Chapter 12: the eye Flashcards
sense organs
carry messages about the external/ internal environment to the CNS
a stimulus is a source of energy…
converted from one form to another
sensory receptors
modified ends of sensory neurons that are activated by specific stimuli sensory receptors (pick up stimulus) --> sensation & perception @ brain
sensory adaptation & example
occurs when you have adjusted to a change in environment
eg wearing clothes
photo-receptors
eyes (rods & cones)
chemoreceptors
tounge (taste buds), nose (olfactory cells), carotid arteries & brain (blood pH)
mechanoreceptors
ear (inner ear stereocilia for balance, sound), proprioreceptors and touch (skin)
thermoreceptors
skin (heat & cold receptors)
iris
colored muscle regulation the amount of light entering eye
opening for light to go in = pupil
3 separate layers of the eye
sclera, choroid layer, retina
sclera
outermost layer (protective) covered by a cornea
- no blood vessels; gets O2 from dissolved tears & nutrients from the aqueous humor
- lack of O2 and nutrients = glaucoma
cornea
transparent tissue that refracts light toward pupil
covers sclera
3 parts of choroid layer
iris, lens, viterous humor
choroid layer
middle layer of eye that has pigments that prevent scattering by absorbing stray light
lens
focuses image on the retina by action of dorsal & ventral ciliary muscles
vitreous humor
cloudy, jelly-like material maintains eye shape and lets light through
retina
inner most layer
composed of 3 layer of cells:
1. light sensitive cells: rods & cones
2. bipolar cells: pass message from rods& cones to cells of optic nerve
3. optic nerve cells: ganglion cells
light conversion occurs at ____
the RETINA layer
rods vs cones
rods: used to view dim light
cones: used to identify color (red, blue, & green cones)
fovea centralis
which layer?
- closely packed with rods and cones @ center of the RETINA; most sensitive area of the eye
optic disk
ie blind spot
lack of rods & cones: where the optic nerve comes into contact with retina
accomodation
adjustments made to the lens & pupil to view near or far objects
Accommodation - focusing for close vision
- thickening lens shape by flexing ciliary muscles, allowing tendons to relax
- pupil constricts
- increased refraction
accommodation- focusing for distant vision
- lens becomes thin (muscles relax, tendons pull)
- pupil may also dilate to allow as much light as possible
- decreased refraction
cataracts
lens or cornea becomes clouded
astigmatism
abnormal curvature of cornea or surface of the lens
myopia
nearsightedness
- image is focused in front of the retina
hyperopia
farsightedness
image is focused beyond the retina (eyeball too small)
colorblindness
inherited condition; lacking certain cones (red, blue, or green)
afterimages
can be (+) - ex strobe light
or (-) ex red/ green cones
- caused by fatigue of a cone in an area of the retina
sequence of passage of energy (through eye, conversion, where it gets interpreted in brain)
cornea –> aqueous humor–> pupil –> lens–> vitreous humor–> passes the cells in retina layer –> strikes choroid layer (absorbs light & reflects energy to..) –> receptor cells of the retina: rods & cones (covert light to chemical energy) –> chemical signal leaves eye through optic nerve –> occipital lobe of cerebrum interprets vision
extrinsic muscles
allow your eye to turn
- conscious control (frontal lobe)
receptor cells of the retina
rods and cones
optic nerve cells
ganglion cells (in retina)
