Visual Flashcards
Where is sensation of vision located?
Occipital lobe
Visible wavelengths
400-750nm
what is the fibrous capsule composed of
the sclera (whites of eyes) and the cornea
what does the cornea do
refract light onto the retina
What/where is the aqueous humor and what is the purpose of it
In front of the lens, under the cornea is salty water to maintain interocular eye pressure
Constriction of pupil
Improved depth focus
Convergence of eyes
Objects remain in focus on corresponding parts of the two retina (go cross eyed)
Vitreous humor
jelly like main part of eye, maintains interocular pressure
what does the retina do?
Receives light and turns it into neural signals, is an outgrowth of the thalamus
Fovea
Has highest resolution of vision and densest number of CONE photoreceptors
Optic nerve (cranial nerve II)
where ganglia cells from the retina leave the retina and goes to the brain
What is the Choroid and pigment epithelium
Choroid: vascular layer of eye between sclera and retina
Pigment epithelium: deepest layer of retina, black to absorb light so theres no refraction
Cataract
Cells die in the lens and becomes opaque
Accomodation (in near response)
contraction/relaxation of ciliary muscle and loss of tension on zonular fibres to alter lens shape (more spherical) and change refractive power
Constriction of pupil
Improved depth focus
How does the neural component of eye work?
converts light energy into patterned changes of membrane potential that the brain can decode to create visual perceptions
Rods detect what light (dark or bright)
detect light in low light (not colour sensitive)
Cones
detect colours in bright light - have S, M and L receptors (short medium long)
Photopigments
- hint (opsin + vit A)
Makes photoreceptors light sensitive made of an opsin and retinal
Rods: Rhodopsin
Cones: Photopsin
Rod phototransduction (in the dark)
In absense of light, 11-cis retinal is non-activated, intracellular cGMP levels are high and open cGMP-gated channels allowing influx of Na, depolarising the cell and glutamate is constantly released onto bipolar cells
Cone phototransduction
In light, retinal changes to active all-trans isoform which activates transducin which tells cGMP phosphodiesterase to break down cGMP = causing closing of cGMP gated channels and hyperpolarising the cell reducing glutamate release
Cone phototransduction (in the dark)
In absense of light, 11-cis retinal is non-activated, intracellular cGMP levels are high and open cGMP-gated channels allowing influx of Na, depolarising the cell and glutamate is constantly released onto bipolar cells
Cone phototransduction (in the light)
In light, retinal changes to active all-trans isoform which activates transducin which cGMP phosphodiesterase to break down cGMP = causing closing of cGMP gated channels and hyperpolarising the cell due to K+ leakage, reducing glutamate release. This acts as a signal that light is present.
Colour blindness can be i……… or a…………
Inheirited (congenital) or aquired (due to disease and damage to the optic nerve or retina)
Colour blindness can be i……… or a…………
Inherited (congenital) or acquired (due to disease and damage to the optic nerve or retina)
Diseases that damage the optic nerve or retina
Glaucoma: increase in pressure in aqueous humor
Diabetes
Alzheimer’s or Parkinson’s
Visual pathway (5 locations) - R, SC, LGN, SN, Pr
Retinal ganglion cell axons leave retina at the optic nerve and send axons to parts of brain to the -
Superior colliculus: coordinates rapid movement and tells you to react to visual stimuli
Lateral geniculate nucleus of thalamus: decides what information is worthy to be processed and is then send to the occipital lobe
Suprachiasmatic nucleus: involved in circadian rhythms
Pretectum: coordinates pupillary light reflex
Visual pathway (5 locations) - R, SC, LGN, SN, Pr
Retinal ganglion cell axons leave retina at the optic nerve and send axons to parts of brain to the: Superior colliculus Lateral geniculate nucleus of thalamus Suprachiasmatic nucleus Pretectum
Superior colliculus
coordinates rapid movement and tells you to react to visual stimuli
Lateral geniculate nucleus of thalamus
decides what information is worthy to be processed and is then send to the occipital lobe
Suprachiasmatic nucleus
Involved in circadian rhythms
Pretectum
coordinates pupillary light reflex
What is the blind spot
where the axons from the retina leave and head to parts of the brain (optic nerve/optic disc)
