Peripheral Nervous System (PNS)

What structures make up the peripheral nervous system (PNS)?

• Cranial nerves and ganglia
• Spinal nerves and ganglia/plexuses

How many pairs of cranial nerves are in the PNS?

• 12 pairs

How do cranial nerves exit the skull?

• Through the foramina of the skull

How many pairs of spinal nerves are there?

• 31 pairs

How do spinal nerves exit the vertebral column?

• Through the intervertebral foramina

How are the 31 pairs of spinal nerves divided?

• 8 cervical
• 12 thoracic
• 5 lumbar
• 5 sacral
• 1 coccygeal

What is the primary function of peripheral nerve fibers and axons?

• Conduct information to and from the CNS

What supports bundles of peripheral nerve fibers and axons?

• Connective tissue

How are peripheral nerves protected?

• Encased in fibrous sheaths
• Relatively unprotected compared with the CNS

What does the anterior root of a spinal nerve carry?

• Motor information
• Away from the CNS
• Efferent fibers

What does the posterior root of a spinal nerve carry?

• Sensory information
• Toward the CNS
• Afferent fibers

What are ganglia?

• Clusters/swellings of nerve cell bodies
• Give rise to peripheral and central nerve fibers

What are the two types of ganglia?

• Sensory ganglia
• Autonomic ganglia

How do you remember anterior vs. posterior spinal roots?

• Anterior = motor = efferent = away

• Posterior = sensory = afferent = toward CNS