DLA 28 + lecture 27+28 Flashcards
function of lateral rectus eye muscle innervation
abduction CN VI (abducens)
medical rectus function
innervation
adduction CN III (oculomotor)
superior rectus function
innervation
elevation during abduction
intorsion during adduction
CN III
inferior rectus function
innervation
depression during abduction
extorsion during adduction
CN III
superior oblique function
innervation
depression during adduction
intorsion during abduction
CN IV (trochlear N)
inferior oblique function
innervation
elevation during adduction
extorsion during abduction
CN III
medial longitudinal fasciculus
in control of vertical eye movements
found in the midbrain
pontine paramedianmreticular formation (PPRF)
participates in saccadic eye movements and lateral gaze
horizontal gaze center
located in pons
vestibular nuclei
extend from the pons to the medulla
contribute to the control of eye movements
cerebellum and eye movements
Vestibulocerebellum (flocculo-nodular lobe)
participates in the control of optokinetic movements and smooth pursuit
area 8
frontal eye field (motor control)
visual sensory (motion) input
parieto-occipital eye field
Trochlear Nerve Palsy
deficit of the superior oblique muscle
leaves inferior oblique unopposed
eyes are up and to the right during primary gaze
Oculomotor Nerve Palsy
the will be deviated down and out during primary gaze
lateral rectus muscle is unopposed
usually see ptosis and mydriasis
abducens nerve palsy
eye will be deviated medially
medial rectus muscle is unopposed
diplopia (double vision)
eyes are not pointed at the same target
mismatch of the visual field centers of the eyes
will complain of blurry vision
medial longitudinal fasciculus lesion
prevents adduction of the side with the lesion during lateral gaze
PPRF Lesion
a paralysis of ipsilateral horizontal eye movements
prevents conjugate gaze of both eyes to the side with the lesion
One-and-a-half Syndrome
lesion of both the MLF and the PPRF
prevents adduction of the eye with the lesion
prevents conjugate gaze of the both eyes to the side of the lesion
one eye cannot move lateral
and the other can only move outward
The 3 divisions of the ear
1. external ear (auricle or pinna) collects and amplifies sound external meatus (conducts sound to tympanic membrane)
- middle ear
tympanic membrane (separates external meatus from inner ear)
ossicles (malleus, incus, stapes)
auditory tube (middle ear to nasopharynx) - internal ear
bony labyrinth
membranous labyrinth
bony labyrinth (inner ear)
made up by semicircular canals (anterior, posterior, lateral)
vestibule
cochlea
perilymph
membranous labyrinth (inner ear)
Communicating sacs & ducts suspended within the bony labyrinth
cochlear (cochlear duct)
vestibular (semicircular ducts, utricle, and saccule
endolymph
Perilymphatic space
Between wall of bony labyrinth & wall of membranous labyrinth
low K / high Na (similar to extracellular fluid)
Endolymphatic spaces
contained within the membranous labyrinth
high K / low Na (similar to intracellular fluid)
sensory hairs of the labyrinth
rows of stereocilia
mechanoreceptor transducer channel proteins at the distal ends (communicate with afferent fibers)
2 types of hair cells of the vestibular labyrinth
type I: flask shaped and surrounded by afferent fibers; few efferent
type II: cylindrical shaped
afferent and efferent nerves
sensory regions of the cochlear labyrinth
spiral organ of corti
sensor of sound vibrations
has inner and outer hair cells; supporting cells
spiral ganglion
sensory regions of the vestibular labyrinth
- the semi-circular ducts
3 ampullae each contain crista ampullaris
sensors of angular movement of the head through cupula
Type I and II cells; supporting cells - saccule and utricle
have maculae (oriented at right angles)
sensors gravity and linear acceleration (otolithic membrane)
Type I and II cells; supporting cells
cochlea
around a central core called a modiolus
three compartments:
- scala media (cochlear duct)
endolymph
spiral organ of corti - scala vestibuli
perilymph - scala tympani
perilymph space
the vestibuli and tympani connect at the apex of the cochlea via the helicotrema
scala media or cochlear duct
contains stria vascularis - production and maintenance of endolymph
spiral organ of corti
sensor of sound vibrations
phalangeal and pillar support cells
tectorial membrane (rigid)
gel-like structure
bundles of II, V, and IX collagen; glycoproteins
attached to modiolus
stria vascularis
production and maintenance of endolymph
capillary network
3 types of cells:
- marginal cells - K transport; line endolymphatic space
- intermediate cells- contain pigment; along capillaries
- basal cells - separate from spiral ligament
hair cells of the spiral organ of corti
inner: primary sensory cells for hearing cant regenerate straight line of stereocilia single layer
outer:
variable number of rows
characteristic ‘W’ of stereocilia
play role in amplification
conductive hearing loss
Sound waves are mechanically impeded from reaching the auditory sensory receptors of the internal ear
causes: ear infection lots of ear wax foreign bodies otosclerosis
Sensorineural hearing loss
injury to the sensory receptors, nerves, or auditory cortex
causes: infection of membranous labyrinth fracture of temporal bone acoustic trauma aging
presbycusis
loss of sensory cells
