nervous sytem 2 Flashcards
24: tonotopic organisation
starts at cochlea and sends information about sound to the Brain
24: coding sound frequency - place code
auditory system keeping track of where info originated
24: coding sound frequency - time code
firing a.p in auditory nerve fibres which synchronise with peaks of sound wave form
24: auditory pathway - what does the auditory nerve connect to
connects cochlea to brain
24: first synapse in auditory pathway
cochlear nucleus
24: auditory pathway - midbrain auditory centre
inferior colliculus
24: auditory pathway - thalamic auditory nucleus
medial geniculate body
(major synaptic stations in the pathways for information reaching auditory areas of cerebral cortex.)
24: auditory pathway - temporal lobe
auditory cortex
24: sound localisation - vertical plank vs horizontal
vertical - interactions of sound on the pinna (outer ear)
horizontal - interaural (between ears) differences in sound wave timing and intensity
24: patients with little/ no cochlear function - activation (how?)
electrical activation of cochlear nerve fibres by electrode arrays in the cochlea
24: cochlear implant (bionic ear) - induction coil
transmits signals across scalp and skull to implanted receiver
24: cochlear implant (bionic ear) - microphone and processor
converts sound to electrical pulses
24: cochlear implant (bionic ear) - electrode array in cochlea
activates nerve fibres arranged in frequency (high to low)
25: eye - the cornea
refracts light to bring it into focus on the retina
25: eye - lens
- responsible for accommodation
- adjust refractive properties to ensure objects are in focus
25: eye - iris
- pigment determines eye colour
- muscles controlled by autonomic ns adjusts pupil diameter according to light levels + emotional signals
25: eye - pupil
opening in centre of iris allows light entry
25: eye - retina
layer at back of eye
e.g photoreceptors, bipolar cells, ganglion cells, nerve fibres
25: eye - what happens as object is brought near to the eye
light rays need to be bent more to keep object in focus
25: eye - focal length when lens is rounder
shorter focal length
25: eye - role of ciliary muscles (distant vision vs near)
distant - less flattened for distant vision
near - rounded
25: contraction of ciliary muscles
- allows Zonule of Zinn, to slacken
- lens expands
- lens more rounded
25: emmetropic eye
focus light from a distant object on to retina
25: myopia
short sighted
25: myopic eye
- too much focal power for its length
- lights rays converge infront of retina
- cannot focus on distant objects
25: hyperopia
long sighted
25: hyperopic eye
- too little focal power for its length
- light rays converge behind retina
- cannot focus on close objects
26: when its dark what do photoreceptors release
glutamate
26: retinal ganglion cells
give rise to optic nerve fibres
26: retinal processing: action of photoreceptors in response to light
- reduce neurotransmitter released
- excites or inhibits bipolar cells
26: retinal processing: where do a.p first appear
ganglion cells
26: off centre type vs on - light shone onto centre
off - inhibits ganglion cell
on - excites
26: off centre type vs on - light shone onto surround
- excites ganglion cell
- inhibits
26: organisation of cone ganglion cells
centre around organisation
26: 2 types of cone ganglion cell centre surround organisation
- red (l) - green (m)
- blue - yellow
26: here do fibres from nasal retina cross
cross at optic chiasm
26: left eye temporal and right eye nasal
- go to left LGN and cortex
- represent right visual field
26: right eye temporal and left eye nasal
- go to right LGN and cortex
- represent left visual field
26: lateral geniculate body
- left - found on righit hemisphere
- projections from eye kept separate in different layers
26: visual cortex
5 areas
V1 (primary visual cortex) to V5 (MT)
26: primary visual cortex
- more cortical area to centre of vision
- receives info from retinas
26: 2 processing streams in visual cortex
dorsal stream - action pathway
ventral stream recognition pathway
