Vestib [2] Speech aph [3] Flashcards
trace the pathway for the central auditory system
sound → cochlear hair cells → ANFs in spiral ganglion→
(auditory nerve) enters brainstem and bifurcates (DCN+VCN) →
(some cross trapezoid body) →
Superior olive / Lateral lemniscus →
Inferior colliculus →
Medial geniculate nucleus (thalamus) →
auditory radiations →
Primary auditory cortex (superior temporal gyrys)
Unilateral lesions in Inferior collicus or above results in what sort of deficits?
Sound source localization deficits contralateral to the lesion
(since ITDs and ILDs are are representatives for sound source localizations
Dpes Unilateral lesion @ Inferior collicus affect hearing ?
No deafness (even unilaterally) bc its heavily innervated by neurons from both ears.
Primary auditory cortex
Posterior neurons vs anterior neurons in terms of freq
Broadmanns area 41 (deep to lateral sulcus)
Anterior neurons: ↓ f
Posterior neurons: ↑ f
ITDs
phase locking (temporal coding of periodicity of sound)
MSO
↓ freq
sound localization
ILDs
rate coding of sound intensity
LSO
↑ f
Vestibular sys mapping
1° axons → terminate in vestibular ganglia → DESCENDS as medial/lateral vestibulospinal tract → vestibular nuclei → ASCENDS + forms MLF → CN III, IV, VI
The otolith organs detect _______ of the head and position with respect to gravity, whereas the semicircular canal organs detect _________.
linear acceleration
Angular acceleration
Utricular hair bundles project vertically, tilting head from the horizontal causes ______.
shearing between the hair cells and overlying otolithic membrane.
- Utricle therefore informs the brain of the position of the head with respect to gravity.
(linear acceleration in horizontal direction)
(hair cells point towards axis of polarity (striola) and optimizes range of signal detected)
- maximally excited and saccule is maximally inhibited
saccular hair bundles project horizontally, and are sensitive to ______.
vertical displacements of the head (elevator) and informs the brain of linear acceleration in vertical direction.
- maximally excited and utricle is maximally inhibited
head rotation (angular rotation) will lead to movement of endolymph fluid w/in the canal and deflection of the _____
cupula: which changes hair cell receptor potential
Excitation of fibers in this tract will lead to excitation of extensor muscles of the limbs and participate in postural reflexes asssociated with utricular sensation of gravity
Lateral vestibulospinal tract.( whose axons comes from the lateral nucleus, who recieves its afferents from the UTRICLES)
excitation of fibers in these tracts will lead to important coordination of eye and head movements
medial longitudinal fasciculus, medial vestibulospinal tract (whose axons come from the medial and superior vestibular nuclei, who gets their projections from semicircular canals)
the saccule, utricle, semicircular canals, and spinal and cerebellar input, and all project to the ___________
vermal cerebellum
mental status exam:
- cognitive deficits →
- neuro exam →
- cognitive deficits → syndrome dx
- neuro exam → localized site
together can lead to etiologic dx + tx
