6.4 Nervous System

​6.4 Peripheral Nervous System

​Nerves and ganglia outside the central nervous system

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Nerve = bundle of neuron fibers

Ganglia = nerve cell bodies

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Neuron fibers are bundled by connective tissue.

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​Peripheral Nerves

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​Endoneurium

CT ​that surrounds the axon and myelin sheath

​Perineurium

CT form a fascicle ​that bundles fibers

​Epineurium

CT that bundles fascicles and blood ​vessels

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​Nerve Structure

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​Mixed nerves – both sensory and motor fibers

Afferent (sensory) nerves – carry impulses toward the CNS

Efferent (motor) nerves – carry impulses away from the CNS

Spinal nerves- There is a pair of spinal nerves at the level of each vertebrae.

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​Classification of Nerves

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Multiple Choice

What do motor/efferent neurons do?

• carry messages from the brain and spinal cord to muscles and glands

• carry impulses from the skin and sends to the spinal cord and brain

• carry impulses from sensory neurons to motor neurons

• store messages

• ​Dorsal (posterior)root - transmits from the skin and muscles to the spinal cord

• Ventral (anterior) root – innervate muscle and organ tissues

The dorsal and ventral nerves unite to form the left and right spinal nerves that exit each spinal level.

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​Spinal Nerve Roots

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• ​Dorsal Ramus and Ventral Ramus

  • Carry nerve impulses to the muscle and the skin of the trunk.

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​Spinal Ramus Mixed Nerves

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​Plexuses – complex interconnections of nerves that branch out from the ventral rami

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Most efferent nerves in the neck, arms, and legs originate in the plexuses.

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​Nerve Plexus

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• Parasympathetic

  • NT

    • Acetylcholine (ACh)

  • Receptors

    • Nicotinic (CNS)

    • Muscarinic (PNS)

• Sympathetic

  • NT

    • Norepinephrine (NE)

  • Receptors

    • Nicotinic (CNS)

    • Adrenergic

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Neurotransmitters and Receptors of the PNS

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• ​Fight, Flight, Freeze Response to the 4 E's

  • Emergency

  • Exercise

  • Excitement

  • Embarrassment

• Longer response to NT

  • slow degradation of NE

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Sympathetic Nervous

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​Know These!!

• ​Rest and Digest

  • Functional opposition to the sympathetic

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Parasympathetic Nervous

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​Know These!!