Ch 2 review Flashcards
Pupil
opening at the front of the eye where light passes through
Iris
-colored part of the eye
-iris will constrict or dilate in order to let in more or less light
cornea
-transparent covering of the front of the eye
-accounts for ~80% of focus power
Lens
-light entering the eye is reversed, inverted, then focused onto the back of the eye
-focusing of near and distal vision
-~20% of focusing power
difference between cornea and lens
lens can change shape (accommodate) to adjust lights focus, while cornea can not change shape
ciliary muscles
change curvature of the lens
increase in curvature…
increase ability to bend light, which increases focusing power
near point
lens can no longer adjust in close objects
Myopia
-nearsightedness
-image is focused in front of the retina making it harder to see distant objects clearly
Vitreous humor
gel-like fluid that fills the center of the eye
retina
-located in the back of the eye
-organized in layers and networks of neurons that convert the energy from light waves into neural signals
photoreceptors
-visual receptor cells that are sensitive to light
-composed of opsin and retinal
Rods
-sensitivity to light contrasts
-specialized for low light environments
-become more sensitive in the dark
Cones
-much less
-sensitivity to color contrasts
-specialized for dealing with bright, colorful stimuli
Fovea
-small area near the center of the retina that is packed with cones and has no rods
-sharpest vision in this area
Blind spot
-region where optic nerve leave the eye
-no photoreceptors located here
Visual process in the brain
half the fibers from each retina travel and remain on that side of the brain and the other half cross at the optic chiasma and all fibers end up in the primary visual cortex
light energy from the eye travels to the
lateral geniculate nucleus in the thalamus where more neural processes take place
Dark adaptation
process of increasing sensitivity in the dark and adjusting to dim levels of illumination
Spectral sensitivity
-rods and cones are sensitive to different waves of light
-threshold for light is lowest in the middle of the spectrum
Trichromatic theory
-The human eye contains three types of color receptors (red, green, blue)
-when one or more not present, colorblindness occurs
The neuro
receive nerve impulses and release communications to stimulate neurons at the opposite end
dendrites
receive nerve impulses and pass the information to the soma where the signal integrates
soma
transmits integrated info along the axon that allows nerve impulses to pass
axon
passes nerve impulses toward the terminal buttons that allow stimulation of nearby glands, muscles, and other neurons
sensory neurons
carry nerve impulses away from sense receptors toward the nervous system
moto neurons
carry nerve impulses away from the nervous system toward muscles and glands
interneurons
relay nerve impulses between neurons
glial cells
-surround neurons to hold in place
-facilitate transmission of nerve impulses
-remove corrupted neurons
-protect brain from foreign substances
-produce myelin sheath
myelin sheath
insulating covor for axons
Action potentials
-nerve impulses transmit information by means of electrochemical signals
-excitatory or inhibitory
excitatory input
increase the likelihood of an action potential release
inhibitory input
decrease the likelihood of an action potential release
phenomenon of action potentials
all or nothing principle
absolute refractory period
no other action potential may pass through
relative refractory period
an action potential may pass but needs additional activation to get to the baseline
convergence
occurs when multiple signals synapse onto a single cell
do more rods or cones converge on a single ganglion cell
more rods
rods result in better
sensitivity but poor acuity
cones result in better
detail but low sensitivity
