Lecture 1: Special Senses - Vision

touch, pain, temperature

what stimuli does the general senses detect?

spinal or cranial nerves

where are axons of sensory neurons of general senses located?

cranial nerves

where are axons of special senses located?

taste, light, sound, head movement, and smell

what stimuli are detected with the special senses?

through the thalamus and then to primary cortex and association areas

where does special sense information travel?

oculomotor, trochlear, and abducens

what cranial nerves control the extrinsic eye muscles?

extrinsic eye muscles

produce precise, rapid movements

eyelid and eyelashes

protective purpose for the eye

lacrimal apparatus

produce/drain tears

fibrous, vascular, and neural

what are the three layers of the eyeball most superficial to deep?

sclera and cornea

what structures are in the fibrous layer of the eye?

sclera

the white of the eye

cornea

anterior portion of the fibrous layer that allows light to enter the eye; translucent and avascular

collagen

what fibers make up the sclera and cornea?

choroid, ciliary body, and iris

what structures make up the vascular layer of the eye?

choroid

rich blood vessel supply that contains melanocytes and makes up most of the vascular layer

ciliary body

smooth muscle that surrounds the lens and allows it to change shape

ora serrata

scalloped edge of the ciliary body

iris

pigmented portion of the eye that surrounds the pupil and contains smooth muscle that regulates the size of pupil

pupillary dialator muscle

contracts to make pupil larger

pupillary sphincter muscle

contracts to make the pupil smaller

retina

what structure makes up the neural layer of the eye?

2

how many layers does the retina have?

photoreceptors

what receptors are found in the deep layer of the retina?

rods

black and white, low light

cones

color vision, bright light

fovea centralis

where most cones are located

optic disc

where the optic nerve leaves the eyeball, causing a blindspot

lens

disc that focuses light on the retina — does 1/3 of focusing

aqueous humor

fills the anterior cavity of the eye and is secreted by the ciliary body

vitreous humor

fills the posterior cavity and has a gelatinous texture; helps to maintain shape of the eye can keep the retina in place

substance and angle

what degree and direction of refraction depend on?

concave surface

what type of surface will cause light rays to diverge and not focus?

convex surface

what type of surface will cause light rays to converge and focus on the focal point

convex

what surface does the eye have as light passes through the lens and cornea?

flattened

what is the shape of the lens when an object is far away?

emmetropia

the lens flattens for distant vision

round

what is the shape of the lens when an object is close?

accommodation

the lens “rounds up” for near vision

ciliary body relaxes, creating more tension on the suspensory ligaments

how does a lens flatten?

ciliary body contracts, causing less tension on the suspensory ligaments

how does a lens round?

ciliary body and suspensory ligaments

muscles in these two structures allow the lens to change shape

hyperopia

farsighted; eye is too short

convex lens

what lens corrects hyperopia?

myopia

nearsighted; eyeball is too long

concave lens

what lens corrects myopia?

hyperopia, myopia, and astigmatism

what are the three errors of refraction?

astigmatism

irregular curvature of the lens/cornea; rays of light do not refract uniformly and cause blurred vision

bipolar and retinal ganglion cells

cells in the retina that synapse with the photoreceptor

horizontal cells

form connections between photoreceptors and bipolar cells and modulate transmission to enhance visual contrast

amacrine cells

located along the dendrites of retinal ganglion cells where they respond to changes in light intensity and moving objects

high-acuity

what type of vision do cones create?

no

can cones respond in the dark?

low-acuity

what type of vision do rods produce?

signaling in cells of the retina in the dark

photoreceptor depolarizes and releases NT which inhibits the release of NT by bipolar cells, and an action potential isn’t generated by ganglion cell

signaling in the cells of the retina in the light

photoreceptor is hyperpolarized which doesn’t cause a release of NT, so the bipolar cell depolarizes and releases the NT causing an AP to fire in the ganglion cell

opposite lobe

in what occipital love is visual field information processed?

optic chiasma

where does some visual information cross over?

thalamus and then the primary visual cortex

where is visual information processed?