Cranial Nerves

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Cranial Nerves
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cranial nerves

• provide
• motor (or efferent) and
• sensory (or afferent)
• Innervation for the head, neck, thorax and
  abdomen.
• They are called cranial nerves because they
  emerge through foramina in the cranium and are
  covered with tubular sheaths formed from the
  cranial meninges

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Oh Oh Oh To Touch And Feel Very Green Vegetables
A H
Olfactory Optic Oculomotor Trochlear
Trigeminal Abducens Facial Vestibulococlear Gloss
opharangeal Vagus Accessory Hypoglossal
I II III IV V VI VII VIII IX X XI XII
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The Cranial Nerves
There are 12 pairs of cranial nerves and they are
continuous with the brain and are numbered from
anterior to posterior, according to the their
attachment to the brain.
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The cranial nerves provide motor (or efferent)
and sensory (or afferent) innervation for the
head, neck, thorax and abdomen. They are called
cranial nerves because they emerge through
foramina in the cranium and are covered with
tubular sheaths formed from the cranial meninges.
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Cranial Nerves and Nuclei

• they can be systematized in terms of their
  function components contained within each nerve.
• Spinal nerves contain both motor and sensory
  components.
• Some of each kind may be related to visceral or
  somatic structures.
• A given nerve fibre can thus be put into the
  following categories

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Function Components of the Cranial Nerves

• No cranial nerve contains all seven functional
  components.
• There are 3 types of cranial nerves
• Those that contain GSE fibres and little or
  nothing else (e.g., CN III, IV, VI and XII) and
  are referred to as somatic efferent nerves
• Those that contain special sensory fibres (SSA or
  SVA) and nothing else (e.g., CN I, II and VIII)
• And the remaining nerves that are more complex,
  contain several components including the
  innervation of the branchial arch musculature
  (e.g., CN V, VII, IX, X and XI). These nerves are
  called branchiomeric nerves.

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Somatic

• Afferent
• General Somatic Afferent (GSA)
• These fibres are related to the receptors for
  pain, temperature, and mechanical stimuli in
  somatic structures such as skin, muscle and
  joints.
• Special Somatic Afferent (SSA)
• These fibres are related to the special senses of
  sight, hearing and equilibrium.

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Somatic

• Efferent
• General Somatic Efferent (GSE)
• These fibres innervate skeletal muscle (i.e.,
  they are the axons of the alpha and gamma motor
  neurons).

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Visceral

• Afferent
• General Visceral Afferent (GVA)
• These fibres are related to the receptors of the
  visceral structures such as the walls of the
  digestive tract.
• Special Visceral Afferent (SVA)
• These fibres are related to the special senses of
  smell and taste.

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Visceral

• Efferent
• General Visceral Efferent (GVE)
• These are fibres that are the preganglionic
  autonomic fibres.
• Special Visceral Efferent (SVE)
• These fibres innervate certain striated muscles
  with a special embryological origin.
• They are referred to as the branchiomeric
  muscles.
• Structures that develop into gill arches in fish
  develop instead into various structures near or
  in the head and neck (muscles of the face, larynx
  and pharynx).
• Although these muscles are identical to normal
  striated muscle, neurons for branchiomeric
  muscles have a distinctive location in the
  brainstem.

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Somatic Efferent Nerves

• This includes the oculomotor (CN III), trochlea
  (CN IV), abducens (CN VI) and hypoglossal (CN
  XII) nerves.
• These nerves are the simplest of the cranial
  nerves as each contains only one functional
  component (GSE fibres).
• The exception is for CN III, which has a small
  but important complement of GVE fibres.
• The nuclei of origin of all these nerves are
  located adjacent to the midline near the aqueduct
  or the floor of the 4th ventricle.

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The Branchiomeric Nerves

• This includes the trigeminal (CN V), facial (CN
  VII), glossopharyngeal (CN IX), vagus (CN X) and
  accessory (CN XI) nerves.
• All these nerves innervate striated muscle of
  branchial arch origin (i.e., they all contain SVE
  fibres).
• With the possible exception of CN XI, they all
  contain other components as well.

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