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Peripheral and Autonomic Nervous Systems
EHS Unit 4
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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.
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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.
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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.
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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)
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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
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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.
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Spinal Nerve Pathways
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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.
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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.
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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.
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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.