Eyeball Physiology Flashcards
What is a wavelength?
Peak to peak
What is a focal point?
The point at which rays or waves converge after refraction
What is far vision?
Normal vision
What does refraction mean?
Bending light
What is near vision?
Looking at something up close
The closest point we can see something up close clearly
What are the 3 parts to near vision?
Accommodation, constriction of pupil (parasympathetic) and convergence of eyeball
What are the inner segments?
Connecting cilium that connects to the cell body (in the neural layer)
What is near vision accommodation?
Process that increases the refractory power of the lens
What is convergence of the eyeballs?
Crossing your eyes
What controls the ciliary bodies?
Parasympathetic fibers and oculomotor nerves
What is constriction of the pupils?
The sphincter pupillae muscles of the iris enhance the effect of accommodation
What are the accommodation steps?
The ciliary muscles contract, pulling the ciliary body toward the pupil and inward, releasing tension in the ciliary zonule
What is nearsightedness
Can’t see far away
What is myopia?
Nearsightedness and eye is too long
What are the outer segments?
The receptive regions of rods and cones
What are the 2 vision defects?
Myopia and hyperopia
What is farsightedness?
Can’t see close up
What is hyperopia?
Farsightedness and eye is too small
What is a visual pigment (photopigment)?
They trap light and change shape
What happens to the lens when ciliary muscles relax?
Gets flattened
What happens to the lens when ciliary muscles constrict?
Gets rounded (fat)
The fatter the lens, the more….
strentgh
What is retinal?
A light-absorbing molecule
What are the parts of a visual pigment?
Retinal and opsin
What is an opsin?
A protein
Rods vs cones: noncolor visions
Rods
Rods vs cones: Color vision
Cones
Rods vs cones: High sensitivity
Rods
Rods vs cones: Low sensitivity
Cones
Rods vs cones: Mostly in central retina
Cones
Rods vs cones: Mostly in peripheral retina
Rods
Retinal and opsin combine together and form…
4 types of visual pigments
Retinal is related to vitamin…
A
Step 1 activation bleaching of pigment:
Retinal (cis-retinal) combined with opsin = forms rhodopsin
Step 2 activation bleaching of pigment:
Light absorption by rhodopsin triggers a rapid series of steps in which retinal changes from cis to trans and releases opsin
Step 3 activation bleaching of pigment:
Retinal changes from trans back to cis
Step 1 in the dark: cGMP-gated channels….
open. Photoreceptor depolarizes
Step 2 in the dark: Voltage gated calcium channels _____ in synaptic terminals
open
Step 6 in the dark: Does an action potential occur?
No
Step 3 in the dark: Neurotransmitter is…
released
Step 5 in the dark: Hyperpolarization _______ voltage-gated calcium channels, ______ neurotransmitter release
closes, inhibiting
Step 4 in the dark: Neurotransmitter causes __________ in bipolar cell
hyperpolarization
Step 1in the light: cGMP-gated channels….
close, photoreceptor hyperpolarizes
Step 2 in the light: Voltage gated calcium channels _____ in synaptic terminals
close
Step 3 in the light: Neurotransmitter is…
released
Step 4 in the light: Bipolar cells…
depolarizes
Step 6 in the light: Does an action potential occur?
Yes
Step 5 in the light: Depolarization _______ voltage-gated calcium channels, neurotransmitter is _______
opens, released
What is light adapatation?
Moving from darkness to bright light - the sensitivity of the retina is still “set” for dim light
What is dark adaptation?
Opposite of light adaptation: Cones stop functioning in low-intensity light
The bright light bleached our rod pigments and the rods are still turned off
Order of visual pathways:
Optic nerve, crosses in optic chiasma, optic tract, thalamus, primary visual cortex (occipital), association areas, midbrain (eye control) and hypothalamus (circadian rhythm: sleep-wake cycle)
