Human Anatomy

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Human Anatomy

• Peripheral Nervous System
• PNS
• Part I

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2 Components of PNS

• 12 pr. of cranial nerves
• 31 pr. of spinal nerves
• So.what is a nerve?

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Structure of a Nerve
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Structure of a Nerve

• Connective tissue organized similar to muscle
• Epineurium surrounds the entire nerve

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Structure of a Nerve

• 2. perineurium surrounds a fascicle

Fascicle a bundle of axons
fascicle
perineurium
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Structure of a Nerve
Fascicle
Perineurium
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Structure of a Nerve

• 3. Endoneurium surrounds each axon

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Types of Nerves

• Sensory all axons in all fascicles going from
  periphery to spinal cord
• Motor all axons in all fascicles going from
  spinal cord to skeletal muscle (or other organs)
• Mixed axons within the nerve going in different
  directions BUT not within the same fascicles.
• All axons within a single fascicle are going in
  only one direction

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Structure of a Nerve
Axons
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Cranial Nerves (12)
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Cranial Nerves

• Found on inferior surface of brain

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Cranial Nerves

• Some are sensory n.
• Periphery (skin or other organs) to brain
• Some are motor n.
• Brain to periphery (muscle or another organ)
• Some are mixed n.
• Both directions
• All 12 pr. can be used to test various areas of
  the brain
• For instance.

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The Optic Nerve
A patient comes in with a vision problem
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Study Hint for the Cranial Nerves

• Make a table with 6 columns
• The headings for the 6 columns (L to R) should
  be
• Number
• Name
• S, M, or B (B mixed)
• Function
• Test
• Special features

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I Olfactory

• Sensory
• Olfaction
• Bulb

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I Olfactory
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I Olfactory
Olfactory bulb Cribriform plate
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Location of Olfactory Bulb
Cribriform plates
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II Optic

• Sensory
• Vision
• Comprised of axons from rods and cones of retina

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II Optic
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Extrinsic Eye Muscle

• Six muscles that attach to eyeball and are
  responsible for moving (gazing) the eye within
  the orbit.

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Extrinsic Eye Muscles

• Names
• Superior rectus
• Inferior rectus
• Lateral rectus
• Medial rectus
• Superior oblique
• Inferior oblique

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III, IV and VI

• Cranial n. III, IV and VI innervate the 6
  extrinsic eye muscles
• All 3 nerves are pure motor nerves
• III oculomotor
• IV trochlear
• VI -- abducens

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Extrinsic Eye Muscles

• Which nerve innervates which muscle(s)?
• LR6SO4
• Superior rectus III
• Inferior rectus III
• Lateral rectus VI
• Medial rectus III
• Superior oblique IV
• Inferior oblique III

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V Trigeminal

• Three divisions (branches) of V V1, V2 and V3

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V Trigeminal

• V1 ophthalmic branch, purely sensory

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V Trigeminal

• V2 maxillary branch, purely sensory

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V Trigeminal

• V3 mandibular branch, both motor and sensory
  a mixed nerve branch
• Therefore, because V3 is a mixed nerve, the
  trigeminal nerve has to be considered a mixed
  cranial nerve.

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V3 Trigeminal

• Motor to muscles of mastication (chewing)

sensory
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Tic Douloureux

• Sudden discharge of V2 and V3
• Causes intense pain to areas innervated by V2 and
  V3
• Trigeminal neuralgia
• 1/25,000 and usually 40 yo and older

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VII Facial
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VII Facial

• Mixed
• Motor to facial muscles (5 branches)
• Sensory from taste buds anterior 2/3 of the
  tongue
• Exits through stylomastoid foramen
• Bells Palsey -- dysfunction of VII because of
  viral inflammation
• Results in facial muscle paralysis on one side
• Usually cures itself within weeks or a few
  months

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VII Facial
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VIII Vestibulocochlear

• Semicircular canals balance abd equilibrium
• Cochlea
• hearing

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VIII Vestibulocochlear

• Sensory
• Hearing and balance
• Cochlea and semicircular canals

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IX Glossopharyngeal
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IX Glossopharyngeal

• Mixed
• Motor to
• Swallowing muscles of pharynx
• Parotid salivary gland (saliva producing)
• Sensory from
• Taste from posterior 1/3 of tongue
• Lining of pharynx
• Soft palate

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X Vagus

• Longest cranial n. in
• human body
• Innervates head, neck,
• thorax and abdomen

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X Vagus

• Mixed
• Motor to
• Pharyngeal and laryngeal muscles
• Organs in thorax and abdomen
• Lungs and heart
• Liver, stomach, intestines

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X Vagus
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X Vagus

• Mixed
• Sensory from
• Pharynx
• External auditory canal
• Organs of thorax and abdomen

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X Vagus
Vagotomy to inhibit gastric acid secretion
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XI Accessory
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XI Accessory

• Motor
• Motor to
• Sternocleidomastoid
• Trapezius
• Pharyngeal and laryngeal muscles

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XII Hypoglossal

• Motor to muscles of the tongue
• Tongue points to side of lesion