ANS, visual, hearing pathways Flashcards
outer layer of eye
cornea - transparent, a-vascular, refraction
sclera - white opaque area, muscles insert for eye movement
middle, vascular layer of eye
choroid- vascular, nourishes cornea, retina
iris- pigmented, vascular, muscles which change diamater of pupil
ciliary body- controls shape of lens via suspensory ligaments
lens- biconvex, A-vascular
inner layer of eye
retina (extension of diencephalon)
features of non-neuronal layer of retina
pigmented epithelium, sitting against choroid of eye.
absorbs light
maintains the metabolic activity of photoreceptors
provides cap. to the photoreceptors
features of neuronal layer of retina
photoreceptors
1st order bipolar neurones
2nd order ganglion nuerones
optic disk –> point where axons of ganglion neurones leave the retina to become the optic nerve
interneurones: horizontal and amacrine interneurones
photochemical reactions occur here
features of rods
20 x more common, sensitive to light, vision in dim-light, high level of convergence
found everywhere
features of cones
colour vision, high visual acuity, lower levels of convergence , at macula= one cone for every ganglion cell
found in macula/ fovea/ not in periphery
the visual pathway is a 3 neurone chain. the optic nerves will combine to cross at …
the optic chiasm: hemi-decusation (nasal fibres will cross, temporal will not)
location of the visual cortex
above and below the calcarine sulcus, extending to the occipital pole
our eyes are binocular. what does this mean
both of our eyes see the same thing
what is fixation point
point of visual acuity corresponding to the fovea. it where all quadrants of visual field meet
define scotoma
localised patch of blindness
define anopia and give examples of 2 types
the loss of one or more quadrants of the visual field
e. g. hemianopia= one HALF of the visual field is lost (both of upper and lower on that half are lost)
e. g. quadrantanopia= one QUADRANT of the visual field is lost only
define homonymous
visual field losses are on same side for both eyes
define heteronymous
visual field losses are on different sides for both eyes
3 examples of visual defects
monocular blindness (completely blind in ONE eye)
bi-temporal hemianopia (outer half BOTH right and left visual field is missing)
homonymous hemianopia (visual field loss on same side of both eyes)
which region of the external ear is bony/cartilaginous
lateral 1/3= cartilaginous
medial 2/3= bony
tympanic membrane may be called the eardrum. what is its function
to separate the external and middle ear.
–> it is part of middle ear
middle ear is high risk space why?
- eustachian tube connects it to naso-pharynx= prone to infection
- connected to mastoid air cells= infection spread to middle cranial fossa
- inferior is the IJV= risk of thrombosis
- anterior is the internal carotid artery= risk of pulsatile tinnitus
- transversed by facial nerve and canal= infection spread to facial muscles
3 features of the auditory pathway
polysynpatic (many neurones/ synpases)
tonotopically organised
bilateral (recieve sound from both ears)
auditory centres in brainstem are…
cochlear nuclei
SUPERIOR olivary nuclei
inferior colliculus
MEDIAL geniculate nucleus
cell bodies of the cochlear nerve (CN8) are in the
spiral ganglion. will travel into the dorsal/ventral cochlear nuclei
where are low and high frequency sound recieved in cochlear and projected in the heschl’s gyrus
base= high
apex=low
low= antero-lateral part of heschl's gyrus high= postero-medial part of heschl's gyrus
secondary auditory areas
brocas- anterior of frontal, motor production of speech
wernickes - posterior of temporal, understanding of speech
