MCAT-PSY: Sensation and Perception

sensation/transduction

the conversion of physical, electromagnetic, auditory information from the environment to electrical signals in the nervous system

perception

the interpretation of electrical signals sent to the nervous system to make sense of their significance

distal stimuli

stimuli originating from outside the body

proximal stimuli

stimuli directly interacting with and affecting receptors

ganglia

collection of neuron cell bodies found outside CNS

photoreceptors

respond to electromagnetic waves in the visible spectrum

hair cells

respond to movement of fluid in the inner ear structures (hearing, rotational and linear acceleration

nociceptors

respond to painful or noxious stimuli (somatosensation)

thermoreceptors

respond to changes in temperature (thermosensation)

osmoreceptors

respond to the osmolarity of the blood (water homeostasis)

olfactory receptors

respond to volatile compounds (smell)

taste receptors

respond to dissolved compounds (taste)

threshold

the minimum amount of stimulus that renders a difference in perception

absolute threshold

the minimum of stimulus energy needed to activate a sensory system

never reaches CNS

subliminal perception

the perception of a stimulus below a given threshold

threshold of conscious perception

the minimum stimulus energy that reaches the CNS

discrimination testing

a participant is presented with a stimulus that varies slightly until they are able to detect a difference

difference threshold (just-noticeable difference)

the minimum difference in magnitude between two stimuli before one can perceive this difference

Weber’s law

that there is a constant ratio between the change in stimulus magnitude needed to produce a jnd and the magnitude of the original stimulus

accurate except for at the extremely high and low ends of ranges

signal detection theory

that the perception of stimuli can be affected by nonsensory factors like experiences, motives, and expectations

response bias

the tendency of subjects to systematically respond to a stimulus in a certain way due to nonsensory factors

catch trial

signal detection experiment, a signal is presented

noise trial

signal detection experiment, a signal is not presented

hit

signal detection experiment, the subject correctly perceives the signal

miss

signal detection experiment, the subject fails to perceive a given signal

false alarm

signal detection experiment, the subject perceives a signal when none was given

correct negative

signal detection experiment, the subject correctly identifies that no signal was given

sclera

a thick structural layer over most of the exposed portion of the eye, does not cover the front

choroidal vessels

one of two sets of blood vessels supplying the eye, intermingling between the sclera and retina

retinal vessels

one of two sets of blood vessels supplying the eye, within retina

retina

contains photoreceptors that transduce light into electrical information the brain processes

cornea

clear, domelike window in the front of the eye that gathers and focuses the incoming light

anterior chamber

in front of the iris

posterior chamber

between the iris and the lens

iris

the colored part of the eye

dilator pupillae

a muscle that opens the pupil under sympathetic stimulation

constrictor pupillae

a muscle that constricts the pupil under parasympathetic conditions

choroid

continuous with the iris

ciliary body

produces the aqueous humor that bathes the front part of the eye

canal of Schlemm

where the aqueous humor drains

lens

right behind iris and helps control refraction of incoming light

ciliary muscle

contracts under parasympathetic control, pulls on suspensory ligaments and changes the shape of the lens

accommodation

the changing of shape of the lens

retina

in the back of the eye, a screen of neural elements and blood vessels that convert incoming photons into electrical signals

part of CNS

duplexity/duplicity theory of vision

that the retina contains 2 photoreceptors for light-dark detection and color detection

cones

for color vision and to sense fine details

rods

for light and dark perception, contain rhodopsin

macula

the central section of the retina, high concentration of cones

fovea

the centermost point of the retina, contains only cones

bipolar cells

adjacent to rods and cones, highlights gradients between adjacent rods or cones

ganglion cells

adjacent to bipolar cells, group together to form the optic nerve