Peripheral Nervous System

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Peripheral Nervous System

• Cranial and spinal nerves

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Spinal Nerves

• There are 31 pairs of spinal nerves
• They branch of the spinal cord and pass between
  the vertebral processes

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Spinal Nerves

• Classified as cervical, thoracic, lumbar, sacral,
  coccygeal
• Nerve to know- phrenic nerve innervates the
  diaphram(C3-C4)

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Spinal Nerve Structure

• Spinal nerves branch out of the spinal cord.
• Dorsal root carries sensory information to
  CNS(afferent)
• Ventral root carries motor information to
  effectors(efferent)
• Ramus is a initial large branching of spinal
  nerve
• Plexus is network of nerves that come together to
  innervate specific regions

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Cranial Nerves

• 12 pairs of nerves that originate mostly from the
  brain stem
• They are numbered and named.
• Can carry sensory, motor or both types of neurons

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Cranial Nerves
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PNS
Somatic NS
Autonomic NS
Voluntary control
Sympathetic NS
Parasymathetic NS
Norepinephrine
Epinephrine
Acetylcholine
Prevents over-stimulation of involuntary action
Normal stimulation of involuntary action
fight or flight
rest and repair
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Sympathetic Nervous System

• Neurotransmitters
• Norepinephrine-stimulates normal functioning of
  the smooth and cardiac muscles
• Epinephrine-causes flight or fight response
• Increased heart rate and strength of contraction
• Dilation of blood vessels in muscles
• Constriction of blood vessels in digestive system
• Dilated airways and increases respiration rate
• Increased conversion of glycogen to glucose

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Parasympathetic Nervous System

• Neurotransmitter
• Acetylcholine- reverses the effects of
  norepinephrine to maintain homestasis
• Slows the heart rate
• Increase rate of peristalsis
• Stimulates digestive and salivary glands

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Reflex Arc

• Reflex can be either muscular or glandular.
• It is a predicted response to a particular
  stimulus.

Sensory receptor
Sensory neuron
Interneuron(association) neuron
Motor neuron
Affector(muscle or gland)
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Reflex Arc
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Disorders of PNS

• Shingles(herpes zoster) is a viral infection
  usually caused by the varicella virus(chicken
  pox)
• It usually affects on dermatome
• Dermatome is a specific region of skin innervated
  by a given spinal nerve
• Mytome is specific muscle group innervated by one
  spinal nerve

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Disorders of PNS

• Sciatica
• Causes severe pain in the leg caused by
  compression, irritation, or inflammation of the
  sciatic nerves, which are thick nerves extending
  down the back of each leg.

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Disorders of PNS

• Neurofibromatosis
• Tumors start in the schwann cells of the
  peripheral nervous sys
• Tumors can be mild(Cafe Au Lait) spots or
  disfiguring tumors