flight”

2. Parasympathetic NS

• “rest and repose”

Anatomy of ANS

• Consists of only 2 neurons1. Preganglionic neuron (#1)2. Ganglionic neuron (#2)• The ganglion is a structure where • the axon of the preganglionic neuron synapses

(release of neurotransmitter) with • the ganglionic neuron (dendrite or cell body)• The axon of the ganglion synapses with the

target cell or organ.

Anatomy of the ANS

• Differences between sympathetic and parasympathetic are:

1. Location of preganglionic (#1) cell body

2. Location of the ganglia

3. Neurotransmitters released at synapses

4. Effects on target organs

Sympathetic Anatomy

• Once again, just 2 cells

• Preganglion (#1) cell body in gray matter of spinal cord ---- levels T1 – L2

• Thoracolumbar system

Sympathetic AnatomyThoraco-lumbar

Sympathetic Anatomy

• Synapse of preganglionic (#1) with ganglionic (#2) neurons happens in the ganglion

• 3 cervical ganglia

• 3 abdominal ganglia

• Neurotransmitter is acetylcholine (ACh)

Sympathetic AnatomyThoraco-lumbar

Sympathetic Ganglia

• Paravertebral ganglia1. Cervical• Superior• Middle• Inferior2. Abdominal• Celiac• Superior mesenteric• Inferior mesenteric

Sympathetic AnatomyThoraco-lumbar

Sympathetic Anatomy

• Ganglionic (#2) axons are relatively long

• Synapse at target cell or organ

• Neurotransmitter is norepinephrine (NE)

Sympathetic AnatomyThoraco-lumbar

Parasympathetic Anatomy

• Once again, just 2 cells

• Preganglionic (#1) cell body in either:

1. Brainstem

2. Spinal cord ---- S2 – S4

• Craniosacral system

Parasympathetic Anatomy

Cranio-sacral

Parasympathetic Anatomy

• Synapse of preganglionic with ganglionic neurons happens in the ganglion

• Ganglia are located on the target organs

Parasympathetic Anatomy

Cranio-sacral

Parasympathetic Anatomy

• Ganglionic axons are relatively short

• Synapse at target cell or organ

• Neurotransmitter is acetylcholine (ACh)

Parasympathetic Anatomy

Cranio-sacral

Summary

FIGURE 17-2p. 445

Summary

• Sympathetic

1. Thoracolumbar

2. Paravertebral ganglia

3. ACh then NE

• Parasympathetic

1. Craniosacral

2. Ganglia at target

3. ACh and ACh

Biological Effects

• Most organs have dual innervation

1. CV

• S – increase heart rate, force of ventricle contraction, increase blood pressure by constricting smooth muscles of arteries

• P -- opposite

Biological Effects

2. Respiration• S – dilation of bronchiole smooth muscle

which increases diameter• P – opposite3. Digestion• S – decreases activity of organs and

glands• P -- opposite

Biological Effects

4. Vision

• S – dilation of pupil

• P – constriction of pupil

5. Reprodction

• S – causes ejaculation in males

• P – sexual arousal (erection) in both sexes