Ch 2: Sensation and Perception Flashcards
sclera
thick structural layer covering the eye (the white of the eye). Dies not cover the cornea
Two sets of blood vessels that supply the eyes with nutrients
Choroidal vessels
Retinal Vessels
Retina
innermost layer of the eye, contains the photoreceptors that transduce light into electrical signals
anterior chamber of the eye
portion before (in front of) the iris
posterior portion of the eye
portion behind the iris
iris
the colored portion of the eye
composed of two muscles: the dilator pupillae and the constrictor pupillae
Dilator pupillae
dilates the iris of the eye
under sympathetic stimulation
Constrictor pupillae
constricts the pupil of the eye under parasympathetic stimulation
Ciliary Body
produces aqueous humor which drains into the canal of schlemm
accommodation (vision)
- the ciliary muscle, a component of the ciliary body, changes the shape of the lens by contracting and pulling on suspensory ligaments
- under parasympathetic control
Vitreous humor
transparent gel that supports the retina
duplexity or duplex theory of vision
stated that the retina contains two types of photoreceptors: those specialized for light and dark color detection and those specialized for color detection
Cones
- used of color vision and fine details
- absorb blue (short) green (medium) and red (long) light
Rods
- used to see black and white in low light situations
- use rhodopsin
fovea
- the center most point of the macula (central section of the retina)
- contains only cones
Bipolar cells
- connect rods and cones
- rods &cones –> BP Cells –> ganglion cells
- highlight gradients between adjacent rods and cones
Amacrine and Horizontal cell function
-important in edge detection as they increase contrast perception
Visual pathway
- enter the eye through the lens and pupil
- light from the nasal visual field projects onto the temporal side of the retina and vise versa
- nasal-side optical fibers cross at the optic chiasm but temporal optical fibers do not, meaning all information from the left visual field project into the right side of the brain and vise versa
- visual pathways are called optic tracts once they leave the chiasm
- info then moves to lateral geniculate nucleus (LGN) in the thalamus and the superior colliculus
- info moves to the visual cortex of the occipital lobe from here via radiations
Parallel Processing (feature detection)
- the ability to simultaneously analyze and combine information regarding color, shape, and motion
- these features can then be compared to our memories to determine what is being viewed
parvocellular cells
- able to detect shape
- high color spatial resolution, low temporal resolution
- can only work with stationary objects though because of their low temporal resolution
magnocellular cells
- detect motion of objects
- high temporal resolution, low spatial resolution meaning no rich detail, sometimes blurry
responsibilities of the ear
- hearing
- rotational and linear acceleration (vestibular sense)
pinna or auricle
the cartilaginous outer part of the ear
Pathway of sound waves into the ear
pinna–> external auditory canal –> tympanic membrane (eardrum) –> malleus –> incus –> stapes –> oval window
of cochlea –> vibrations in perilymph –> vibrations in endolymph –> organ of corti –> vestibulocochlear nerve –> CNS
tympanic membrane
eardrum
separates the outer and middle ear
vibrates in phase with incoming soundwaves causing transmission of the soundwave through the ossicles into the inner ear
Eustachian tube
connects the middle ear to the nasal cavity
helps equalize pressure between the middle ear and the environment
Composition of the inner ear
- Begins with the oval window to the cochlea and contains the cochlea, vestibule, and semilunar canals
- membranous labyrinth is filled with endolymph and surrounded by perilymph within the bony labyrinth
vestibule
portion of the bony labyrinth that contains the utricle and saccule which are responsible for balance and determining one’s orientation in 3D
Otoliths
used in the utricle and saccule
otoliths are attached to specialized hair cells and resist motion stimulating underlying hair cells and thus sending signals to the brain
semicircular canals
sense rotational acceleration
pathway in the CNS of auditory signals
vestibulocochlear nerve –> brainstem –> medial geniculate nucleus (MGN) of thalamus –> auditory complex in temporal lobe
difference between LGN and MGN?
LGN = Lateral geniculate nucleus; Light MGN= Medial geniculate nucleus: Music (sound)
vestibule
- contains the utricle and saccule
- sensitive to linear acceleration so they are part of the balancing apparatus and to determine one’s position in 3D space
otoliths
structures attached to hair cells in the utricle and saccule that resist motion, moving the modified hair cells which send signals to the brain
Semicircular Canals
- sensitive to rotational acceleration
- when the head rotates, endolymph in the canals resist motion bending the underlying hair cells
superior olive
structure of the brain that localizes sound
inferior colliculus
involved in the startle reflex and helps keep the eyes fixed on a point while the head is turned (vestibulo-ocular reflex)
How is a signal transduced at the organ of corti?
vibrations of the endolymph from the stapes hitting the oval window of the cochlea cause movement of the basilar membrane underlying the organ of corti. stereocilia attached to the hair cells begin to sway back and forth with the endolymph causing the opening of ion channels –> receptor potential.
place theory
the location of a hair cell on the basilar membrane determines the pitch perception when that hair cell is vibrated. This means that the cochlea is tonotopically organized (which hair cells vibrating tells brain pitch)
High pitches are perceived where in the cochlea? Low pitches?
High: close to the oval window
Low: nearer the apex away from the oval window
Olfactory pathway
chemical signals bind to chemoreceptors in the nasal epithelium –> chemoreceptors are activated upon binding causing them to send signals to the olfactory bulb –> relayed via olfactory tract to higher brain regions (including limbic system)
5 basic tastes
- sweet
- sour
- salty
- bitter
- unami (savory)
olfactory sensors are sensitive to
volatile or aerosolized chemicals
Chemoreceptors responsible for taste are sensitive to
disolved compounds
taste pathway into CNS
chemoreceptors on taste buds –> brainstem –> taste center in the thalamus –> higher-order regions of the brain
four modalities of somatosensation
pressure
vibration
pain
temperature
Receptors of somatosensation
pacinian corpuscles: deep pressure and vibration
meissner corpuscles: light touch
merkle cells (disks): respond to deep pressure and texture
Ruffini endings: strech
Free Nerve endings: pain and temperature
pathway to CNS for somatosensation
transduction at a receptor –> brainstem –> somatosensory cortex in the parietal lobe
two point threshold
minimum distance necessary between two points of stimulation on the skin such that the points will be perceived as two separate points
physiological zero
between 86 an 97F is normal temperature of the skin. If an object is warmer than this temp, we perceive it as warm and vice versa with cold
Kinesthetic Sense of Proprioception
the ability to tell where one’s body is in space. Receptores for proprioception are found mostly in muscles and joints, play critical roles in hand-eye coordination, balance, and mobility
Bottom-Up Processing
- Data driven processing
- object recognition by parallel processing and feature detection
- the brain combines individual sensory stimuli into a cohesive image before trying to determine what the object is
Top-Down Processing
- conceptually driven processing
- driven by memories and expectations
- allows us to ID objects without having to analyze their specific parts
Perceptual Organization
the ability to combine top-down and bottom-up processing along with all other sensory clues about an object to create a complete picture or idea
Depth Perception
-relies on monocular and binocular cues
monocular cues for depth perception
relative size of objects
partial obscuring of one object by another
convergence of parallel lines at a distance
lights and shadows
primary binocular cues for depth perception
slight differences in images projected onto the two retinas and the angle required between the two eyes to bring the object into focus
form of an object is determined by…
parallel processing
feature detection
Gestalt Principles (basic idea)
there are ways for the brain to infer missing parts of a picture when a picture is incomplete
images tend to be perceived as more stable, consistent, and simple than they actually are
Law of Proximity (gestalt)
objects that are close to one another tend to be perceived as a unit
Law of Similarity (Gestalt)
objects that are similar tend to be grouped together
Law of Good Continuation
elements that appear to follow in the same pathway tend to be grouped together
Subjective Contours
perceiving contours and, thus, shapes that are not actually present in the stimulus
Law of Closure
when a space is enclosed by a contour it tends to be perceived as a complete figure
Law of Prägnanz
perceptual organization will always be as regular, simple, and symmetric as possible
