Chapter 2 - The Human Senses Flashcards
Absolute Threshold
the point at which energy from a stimulus becomes detectable
Difference Threshold
the minimum change in stimulus intensity needed for us to notice at least 50% of the time that a change has occurred
Weber’s Law
the magnitude of a just noticeable difference is proportional to the intensity of the original stimulus
Signal Detection Theory
the detection of a stimulus depends not only on the intensity of that stimulus, but also the physical and psychological state of the individual
Phasic (rapidly-adapting) Receptors
respond quickly and entirely to a stimulus, but stop responding even if the stimulus remains constant
Tonic (slowly-adapting) Receptors
respond gradually to a stimulus and provide a continuous signal for the entire duration of the stimulus
Exteroceptors
located close to the body’s surface and are specialized to detect external stimuli (tactile, gustatory, visual, olfactory, and auditory)
Interoceptors
located within internal organs and are specialized to detect sensory info concerning the body’s internal environment (BP, pH, gas conc.)
Proprioceptors
located in joints, muscles, tendons, and vestibular structures of the inner ear; detect specific movement and positioning required for spatial reasoning and balance
Top-down Processing
the use of previous knowledge and contextual information in pattern recognition (explains why it is easier to understand messy handwriting when reading a sentence rather than a single word)
Bottom-up Processing
perception begins with the stimulus itself, using bits and pieces of sensory information to generate a larger picture (data-driven processing–hearing a big, seeing bug, then swatting bug)
Monocular Cues
2D cues that one eye can detect, include perceptions based on relative size, interposition, texture, shading, and height
Binocular Cues
simultaneous input from both eyes and are more powerful interpreters of depth
Retinal Disparity (Binocular Disparity)
the difference in retinal images due to our eyes being 2.5 inches apart, so each eye receives slightly different info depending on its particular viewing angle
Convergence
shapes our perception of depth based on muscular feedback involved with eye rotation
Motion Parallax
explains why we perceive fast-moving objects to be closer than slow-moving objects
Phi Phenomenon
apparent motion caused by the rapid succession of stationary stimuli
Perceptual Constancy
the tendency to recognize familiar objects as having the same properties despite changes in their lighting, distance, or angle of perspective (top-down)
Color Constancy
allows recognition and perception of the color of an object as remaining relatively unchanged under different viewing or illumination conditions
Size Constancy
allows perception of an object’s true size despite its appearing to be larger or smaller, depending on changes in proximity
Shape Constancy
allows perception of an object’s true shape despite its being distorted by different viewing angles
Gestalt Principles
similarity (perceive similar stimuli to be a part of the same object, and to group them), proximity (perceive stimuli that are close to one another to be a part of the same object), continuity (affinity for spotting patterns and ability to differentiate between overlapping stimuli), and closure (mind’s inclination to recognize complete figures and fill in gaps, even if a pic is incomplete)
Cornea
transparent and protective membrane that functions as an outer lens, bending light to provide roughly 70% of the eye’s total focusing power
Pupil
opening of adjustable diameter that is regulated by surrounding contractile tissue (iris)
Iris
colored muscle that constricts or dilates to maintain a balance between visual acuity
Retina
multi-layered, light-sensitive tissue that lines inner surface of the eye (similar to biconvex lens, eye’s lens focuses an image onto the retina that is smaller, inverted, and left-right reversed compared to the viewed object)
Ciliary Muscles
suspensory ligaments holding the lens in place to apply adjustable increments of tension necessary for focus (focusing on distance = relax, causing ligaments to become taut to flatten the lens to increase focal distance)
Sclera
visible, white portion of eye, fibrous, protective layer that covers the eye and provides rigidity
Aqueous Humor
a gelatinous fluid that maintain the intraocular pressure of the eye, supplies nutrients, and removes debris
Vitreous Humor
gelatinous fluid found behind the lens, in the vitreous chamber, maintains eye’s shape and keeps retina in place by pressing it to the choroid
Choroid
a layer of connective tissue and blood vessels that nourishes the posterior structures of the eye
Extraocular Muscles
control gross eye movement and eyelid elevation
Amacrine Cells and Horizontal Cells
synapse across the other neurons to communicate laterally and coordinate sensory input
Bipolar Cells
relays inhibitory or excitatory responses to retinal ganglion cells
Retinal Ganglion Cells
exit retina via optic nerve and carry visual sensory info to the brain
Photoreceptor Cells
activated by light, a biochemical cascade results in decreased glutamate release to affect activity of bipolar cells
Blind Spot
axon of each retinal ganglion cell exits thru the same point (optic nerve) there’s simply no room for photoreceptors in this region
Fovea
an indentation at the center of the retina, which helps minimize distortion of light
Cones
color vision
Rods
peripheral vision, contrast and edge perception, and nighttime vision
Photopic Vision
caused by cones, occurs under conditions of high illumination and generated colored perceptions with high acuity
Trichromatic Theory of Color Vision
three types of cones, each with different spectral sensitivity–about 60% of cones are sensitive to red wavelengths, 30% to green, and 10% to blue; combos of these 3 colors of light can produce any color within the visible spectrum
Scotopic Vision
caused by rods, conditions of low light, cones do not activate reliably, less finely detailed vision
Rhodopsin
a pigment composed of opsin and retinal, absorbs incoming light, causing the chromophore retinal to change from the 11-cis form to the 11-trans form
Phosphodiesterase (PDE)
cyclic GMP-specific enzyme–each activated PDE will hydrolyze roughly 1000 cGMP molecules into GMP
Photopsin
main pigment in cones
On-center, Off-surround Ganglion Cells
fire more strongly when light strikes the center of their receptive fields, but not surrounds
Off-center, On-surround Ganglion Cells
fire more strongly when light strikes surrounds of their receptive fields, but not center
Retina-geniculate-striate Pathway
conducts retinal signals through the lateral geniculate nuclei (LGN) of the thalamus to the primary visual cortex
Primary Visual Cortex
located in posterior occipital lobe
Temporal Hemiretina
outer portion of retina, receives visual signals from the opposite visual field and sends them ipsilaterally to the primary visual cortex
Nasal Hemiretina
inner portion of retina, receives visual signals from its like-sided visual field and sends them contralaterally to the opposite primary visual cortex via the optic chiasm
Parvocellular Pathway
a pathway of the retina-geniculate-striate pathway, about 80% of cells travel through the four top layers to form this pathway
Magnocellular Pathway
includes remaining 20% of retinal ganglion cells that travel through bottom two layers of LGN
Feature Detection
ability to identify the color, form, depth, and movement of an object (result of parvo/magnocellular pathways)
Parallel Processing
brain’s ability to process different components of incoming stimuli simultaneously
Pinna
visible, curved piece of cartilage that catches sound on outer ear
Tympanic Membrane
eardrum, vibrates small bones known as ossicles
Malleus
hammer, detects vibrations and relays them to the incus
Incus
anvil, vibrates the stapes
Stapes
stirrup shaped bone, amplifies sound vibrations and protects from loud, damaging noises
Stapedius Muscle
triggered by prolonged exposure to loud sound, this muscle connects the eardrum and small bones, to contract and pull the tympanic membrane and ossicles in opposite directions creating rigidity to dampen vibrations
Oval Window
thin membrane connecting the middle ear to inner ear, causing it to vibrate the fluid within the cochlea
Round Window
relieves pressure as the oval window moves in and out, moves in the opposite direction
Cochlea
long, snail-shaped tube that contains an internal membrane called the organ of Corti
Organ of Corti
partitions the cochlea into a longer, narrower tube and is composed of two membranes
Basilar Membrane
contains hair cells that convert pressure differences into neural signals that are sent to the brain via the auditory nerve
Hair Bundle
exposed portion of the hair cells, composed of stereocilia
Stereocilia
progressively increase in length toward one end; tallest one is called the kinocilium
Tip Links
spring-like filaments connect tips of stereocilia to one another and are attached to gates of K+ channels
Endolymph
unique fluid with an unusually high potassium conc. and unusually low sodium conc.
Cochlear Nuclei
collections of neurons in the hindbrain where axons of each auditory nerve (one exiting from each cochlea) synapse ipsilaterally
Auditory Processing
from the cochlear nuclei, info may decussate at the trapezoid bodies or travel ipsilaterally to synapse at the superior olivary complex –> axons from the olivary neurons travel thru the lateral lemniscus and synapse to neurons in the inferior colliculi of the tectum –> info travels to the medial geniculate nuclei of the thalamus –> relays info to the primary audio cortex for processing
Heschl’s Gyrus
shallow region of the Sylvian fissure where low-frequency sounds project
Utricle
located in the horizontal plane and is sensitive to horizontal movement
Saccule
in the vertical plane, sensitive to vertical movement (acceleration against normal gravity)
Meissner’s Corpuscles & Pacinian Corpuscles
fast-adapting receptors, fire immediately to inform you that something has hit your hand, but they stop firing just as quickly
Merkel’s Discs & Ruffini Endings
slow-adapting receptors, slowly and continuously fire to inform you that something is still in your hand–still desensitize under prolonged exposure
Free Nerve Endings
simply exposed dendrites that are particularly sensitive to temperature and pain
Transient Receptor Potential (TRP) Receptors
embedded in membrane of thermoreceptors, temp causes conformational change that allows sodium and calcium to flow into the cell
Anterolateral System
generally carries info regarding temp and pain
Dorsal-column Medial-Lemniscus System
carries info regarding pressure, stretch, vibration, and proprioception
Primary Olfactory Cortex
in the medial temporal lobes, info about smell is not relayed thru the thalamus before reaching the cortex
Ion Channels
mediate salty (Na+) and sour (H+) tastes
G-protein-linked Receptors
mediate sweet, bitter, and umami tastes
