Peripheral and Autonomic Nervous Systems

EHS Unit 4

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.

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.

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.

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)

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

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.

Spinal Nerve Pathways

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.

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.

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.

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.