Sensory Cranial Nerves - V, VII, VIII, IX, X Flashcards
The sulcus limitans forms the outer margin of what structure in the adult?
Outer margin of the floor of the fourth ventricle
Which cranial nerves (other than I and II) have sensory components? (5)
V, VII, VIII, IX, X
What is unique about the location of the spinal nucleus of V? Which 4 cranial nerves project to it?
It extends as a column from the mesencephalon to the spinal cord (is continuous with the substantia gelatinosa of the spinal cord at that point); V, VII, IX, X
Which 3 CNs project to the nucleus Solitarius?
VII, IX, X - rostral part is concerned with taste
Where do axons from the nasal epithelium that are part of CN I synapse? WhT are they known as after that?
Olfactory bulb - then project as olfactory tract to olfactory cortex, amygdala and other forebrain structures
_________ is the loss of the sense of smell.
Anosmia
CN II is made of axons of ______ _______ cells.
Retinal ganglion (cells)
Optic nerves from each eye converge just outside the __________. Central to the optic chiasm, the fibers run as the optic ______.
Mesencephalon; tract
What structure does the optic tract run through on its way to. The primary visual cortex?
Lateral geniculate body (visual thalamus)
Optic nerve fibers bypassing the lateral geniculate nucleus that travel to the superior colliculus are important for what?
Visual “startle” reflexes
V1=?, V2=?, V3=? What kind of sensory info is carried by trigeminal nerves?
V1= opthalmic nerve
V2= maxillary nerve
V3= mandibular nerve
*carry epicritic (fine touch, proprioception) and protopathic (pain and temperature)
What innervates the back of the head?
Spinal nerves from C2
Which nucleus relieves epicritic afferents from the face? (Fine touch, vibration sense)
Chief sensory nucleus of V (located in rostral pons)
Where do epicritic afferents in the face region have their cell bodies located?
Trigeminal (Gasserian) ganglion
* is analogous to DRG
What other 3 nerves other than V also carry afferents with fine touch afferents? Where do they synapse?
VII, IX, X –> Chief sensory nucleus of V, it is this the first integration center for all fine touch and vibration inputs to the face (epicritic info)
Which nucleus contains the cell bodies of proprioceptive afferents from the muscles of mastication? Location?
Mesencephalic nucleus of V; located in the Tegmentum of the mesencephalon
*is essentially a displaced peripheral ganglion
What nucleus receives protopathic (pain and temp) afferents from face? Other than V, what 3 other CNs also bring their protopathic afferents to synapse there?
Spinal nucleus of V; VII, IX, X
Where do protopathic afferents in V have their cell bodies located?
Trigeminal ganglion
What is the tract that runs from the chief sensory nucleus of av to the VPM of thalamus?
Trigeminal leminiscus —> takes epicritic input, is therefore analogous to the posterior column/medial leminiscus for spinal pathways
* pathway passes to contralateral side before synapsing in the VPM
What is the name for the tract between the spinal nucleus of V to the VPM of the thalamus?
Trigeminothalamic tract—-> carries protopathic fibers
* 2nd order neurons are contralateral by the time they synapse in the VPM
Afferents from which 3 CNs are located most dorsally in the spinal tract and nucleus of V?
VII, IX, X; then V3, V2, V1—> as goes from dorsal to ventral
What two sensory components does VII have?
Taste: anterior 2/3 of tongue
Somesthetic afferents: for small area around the external auditory meatus (fine touch, vibration, pain, and temperature)
Where are cell bodies for somesthesic afferents of CN VII located?
Geniculate ganglion
From the geniculate ganglion what nucleus do epicritic fibers of VII project to? Protopathic fibers?
From geniculate ganglion:
- epicritic : chief sensory nucleus of V
- protopathic: spinal nucleus of V
What is the rostral portion of the nucleus solitarius known as? What three CNs does it receive input from?
Gustatory nucleus
CN VII : anterior 2/3 of tongue
CN IX : posterior 1/3 of tongue
CN X : pharynx and epiglottis
What is the caudal part of the solitary nucleus known as?what kind of input does it receive?
Cardio respiratory nucleus—> receives visceral sensory input (glands, chemoreceptors, baroreceptors) carried by VII, IX, X
CN VIII has a sensory component with what two divisions?
- Vestibular –> balance and acceleration (body position in space)
- Auditory –> hearing
* both located in the inner ear
What organ are auditory receptors found on in the cochlea?
Organ of Corti
* the receptors are called hair cells
What kind of cells are vestibular receptors? In what three places are they located?
Hair cells ; located in—>
- Saccule
- Utricle
- 3 semicircular canals
In what ganglion are cell bodies of auditory afferents located? Where do they synapse?
Spiral ganglion—> dorsal and ventral cochlear nuclei
- synapse ipsilaterally; cochlear nuclei found at the pontomedullary junction
From the dorsal and ventral cochlear nuclei, what two structures do auditory afferents pass through to reach the auditory cortex (Heschel’s gyrus, transverse gyrus in temporal lobe)
Inferior colliculus—> medial geniculate body (auditory thalamus)
The vestibular division of CN VIII is responsible for what three functions?
- Adjustment of posture
- Regulating muscle tone
- Coordination of eye movements
What ganglion do vestibular hair cells synapse on?
Vestibular (Scarpa’s) ganglion –> these send their axons in the vestibular division of the vestibululocochlear nerve
Axons leaving the vestibular ganglion synapse in the vestibular nuclei, which four are there?
Superior, lateral, medial, inferior
What are the 2 functions of the lateral vestibulospinal tract, coming from the lateral vestibular nucleus?
Controls balance and extensor tone
What is the function of the medial vestibulospinal tract that arises from the medial and inferior vestibular nuclei?
Controls head and neck position (only extends to cervical levels of the cord)
What is the function of the medial longitudinal fasciculus, which arises from medial and superior vestibular nuclei?
Is important for coordinating eye movements
Afferents from carotid sinus (baroreceptors) and carotid body (chemoreceptors) are carried by CN IX and project to where (what nucleus)?
Caudal part of the solitary nucleus and tract
From where does CN X carry info from baroreceptors and chemoreceptors ?
Aortic arch
From where does CN X carry protopathic info from?
Small portion of external ear; also from posterior meninges
What CN mediates the afferent limb of the gag reflex? To what nucleus do they project?
CN IX –> caudal solitary nucleus
In which nucleus is the interneuron between the afferent and efferent parts of the Gag reflex?
Nucleus ambiguous
What CN mediates the efferent response of the gag response?
CN X (motoneurons from N. Ambiguous whose axons travel with CN X)
