Anatomy and Physiology of the Peripheral and Autonomic Nervous System

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.