Studied by 2 peoplebipolar cells
cells in the retina which transmit impulses from photoreceptor cells to ganglion cells
blind spot
point at the back of the eye where optic nerve exits
cone cell
photoreceptor cell in retina that is responsible for colour vision
fovea
centre area of the macula that contains only cone cells
ganglion cells
cells in retina that transmit impulses from bipolar cells to brain
generator potential
depolarisation of receptor plasma membrane which reaches threshold and initiates action potential
infraction
tissue death caused by lack of blood supply
iodopsins
Photoreceptor proteins in cone cells
Macula
area of retina with most cone cells
rhodopsin
Photoreceptor protein in rod cells
rod cells
light sensitive photoreceptor cell in retina that functions in low light
transducers
sensory receptors that convert light to electrical energy
sclera
tough white outer layer containing collagen that protects the eye
choroid layer
layer behind retina which absorbs light, rich blood supply
retina
innermost layer containing photoreceptor cells
fovea centralis
area of retina with high concentration of cone cells for best visual acuity
optic nerve
bundle of neurones carrying impulses from eye to brain
blind spot
point where optic nerve exits and there is no photoreceptor cells
conjunctiva
protective layer at at front of eye kept moist by film of fluid
iris
coloured tissue at front of eye which controls light entering pupil by smooth muscle
pupil
black hole in centre which lets light in
cornea
clear part of sclera at front that covers iris and pupil which helps focus light
lens
stacks of long, narrow, transparent cells which focus light
ciliary body
muscle which holds lens and alters its shape
suspensory ligament
inelastic ligaments that attach ciliary muscle to lens
vitreous humour
gelatinous fluid within eye which exerts pressure outwards to maintain eye shape
aqueous humour
watery fluid in front of lens which helps maintain shape
conjunctivitis
inflammation or infection of a part of the eye where the blood vessels become dilated or haemorrhage appearing pink or red
dim light
more light let in, radial muscles contract, circular muscles relax, sympathetic nervous system
bright light
reduces light entering, radial muscle relax, circular muscle contract, parasympathetic nervous system
refracting surfaces of eye
cornea, front and back of lens
distant object
circular ciliary muscles relax, suspensory ligaments taut, lens pulled thin, less refraction of light
near object
circular ciliary muscles contact, suspensory ligaments slackened, lens bulge, more refraction of light m
myopia
elongated eyeball, light from distance focus in front of retina, treated with concave lens, laser eye surgery, or lens implant
types of cone cells
cells sensitive to red, blue or green
rod cell
longer photoreceptor cell
order of retina cells
optic nerve axons, ganglion cells, bipolar cells, photoreceptor cells, pigment epithelium
retinal
absorbs a photon of light and is converted to trans-isomer from cis-isomer. activates opsin
opsin
protein in rhodopsin with retinal
bleaching
when rhodopsin spits due to retinal changing isomers, reversed by re synthesis with ATP
ATP produced for re synthesis of rhodopsin
many mitochondria in inner segment of rod cells
vitamin A
vitamin needed to to re synthesise retinal into rhodopsin
iodopsin
photosynthesis pigment in cone cells which eolith absorbs red, green, or blue light
s cone
short wave light blue light - 420nm
m cone
medium wavelength green light - 543nm
l cone
long wavelength red light - 564nm
bipolar cells
synapse with many rod cells or single cone cell, and ganglion cell on other
summate
when many rod cells combine to depolarise bipolar neurone
glutamate
inhibitory neurotransmitter which causes the adjacent bipolar neurone to become hyper polarised
glutamate
causes ganglion neurone to become depolarised creating generator potential
visual acuity, colour vision, pupil response
3 aspects of eye tests
every 2 years
routine eye test carried out
snellen chart
letters chart, big to small, viewed at 6m, one eye covered
20/20 visual acuity
ability to ready letters 1cm high at 6m
near vision test
reading card with different size blocks of text at 30cm
presbyopia
near vision loss. lens is less flexible as older (40+) so less able to focus near objects
colour blindness
absence of one or more types of cone, recessive sex linked condition affecting makes more
protanopia
absence of red cone cells
deuteranopia
absence of defect in green cone cells
Ishihara colour vision test
individuals with colour blindness don’t see numbers, different colour combinations
Farnsworth-munsell 100 hue test
caps sorted into hue order, red, green, blue and yellow
optical coherence tomography
OCT, non invasive, beam of near infra red light, detects reflected light, scattered removed with interferometry, 3d image of retina, map and measure thickness
neurones die
loss of synaptic connections at about age 20
brain volume and mass
brain decrease by 10% at 90, frontal lobe and hippocampus effected most
thinner cortex
thins from age 20, due to loss of synaptic connections
white matter
decreases with age, leading to reduced speed of cognitive processing like memory, attention, action, problem solving, and decision making
ventricles
enlargement with age, more significant with dementia
neurotransmitters
effects memory due to less synthesis of receptor proteins and…
onset of dementia
age related memory loss is temper lapses of memory however severe disruptive loss indicates…
slow age related memory loss
regular exercise, manage stress, crosswords
worsen age related memory loss
smoking and alcohol
effect of ageing on reaction times
simple involuntary reflex, different ages, unpaired t test
presbycusis
age related hearing los, gradual from 18 years, loss of sensitive share cells in cochlea and neurone in auditory nerve
high frequencies
frequencies most effected by age related hearing loss
range of normal speech
autograph carried out between 250 and 8000Hz
normal hearing level
up to 25dB
glaucoma
tunnel vision, optic nerve damage, increased eye pressure as aqueous humour doesn’t drain, eye drops, laser, medication, or surgery
chronic open angle
drainage channels slowly come blocked, reduced visual field
acute closed angle
less common, rapid onset, pressure in eye pushes edge of iris against cornea blocking drainage channels
age related macular degeneration
ARMD, loss of central vision due to degeneration of macula, dry- debris from pigments not broken down, retina detaches, wet- blood vessels grow, laser treatment, strong glasses
cateracts
clouding of lens and loss of elasticity, blurred vision, worse in low light, denaturation and aggregation of lens proteins, age related, stronger glasses and brighter lights, replacement lens
alzheimers
degenerative disease of nerve system effecting frontal and temporal lobes
early Alzheimers
minor memory loss eg names and location of objects
suffers aware of memory loss
long term memory intact
mid-stage Alzheimers
personality changes, physical problems
dependant on others for care
no longer aware of memory loss
impaired long term memory
late stage Alzheimers
deterioration of personality
loss of control over body functions
total dependency on others
speech severely effected
inability to swallow and lead to death
multifactorial
disease with many factors contributing to it eg Alzheimers, effected by age and family history
abnormal break down of protein
B amyloid proteins are produced from myelin sheath which accumulate and form plaques around neurones causing them to degenerate and less neurotransmitter produced.
tau proteins
proteins which normally stabilise microtubules in cytoskeleton, defective ones aggregates forming neurofibrillary tangles in neurones. microtubules disintegrates and transport system collapse, less neurotransmitter, nerve dies
cholinergic
reduction in acetylcholine levels, most treatments based on this
amyloid
location of even for protein precursor on chromosome 21, links it to down syndrome. maybe derrivative called ADDLs that cause damage
tau
abnormalities in proteins cause neurofibrillary tangles interfering with microtubules and intracellular transport in neurones
acetylcholine inhibitors
use to prevent breakdown of acetylcholine to treat Alzheimers
carers activities
help with eating, washing, dressing, going to toilet
carers difficulties
financial cost, ability to work, distress, patients legal maters
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