3.5 Sensation modalities Flashcards
sensation versus perception
sensation - receiving information
perception - organizing, assimilating, and interpreting sensory input
2 types of sensory receptors
exteroceptor - respond to external stimuli
interoceptors - internal stimuli
mechanoreceptor
mechanical disturbances
- ex. Pacinian corpuscles - pressure sensors in the skin, 1 of 4 mechanoreceptors in the skin
- send graded potential changes
- ex. Auditory hair cell - detects sound wave vibrations
- autonomic mechanoreceptor -> detection of stretching of intestinal walls
chemoreceptor
ex. olfactory, gustatory
- chemoreceptors in the walls of carotid and aortic arteries detect pH, PCO2, PO2
nociceptor
pain receptors
- a kind of chemoreceptor, detects chemical signs of damage
- autonomic pain receptors are not clear, but give sensation of dull or aching pain
“referred pain”
when nociceptors cross paths with somatic afferents from the skin
thermoreceptors
autonomic and somatic
- cold-sensitive
- warm-sensitive
- thermal nociceptors
electromagnetic receptors
induced by electromagnetic waves
- rod and cone of the retina of the eye (photoreceptors)
sensory stimuli has 4 properties
- stimulus modality - type of receptor
- stimulus location - localized by overlapping receptive fields
- intensity - frequency of APs; dynamic range (or range of intensities) can be expanded by “range fractionation” - multiple groups of receptors with limited ranges to detect a wider range of stimuli
- duration
sensory stimulus — duration
tonic -> fires AP as long as stimulus continues; adaptation -> frequency of APs decreases as stimulus continues at same level; phasic receptors -> fire APs when the stimulus begins, but don’t communicate the duration of the stimulus
nerves are trained to respond to
CHANGING stimuli; see adaptation
exception: nociceptors
proprioceptors
awareness of the self - body position, the kinesthetic sense
ex. muscle spindle - mechanoreceptor - detects muscle stretch
ex. Golgi tendon organs - tension in tendons
joint capsule receptors - detect pressure, tension and movement in joints
five taste buds
- salty, sweet, bitter (basic), sour (acidic), umami (amino acids)
taste pore + taste hairs
taste is transmitted through cranial nerve to temporal lobe, not far from olfactory information
olfaction
located at roof of nasopharynx, airborne chemical that dissolve in mucus
- olfactory nerves project directly to olfactory bulbs of the brain (near temporal lobes, near limbic system)
smell as good and bad
good and bad smells are learned, based on experiences. there is no universally noxious smell – dependent on culture/upbringing
pheromones
used by insects to communicate (food, threats, mating). not well studied in humans
outer ear
- auricle/pinna (the shape of the ear - the “pinnacle” of the ear)
- external auditory canal
middle ear
tympanic membrane
- ossicles
- three bones:
1. malleus
2. incus
3. stapes
inner ear
cochlea
- semicircular canals
- utricle
- saccule
what controls balance
3 semicircular canals: utricle, saccule, ampullae
filled with endolymph and hair cells that detect motion
detect rotations acceleration of the held
innervated by afferent neurons which send balance information to the pons/cerebellum
detects linear balance and static equilibrium
round window
releases excess pressure; membrane-covered hole in the cochlea near the oval window
Eustachian tube
passageway to the back of the throat to middle ear, equalizes pressure
mechanism of ear
- sound waves enter external ear
- pass through auditory canal
- TM vibrates -> malleus -> incus -> stapes (amplification)
- stapes -> oval window -> pressure waves sent to perilymph and endolymph (fluids in the cochlea)
- pressure waves in endolymph cause vibration of the basilar membrane, which is covered with auditory receptor cells called hair cells (cilia from apical structures)
- hairs contact the tectorial membrane (roof)
- (movement of basilar membrane bends the hairs on tectorial membrane)
- the displacement of hair opens ion channels in the hair cells, which result in NT release and stimulation of bipolar auditory neurons
- dendrites from bipolar auditory afferent neurons are stimulated by NT, thus sound vibrations are converted into nerve impulses
air -> bone -> fluid
organ of Corti
- basilar membrane
- hair cells
- tectorial membrane
found in the cochlea
pitch
– different sets of neurons for different pitches
frequency -> depends on regions of the basilar membrane
thick and sturdy near the oval window; thin and floppy near the apex of cochlea
low frequency -> stimulate at farthest away, away from oval window
high-pitch -> near the oval window
loudness
the amplitude of vibration = more frequency APs
auditory cortex
located in temporal lobe, helps with stereophonic hearing
hearing is highly adaptive
we hear vocal frequencies, and variations in human voices
retina
detects light and sends APs to brain
passage of light
enters cornea (clear front of eye), which is refracted,
choroid
beneath the sclera (darkly-pigmented cells that absorb excess light), beneath this is retina
anatomy of eye (DRAW)
p. 65
anterior chamber
contains fluids called aqueous humor.
just behind the cornea, in front of the iris
iris
muscles control the diameter of the pupil
posterior chamber
behind the iris, in front of the lens, made of aqueous humor
lens
fine tunes the angle of incoming light, whose curvature is dictated by the ciliary muscle
vitreous chamber
contains vitreous humor
part of brain that receives visual input
occipital lobe (“Obama could see the future”)
Organization of retina (DRAW)
p. 86
optic disk
where the axons from ganglion cells converge, contains no photoreceptors
fovea centralis
focal point - contains only cones and provides extreme visual acuity
rods and cones
rods connect to posterior wall of retina
contain special proteins (opsin) that change tertiary structure upon absorbing light
synapse on bipolar cells
AT DARK: depolarization, they release NT glutamate onto the bipolar cells, which inhibits firing. “GLUTAMINE at NIGHT.”
AT LIGHT: upon absorption of light, the photoreceptor stops releasing glutamate on the bipolar cells, the bipolar cells can depolarize (removal of inhibition), causing depolarization of ganglion cells, creating AP along the axon of ganglion cell
opsin is bound to…
bound to one molecule of retinal, derived from vitamin A
at dark…then at light
rods and cones have several trans double bonds and 1 cis double bond retinal and opsin keep a sodium channel open. cell is depolarized.
with absorbing a single photon, the retinal is converted to all-trans for, closing the sodium channel and hyperpolarized
optic nerve
all axons of ganglion cells form the optic nerve
night vision
accomplished by rods, which are sensitive to motion and dim light, found in the periphery of the retina
cones
require abundant light, produce color and high-acuity vision, concentrated at the fovea
Cones - Color - aCuity
each cone makes a particular pigment which changes conformation when light of appropriate frequency strikes it
emmetropia
normal vision
how to correct myopia
nearsightedness, CONCAVE (diverging) lens can be used
how to correct hyperopia
farsightedness, CONVEX lens
presbyopia
inability to accommodate focus - occurs with aging
visual processing
parallel processing
feature-detection theory
vision is 30% of the processing
depth perception
binocular cues, retinal disparity, convergence
monocular cues
depth cues available to either eye alone
- relative size - sizes of similar objects
- interposition - subject on top of another
- relative clarity - fuzziness
- texture gradient - see poppies
- relative height - things on top are farther away
- relative motion - things closer to us move more
- linear perspective - convergence of lines as distance increases
- light/shadow - closer object reflect more light
retinal disparity
the difference between left and right eyes
Sensory modalities table (DRAW)
p. 73
