1. 17.4 The Peripheral Nervous System

2. 17.4 The Peripheral Nervous System
The peripheral nervous system is composed of nerves and ganglia.
Nerves are bundles of axons.
Ganglia are collections of cell bodies.
The peripheral nervous system is subdivided into the somatic system and the autonomic system.

3. spinal nerve dorsal root ventral root dorsal root ganglion
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spinal
nerve
dorsal
root
ventral
root
dorsal root
ganglion b.

4. Somatic System Somatic System
The somatic system serves the skin, skeletal muscles, and tendons.
Some actions in the somatic system are due to reflexes, which are automatic responses to a stimulus.
Most actions in the somatic system are voluntary

5. Somatic System The Reflex Arc
programmed, built-in circuits that allow for protection and survival.
require no conscious thought
Nerve impulses travel from the sensory neuron to the spinal cord and back to the motor neuron.

6. cell body of sensory neuron
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pin
dorsal root ganglion
dorsal horn
central canal
white matter
sensory
receptor
(in skin)
gray matter
Dorsal
dorsal
horn
cell body of sensory neuron
axon of sensory neuron
cell body of interneuron
axon of motor neuron
effector
(muscle)
ventral root
cell body of
motor neuron
ventral horn
ventral horn
Ventral

7. Autonomic System
function automatically and usually in an involuntary manner
regulates the activity of cardiac and smooth muscle and glands.
composed of the sympathetic and parasympathetic divisions.
innervate all internal organs
utilize two motor neurons that synapse at a ganglion.

8. Autonomic System Sympathetic Division Parasympathetic Division
important during emergency situations
“fight or flight” response: adrenalin released, increasing heart rate, increased breathing rate, etc.
Parasympathetic Division
sometimes called the housekeeper division because it promotes all the internal responses we associate with “rest and digest.”

9. Table 17.1