Visual and Auditory Pathways Flashcards
outermost layer of the eye
cornea and sclera
for protection, refraction and transmitting of light
middle layer of the eye
vascular layer
choroid, ciliary body, iris
what connects ciliary body to the lens
suspensory ligament
what happens to the lens when ciliary body contracts
fattens and light is more focused
secretion and absorption of aqueous humour
blocking of reabsorption
ciliary body secretes and reabsorbed by scleral venous sinus or canal of Schlemm
blockage leads to glaucoma (pressure on retina) -> blindness if untreated
muscles of the iris
circularly arranged sphincter pupillae and radially arranged dilator pupillae
role of choroid
supplies nutrients to the retina
when retina detaches it lacks nutrients and oxygen
inner most layer of the eye
neural layer - retina
layers of the retina
rods and cones (furthest from light path)
bipolar cells
pathway of signals from rods and cones
[] rods and cones - bipolar cells
retinal ganglion cells - lateral geniculate nucleus - primary visual cortex
axons of which cells form the optic nerve
retinal ganglion cells
continuation of optic nerve
continues as optic chiasma - optic tract - lateral geniculate nucleus …
axons from nasal and temporal hemiretinas at the optic chiasma
axons from nasal cross the midline
axons from temporal do not cross
result of some axons from retina crossing the midline at the optic chiasm
the left visual field of both eyes is represented on the right visual cortex
and vice versa
primary visual cortex
where axons from lateral geniculate nucleus terminate in the occipital lobe
two streams of visual processing from the primary visual cortex
‘what’ stream to temporal lobe
‘where’ stream to parietal lobe
where do axons that mediate the afferent part of pupillary light reflex terminate
what mediates the efferent part
Edinger Westphal nucleus
parasympathetic fibres in the oculomotor nerve (to intrinsic and extrinsic muscles of the eye)
route of oculomotor nerve
given off from the midbrain
passes along lateral wall of cavernous sinus and enters the orbit
motor supply by oculomotor nerve
most of the extraocular muscles that move the eyeball and intrinsic muscles of the eye (including eyelid)
fibres of oculomotor nerve
where do they synapse
preganglionic parasympathetic fibres from cell bodies in EW nucleus
ciliary ganglion
lesion of oculomotor nerve
paralysis of many extraocular muscles
diplopia
loss of light response
loss of accommodation
route of trochlear nerve
only cranial nerve to emerge from dorsal aspect of brainstem
passes along lateral wall of cavernous sinus and enters orbit
motor supply of trochlear nerve
one of the extraocular eye muscles
lesion of trochlear nerve
causes paralysis of one of the extraocular muscles
diplopia
route of abducens nerve
leaves brain at pontomedullary junction
runs across sharp edge of petrous temporal bone
passes through cavernous sinus and enters orbit
motor supply of abducens nerve
one of the extraocular eye muscles
lesion of abducens nerve
paralysis of one of the extraocular muscles
diplopia
patients presents with medial deviation of affected eye
may result from sepsis or thrombosis in cavernous sinus
cochlea
role
part of the inner ear
organ of hearing
role of semicircular canals
sense head position and rotation
embedding of inner ear
dense structure of temporal bone
dense enough to conduct sound via bone as well as the sound that comes via ear canal
interior of cochlea
three fluid filled tubes
uppermost is the scala vestibule
scala media is between
lowermost compartment is scala tympani
basilar membrane partition between media and tympani
role of basilar membrane in cochlea
mechanical analyser of sound frequency
physical properties are not uniform, tighter regions resonate with higher pitch, distal (more floppy) resonate with lower pitch
basilar membrane mechanical properties along its length
5x broader at apex (base of cochlea)
thicker and tauter toward the base
organ of Corti
receptor organ of the inner ear
vestibulocochlear nerve route
leaves pontomedullary junction
enters internal acoustic meatus together with facial nerve
sensory supply of vestibulocochlear nerve
sensory cells of the inner ear
cochlear portion and vestibular portion of vestibulocochlear nerve
cochlear portion derives from bipolar neurons in spiral ganglion
innervate hair cells of cochlea
vestibular portion arises from bipolar neurons in vestibular ganglion
innervate sensory cells of semicircular canals as well as saccule
lesion of vestibulocochlear nerve
loss of hearing or vestibular sense
vertigo
tinnitus
cochlear nucleus
cochlear nerve sends branches to dorsal and ventral cochlear nuclei
superior olivary nucleus input
how does it localise sound
receives input from each cochlear nucleus
medial portion compares time of arrival of signal at each ear
lateral portion compares sound intensities
inferior colliculus input and projections
what is it responsible for
receives input from cochlear nucleus / superior olivary nucleus
projects to medial geniculate nucleus of the thalamus
responsible for reflex orienting to auditory stimuli
medial geniculate nucleus role and projections
thalamic relay nucleus
projects to ipsilateral primary auditory cortex
primary auditory cortex location and role
effect of stimulation and damage
superior aspect of temporal lobe
receives primary auditory information from both ears
stimulation leads to tinnitus and damage leads to slight hearing loss of affected side
auditory association cortex location and role
superior temporal gyrus
left side is essential for understanding speech
