Download Nolte Chapter 12 – Cranial Nerves and Their Nuclei

Nolte Chapter 12 – Cranial Nerves and Their Nuclei
somatic sensory and motor columns extend the length of the spinal cord.
Visceral sensory and motor columns are found at spinal levels T1 to L3 and S2 to S4
Branchiomeric muscles refer to those are associated with the larynx, pharynx, jaw, and face.
Motor Only: III, IV, VI, XII
Sensory: I, II, VIII
Branchiomeric: V,VII, IX, X, and XI
Some say money matters, but my brother says big brains buy more
Upper motor neurons that supply motor nuclei are known as corticobulbar neurons. Their axons
accompany the corticospinal tract until they reach the brainstem levels of the nuclei they innervate.
Occulumotor
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controls the eyelid and all the internal and external muscles of the ipsilateral eye except the
lateral rectus(abducens) and superior oblique(trochlear).
originate in the oculomotor nucleus which is in the rostral midbrain at the ventral edge of the
periaqueductal gray.
o the edinger westphal nucleus straddles the midline and projects to the siliary ganglion.
emerges out of the brainstem into the interpeduncular fossa
Trochlear
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controls the superior oblique of the contralateral(only one) eye
originates in the trochlear nucleus at the level of the inferior colliculus (rostral midbrain)
o indents the MLF
leave the brainstem on the rostral side(only one to do so) at the pons-midbrain junction.
Abducens
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supplies the ipsilateral lateral rectus
originate in the abducens nucleus of the caudal pons beneath the floor of the fourth ventricle.
o medial to it are the MLF and the facial nerve.
exits the pons-medulla junction.
the facial nerve wraps around the dorsal part of the abducens nucleus after they leave the facial
nucleus
o this “genu” of the facial nerve, in conjunction with the abducens forms the facial
colliculus.
The abducens also projects to the contralateral occulomotor nucleus
o ascend through the MLF to help pull the medial rectus of the contralateral eye at the
same time one moves contracts the lateral rectus of the ipsilateral eye.
Hypoglossal
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controls the tongue
originates in the ipsilateral hypoglossal nucleus in the caudal medulla/ rostral medulla.
o this nucleus is adjacent to the midline beneath the floor of the fourth ventricle and
forms an elevation known as the hypoglossal trigone
leaves through the rooflets in the groove between the pyramid and the olive.
Trigeminal
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gives rise to tactile, proprioception, and pain for the face
has three primary afferent types : ophthalmic, maxillary, and mandibular
o mandibular like a chin strap, maxillary from below nose to bottom lip, ophthalmic
everything above.
the sensory components have three nuclei
o main sensory nucleus in the midpons
 received information about touch and jaw position
 gives rise to pathways to the thalamus
 one crosses and joins the medial lemniscus and goes to VPM
 the other is uncrossed(respresents the inside of the mouth) and goes up
its own path in the dorsal trigeminal tract.
o spinal nucleus in the more caudal pons
 receives information about pain and temperature
 this nucleus gradually blends with lissauer’s tract
 have to turn caudally first to get down to the caudal pons and in so doing make
the spinal trigeminal tract
 The somatic afferent fibers of VII, IX, X all enter the spinal trigeminal
tract
 might also receive some pain that comes from glossopharyngeal.
 they then join the spinothalamic tract to head to the VPM
o mesencephalic nucleus more rostral pons and into midbrain.
 this is technically a part of the trigeminal gangion located within the CNS
because its cells are pseudounipolar and their processes collect in a bundle
called the mesencephalic trigeminal tract
trigeminal motor nucleus
o innervates the muscles of the first branchial arch, which are mainly concerned with
mastication. also includes the tensor tympani
o located in the midpons at the level of attachment of the trigeminal nerve to the
brainstem.
The somatic afferent fibers of VII, IX, X all enter the spinal trigeminal tract. They also contain some
visceral components that enter a discrete budle called the solitary tract. This tract is unusual in that it
surrounds its nucleus (the nucleus of the solitary tract in the caudal medulla).
Facial
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deals with facial expression
the facial motor nucleus is in the caudal pons in the ventrolateral tegmentum.
lower motor neurons project to ipsilateral face muscles
Glossopharyngeal
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convery information from intaoral receptors like the carotid body, sinus, ear cavity, mucous
membrane, the pharynx, and the taste-buds posterior third of the tongue.
its visceral sensory fibers enter the solitary tract and synapse in its nucleus
o pain, however, enters the spinal trigeminal tracts and terminates in the spinal nucleus.
somatic sensation from the outer eat heads to the inferior salivary nucleus
branchial motor fibers like the pharynx (swallowing and speaking) arise from cells in the nucleus
ambiguous which is the the ventrolateral medullary tegmentum, just dorsal to the inferior
olivary nucleus.
Vagus
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the principal parasympathetic nerve
similar in its connections to the glossopharayngeal.
mostly travel to the thoracic and abdominal viscera
motor projects to viscera arise in the dorsal motor nucleus of the vagus, which is just lateral the
hypoglossal, which is in the rostral/caudal medulla and exits lateral to the olive.
o this forms a little elevation on the floor of the fourth ventricle called the vagal trigone.
its afferents enter the spinal trigeminal tract and terminate in the spinal trigeminal nucleus.
its branchial motor projections arise in the nucleus ambiguous(ventrolateral medullary
tegmentum) and innervate the pharynx and larynx
o gag reflex: afferents are gloss, efferents are vagus.