This document discusses the peripheral and autonomic nervous systems. It describes the major structures of the peripheral nervous system, including the 12 cranial nerves and 31 spinal nerve pairs, and their functions. It differentiates between afferent and efferent neurons. It also describes how the autonomic nervous system regulates body functions through the sympathetic and parasympathetic nervous systems in a manner that is outside of voluntary control.

1. Peripheral and Autonomic
Nervous Systems
EHS Unit 4

2. Learning Targets
• Discuss major structures in the Peripheral
Nervous system and their functions.
• Differentiate between afferent and efferent
neurons.
• Describe body regulation via the autonomic
nervous system.

3. The Peripheral nervous System
• This includes the 12 pairs of cranial nerves,
the 31 pairs of spinal nerves, and all nerve
pathways in the body outside the brain and
spinal cord.
– Divided into the Somatic and Autonomic Divisions
– Contains afferent and efferent nerve pathways.

4. Nerve Pathways
Afferent (Sensory)
• Brings information to the
central nervous system
from the body.
Efferent (Motor)
• Sends messages from the
CNS to the body tissues.

5. Cranial Nerves
• These are the 12 pairs of nerves that stem from the base of the
brain.
– I Olfactory (smell)
– II Optic (Sight)
– III Occulomotor (Eye Movement)
– IV Trochlear (Eye Movement)
– V Trigeminal (Sensation in face, chewing)
– VI Abducens (Eye movement)
– VII Facial (expressions, taste)
– VIII Vestibulochoclear (Hearing)
– IX Glossopharyngeal (swallowing, taste)
– X Vagus (vital organ control and sensation)
– XI Accessory (muscles in neck)
– XII Hypoglossal (tongue movement)

6. Remember the Cranial Nerves
• On Old Olympia’s Towering Top, A Friendly
Viking Grew Vines And Hops
• Olfactory, Optic, Oculomotor, Trochlear,
Trigeminal, Abducens, Facial,
Vestibulocochlear, Glossopharyngeal, Vagus,
Accessory, Hypoglossal

7. Spinal Nerves
• These are the pairs of nerves that branch off the
spinal cord.
– The dorsal (posterior) root of each nerve is the
sensory (afferent) pathway.
– The ventral (anterior) root is the motor (efferent)
pathway.
• Most nerves simply branch off from the roots to
go out into the body. Some form a plexus.

8. Spinal Nerve Pathways

9. Spinal Nerve Plexus
• A plexus is a junction
or network of several
nerves and blood
vessels.
– The largest plexus is
the sciatic nerve
plexus, which
branches off the
bottom of the spinal
cord and enervates
the legs.
– Others include:
cervical, brachial,
lumbar.

10. The Autonomic Nervous System
• This is the division of the nervous system that
controls the vital functions of the body. It is
outside of voluntary control.
– It controls smooth muscles, glands, regulated
cardiac rhythm, manages function of the vital
organs.
– It is a subdivision of the peripheral nervous system
– It is divided into the sympathetic and
parasympathetic nervous systems.

11. Efferent Pathways in the Autonomic
Nervous System
• Chains of neurons form ganglia that enervate
target organs.
– This is different from the somatic division of the
ANS, which has one long axon that reaches from
the CNS to the target tissue.
– These are motor neurons – they create movement
or action.

12. Overlap of the Systems
• Some functions that are primarily autonomic
can be managed at least in part by voluntary
control (somatic nervous system).
– Higher brain function can override our reflexes
and can effect the response of our autonomic
nervous system. (A mind-over-matter action)
• Ex: Trained snipers are able to slow their heart rates
and breathing to steady their weapons, despite dealing
with adrenaline/anxiety.
• Biofeedback – consciously observing autonomic body
status and focus on changing it.