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12 Cards in this Set
- Front
- Back
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1st order neuron
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Neuron that is associated with the hair cells in the Organ of Corti and has projections to the dorsal and ventral cochlear nucleiis
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3 components of nerve cells
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Each neural cell has a dendrite and axon and cell body.
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Where are cell bodies of 1st order neurons located
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You can see their cell bodies in the Spiral Ganglion in the lower right of the figure.
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How do the neurons comprising the auditory pathway travel through and to the brain stem and auditory cortex?
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The neurons comprising the auditory pathway don’t course uninterruptedly through the brain stem and then on to the auditory cortex of the cerebrum. Rather, there is a succession of at least four neurons between the cochlea and cerebral cortex.
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Describe the succession of neurons.
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Those at the level of the spiral ganglion are called First Order Neurons. They all terminate in the cochlear nuclei where they synapse with Second Order Neurons, while the nerve fibers that originate with the next synapse are called Third Order Neurons, and so on, to the cortical level.
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Explain how the cochlear branch of the auditory nerve is formed
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The central processes of the spiral ganglion cells pass to the core of the modiolus where they form the cochlear branch of the auditory nerve. The most apical fibers follow a straight course and form the core of the nerve, while the basal fibers are added in a twisted fashion to form the periphery of the nerve. So the high frequency fibers are the most exposed and subjected to trauma, while the more essential for speech reception, the lower frequency fibers, are somewhat protected.
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What joins the cochlear nerve as it enters the internal auditory meatus?
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As the cochlear nerve enters the internal auditory meatus, it is joined by the two divisions of the vestibular nerve to complete the auditory nerve, which lies in close proximity to the facial nerve.
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How long is the auditory nerve?
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5mm
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Describe where the auditory nerve enters the brain and how it divides into branches
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The auditory nerve enters the medulla oblongata laterally at the level of the lower pons, where the cochlear bundle courses directly to the cochlear nu cleus where it divides into 2 branches. One branch descends to the dorsal part of the nucleus and the other ascends to the ventral cochlear nucleus. The fibers of both branches terminate in synapses with second order neurons of the cochlear nuclei.
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the tract/canal of all the spiral ganglion that circle around from the base to the apex of the cochlea.
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The Canal of Rosenthal
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PERIPHERAL DENDRITIC EXTENSION
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nerve extension that travels through the perforate habenula and extends up to terminate at the base of the hair cell. The dendritic extensions may contact a number of hair cells, and each hair cells may have more than one peripheral dendritic extension at its base. The hair cell is the most peripherally located sense organ for hearing.
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Central axonal extension
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Moving toward the brain stem or cortex, nerve fibers exit the bony capsule of the cochlea through the modiolus at the base, and then they project either into the VENTRAL COCHLEAR NUCLEUS or the Dorsal Cochlear Nucleus in the brain stem.
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