Exam #2: Cranial Nerves V Flashcards
What is the functional component of the cochlear nerve?
SSA (Special Somatic Afferent)–hearing
Where are the cell bodies of the 1st order neurons of the auditory pathway located?
Cochlear/ Spiral Ganglion
Where do the dendrites of the cochlear ganglion terminate?
Receptor hair cells of the Organ of Corti
Where do the axons of the cochlear ganglion enter the brain? What happens here?
Pons–axons bifurcate & go to either:
1) Dorsal cochlear nucleus
2) Ventral cochlear nucleus
Where are the second order neurons of the auditory pathway located?
1) Dorsal cochlear nucleus
2) Ventral cochlear nucleus
BOTH of which are in the Pons
What do the axons of the Ventral Cochlear Nucleus form? Where do these axons project?
Axons of the Ventral Cochlear Nucleus form the “Ventral Acoustic Stria” or “Trapezoid Body.” These axons go to:
1) Nucleus of the Trapezoid Body
2) Superior Olivary Nucleus
Others ascend in the lateral lemniscus (LL) & terminate in:
Nucleus of the LL to INFERIOR COLLICULUS
What do the axons of the Dorsal Cochlear Nucleus form? Where do these axons project?
Axons of the Dorsal Cochlear Nucleus form the “Dorsal Acoustic Stria” that ascend the Lateral Lemniscus (LL) & terminate in the INFERIOR COLLICULUS
What auditory nucleus sends projections to the superior olivary nucleus?
Ventral Cochlear Nucleus
What is the function of the superior olivary nucleus in regards to hearing?
Localization of sound
What is the main pathway of hearing after BOTH the Ventral & Dorsal Cochlear Nuclei?
Axons synapse on the Lateral Lemniscus, which projects to the inferior colliculus of the midbrain
What is the function of the inferior colliculus in regards to hearing?
This is the relay nucleus for hearing in the midbrain
Where does the inferior colliculus project?
Medial Geniculate Nucleus (MGN) of the Thalamus
What is the function of the MGN?
Processing of sound INTENSITY & FREQUENCY
Where does the MGN project?
Auditory cortex via the “auditory radiation”
What Brodmann’s areas comprise the primary auditory cortex?
41 & 42
What is the function of the primary auditory cortex in hearing?
- Localization of sound
- Detecting alterations of the pattern of sound
Where else does the MGN project besides the primary auditory cortex? What is the function of these projections?
Secondary cortical areas, which is important for interpretation of:
- Sound
- Voice
- Language
- Music
What are the 3rd order neurons of the auditory pathway?
Superior olivary nucleus
Where is the sensory information to the Superior Olivary Nucleus coming from?
BOTH ears
What is the sound attenuation reflex?
Protective reflex that causes contraction of the tensor tympani & stapedius, dampening auditory input
Outline the neuronal pathway of the sound attenuation reflex.
1) Loud sound at hair cells (organ or corti)
2) Transduction down dendrites of chochlear ganglia
3) Axons of cochlear ganglia project to the ventral cochlear nucleus
4) Ventral cochlear nucleus projects to the superior olivary nucleus
5) Superior olivary nucleus projects onto BOTH the TRIGEMINAL & FACAL NUCLEI
What muscle is innervated by the trigeminal nerve in the sound attenuation reflex?
Tensor tympani
What muscle is innervated by the facial nerve in the sound attenuation reflex?
Stapedius
What is the functional component of the vestibular nerve?
SSA (Special Somatic Afferent)–Equilibrium
What ganglia contains the first order neurons of the vestibular pathway?
Vestibular ganglia or “Scarpa’s Ganglia”
Where are the dendrites of the vestibular ganglia?
1) Hair cells of the maculae or the utricle & saccule
2) Cristae of the semicircular canal ampullae
Where do the axons of the vestibular ganglia project?
- Pons, where they bifurcate & synapse with:
1) Vestibular nuclei
2) Inferior cerebellar peduncle, where they end in the flocculonodular lobe of the cerebellum
What is the flocculonodular lobe of the cerebellum? Why is this important?
This is the region of the cerebellum that coordinates head & eye movement
*****This connection makes the vestibular nerve the ONLY nerve to have a direct connection to the cerebellum
Where are the second order cell bodies of the vestibular pathway located?
Vestibular nuclei