Point 12
Intro
The
primary input to both cochlear nuclei is from the auditory
portion of C.N. VIII. The axons making up this division of
C.N. VIII consist of the central processes of neurons that
lie in the spiral or cochlear ganglion (lies in the modiolus
[bony core] of the cochlea). The peripheral processes of
neurons within the cochlear ganglion end upon the hair cells
comprising the organ of Corti. We will not discuss the organ
of Corti at this time.
Since you will have a series of lectures on the auditory system later in this course I will give you a very CURSORY and INCOMPLETE overview of ascending auditory pathways. Let's trace an ascending pathway from the ventral cochlear nucleus. The axon courses rostrally to reach the pons where it travels in the lateral lemniscus. The axon can travel in the lateral lemniscus until it reaches the inferior colliculus where it synapses. Cell in the inferior colliculus project to the thalamus, and in particular to the medial geniculate body. The medial geniculate body projects to primary auditory cortex in the temporal lobe.
The ascending axon can also give off a
collateral to a structure called the superior olive.
Cells in the superior olive then cross in what is called the
trapezoid body, enter the opposite lateral lemniscus
and eventually reach the inferior colliculus. You can take
it to auditory cortex from here.