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120 Cards in this Set

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  • Back
  • 3rd side (hint)
sensory receptors
detect & respond to a specific stimulus
-act as transducers - convert stimulus energy into changes in membrane potential
-sensory information is communicated via action potentials carried by sensory neurons
monitor specific conditions within body or in external environment:
arriving information is called a sensation
awareness of a sensation is a perception
Each receptor responds best to ______ of stimulus.
Each receptor responds best to a specific type of stimulus.
conversion of one form of energy into another
arriving information
awareness of a sensation
general senses
pain, temperature, touch, pressure, vibration
special senses
olfaction (smell), vision (sight), gustation (taste), equilibrium (balance), and hearing
located in specific sense organs → structurally more complex
general senses receptors
throughout body, relatively simple structure; most cell processes (dendrites) that monitor conditions in body & environment
smaller receptive field =
more precise location
What are the classes of sensory receptors?
photoreceptors, mechanoreceptors, chemoreceptors, thermoreceptors, nociceptors
touch, pressure, stretch, vibration, sound, acceleration
use mechanically gated ion channels
monitor chemicals (taste, olfaction, pH O₂)
use chemically gated ion channels (ligand-gated)
warm, cold
Sensory receptors produce _______ (depolarization or hyperpolarization) in response to sensory stimuli
Sensory receptors produce graded receptor potentials (depolarization or hyperpolarization) in response to sensory stimuli
-caused by opening/closing of ion channels
greater the stimulus = greater the change in membrane potential

sensory receptors can be:
modified nerve endings or separate sensory cells
What is an example of modified nerve endings
touch receptors in skin
What is an example of separate sensory cell
photoreceptors in the eye
sensory unit
1 sensory unit + all sensory receptors associated with it
-each sensory neuron is associated with one type of receptor
receptive field
area of body supplied by 1 sensory neuron
- smaller receptive fields results in greater acuity (e.g. two point discrimination threshold)
tonic receptors
non-adapting or slowly adapting
fairly constant response to sustained stimulus (e.g. muscle stretch receptors)
phasic receptors
rapidly adapting
respond to initial change in stimulus, then decrease response (e.g. olfactory receptors)
Sensory Pathways to CNS
First Order Neuron
sensory neuron (receptor) delivers sensation to CNS cell body located in dorsal root ganglion
Second order neuron
axon of sensory neuron synapses on interneuron in CNS; from spinal cord/brainstem to thalamus
Third order neuron
if sensation is to reach our "awareness," the second-order neuron synapses on a third-order neuron in the thalamus and thalamus relays info to the cerebral cortex for "perception"
Third order neuron
thalamus relays info to the cerebral cortex for "perception"
somatosensory cortex
(perception of somatic sensations) parietal lobe (postcentral gyrus)
visual cortex
(vision) occipital lobe
auditory cortex
(sound) temporal lobe
olfactory cortex
(smell) temporal lobe
gustatory cortex
(taste) parietal lobe
3 layers (tunics) of eye
fibrous, vascular, sensory
fibrous tunic
forms outermost coat of eye, composed of: opaque sclera and clear cornea
vascular tunic
three regions:
choroid, ciliary body, iris
2 smooth muscle layers
sensory tunic
neural tissue with photoreceptors (cells that detect light waves)
Internal cavities filled with ______.
Internal cavities filled with ______.
(vitreous humor and aqueous humor)
vitreous humor
posterior cavity (clear gel) helps maintain shape
aqueous humor
anterior cavity (clear fluid) nourishment
biconvex, transparent, flexible, avascular structure
fovea centralis
region of retina where image focuses
highest density of cones (no rods)
optic disc
"blind spot" exit for optic nerve → no photoreceptors
Visual pathway
photoreceptors → bipolar cells → ganglion cells → optic nerve → crosses at optic chiasm → optic tracts → thalamus → visual cortex
6 extrinsic eye muscles →
allow eyes to follow a moving object while maintaining image on fovea centralis
visual acuity and astigmatism
light rays → bend (refraction) as they pass through convex cornea & lens
• passing from air to higher density structures (pass through slower)
• cornea is fixed; shape of lens is adjustable
concave and convex
surfaces diverge light waves
surfaces converge light waves to a focal point
• normal eye has good visual acuity (sharpness of vision)
• incoming light is sharply focused on fovea centralist of retina
• lens inverts image on retina
∙ left side of visual field → projected only right side of retina
∙ upper portion of field → projected downward
(nearsightedness) eyes are too long, light rays focus in front of retina
• individuals can see near; not far
• corrected with a concave lens
• tested for with Snellen chart
snellen eye chart
tests for myopia
normal vision - person can read to line marked 20/20
20/40 vision - individual must stand 20 ft from line that normal person can see at 40ft
(farsightedness) eye is too short light rays focus behind retina
• individuals can see far; not near
• corrected with a convex lens
visual defect produced by abnormal curvature of cornea or lens or irregularity on their surface
• vision is distorted & blurred
• corrected with uneven lens
• tested with an astigmatism chart
ability of eye to focus on objects at different distances
lens is flattened for distant vision →
ciliary muscles are relaxed & suspensory ligaments are taut

no PNS stimulation
lens is more spherical for close-up vision →
ciliary muscles are contracted & suspensory ligaments are relaxed

PNS stimulation
("old eyes") ability to lose focus on close objects decrease with age
• decline in elasticity of lens
• tested by measuring the closest point at which an individual can focus clearly
• e.g. 10 year old near pt of vision ~ 8cm; 70 year old ~ 100cm
6 extrinsic eye muscles →
allow eyes to follow a moving object while maintaining image on fovea centralis
• 3 cranial nerves control muscles
if tone of 1 muscle is weak or nerve is damaged → eye can drift slowly in 1 direction, followed by rapid movement in opposite direction to correct position
used to observer posterior portion of eye
macula lutea
"yellow spot"
• no rods
• fovea centralis - highest concentration of cones
• optic disc - blind spot
optic disc
blind spot
• area where axons of all ganglion cells gather to form optic nerve (no rods or cones)
• normally we are unaware of blind spot → brain "fills in" missing visual field
conversion of light energy into electrical signals
• carried out by rods and cones
• outer segment - molecules in disks that absorb light
• inner segment - nuclei & organelles
• synaptic terminal - storage & releases of chemical messengers
4 photoreceptor types
• 1 rod type
• 3 cone types
∙ blue cones
∙ red cones
∙ yellow cones
organic compounds that absorb light waves
•derivatives of rhodopsin
made of opsin (protein) bound to retinal (pigment) synthesized from vitamin A
retinal pigment
same in rods & cones
differs in each cone type
• opsin type within a cone determines which wavelength will be absorbed
retinal can assume various 3-D shapes (called isomers)
• When bound to opsin - retinal is kinked (11-cis-isomer)
• When pigment absorbs light - twists into different shape (all-trans isomer)
• Retinal = activated → ultimately causes AP to be transmitted down optic nerve
rhodopsin breaks down into retinal & opsin
• regeneration requires ATP & takes time

causes lingering visual impression
appears after "bleaching" of the visual pigment of affected receptors
Humans have _____ color vision
Humans have trichromatic color vision
• color vision → provided by stimulation of 3 cone types
can be cause by:
Genetic defect in photopigments (typically red and green)
• located on X chromosome
• more common in males (inherited by mother)
• females would have to inherit from mother and father
auditory system
responsible for hearing
vestibular system
responsible for balance or equilibrium
What are the two sensory systems?
auditory system and vestibular system
Both sensory systems (auditory and vestibular) rely on ___ to detect movement of fluid within the cavities of the ear
Both sensory systems (auditory and vestibular) rely on hair cells (mechanoreceptors) to detect movement of fluid within the cavities of the ear
-causes a receptor potential → afferent neuron → CNS
Hair cells in the ___ detect vibration produced by sound waves
Hair cells in the cochlear detect vibration produced by sound waves
Hair cells in the ______ respond to acceleration (motion and gravity)
Hair cells in the vestibular system respond to acceleration (motion and gravity)
Tympanic membrane
• thin connective tissue membrane that vibrates in response to sound
• transfers sound energy to the middle ear ossicles
• boundary between outer and middle ears
What are components of the external ear?
tympanic membrane
What are components of the middle ear?
auditory tube, ear ossicles (malleus, incus, stapes), oval window, round window
Middle ear
small, air-filled cavity
flanked laterally by the eardrum; medically by the oval & round windows
Auditory (eustachian) tube
connects middle ear with pharynx (or throat)
• helps maintain normal pressure in middle ear
What are the ear ossicle?
malleus, incus, and stapes
Three ear ossicles
transmit vibratory motion of the eardrum to the oval window
oval window
thin membrane that separates air-filled middle ear from fluid filled inner ear
round window
thin membrane that separates air-filled middle ear from fluid filled inner ear
bony labyrinth
surrounds and protects membranous labyrinth
• channels worm way through temporal bone
bony labyrinth is subdivided into:
semicircular canals
within membranous labyrinth —> potassium-rich fluid
between bony and membranous labyrinth —> similar to extracellular fluid (high in sodium, low in potassium)
spiral bony tube, located withing temporal bone
cochlear duct
tube within cochlea, contains endolymph lies between 2 chambers:
vestibular duct and tympanic duct
vestibular duct
contains perilymph
tympanic duct
contains perilymph
vestibular membrane
separates vestibular duct & cochlear duct
basilar membrane
separates tympanic duct & cochlear duct
spiral organ
(organ of Corti) sensory organ for sound
• located on top of basilar membrane
• contains hair cells & overlying tectorial membrane
tectorial membrane
attached to inner wall of cochlear duct
hair cells
stereocilia tips embedded within tectorial membrane
Sounds and Mechanism of Hearing
sound -
consists of waves of pressure through air or water

Hair Cilia
tips embedded in tectorial membrane

Coding of Sound Intensity and Pitch in the Cochlea
pitch -
encoded based on which portion of the basilar membrane vibrates

(intensity) encoded by the frequency of action potentials
semicircular canals
detect rotational acceleration
• 3 canals oriented in perpendicular planes to detect 3-dimensional motion
2 components
utricle & saccule

gelatinous membrane, bends hair cells when fluid moves in semicircular ducts
Utricle and Saccule
"ear stones" attached to membrane, bend hair cells when head moves
detect forward & backward accleration
detect up and down linear acceleration
conduction deafness
middle ear damage (e.g. middle ear infection, ossification of bones)
sensory deafness
cochlea or vestibulocochlear damage (e.g. infections, prolonged exposure to loud sounds)
Tuning Fork Tests:
Rinne's Test and Weber's Test
Vibrations from tuning fork are transmitted through skull bones to fluid in cochlea
Weber's Test
tuning fork placed on midsagittal line
• sound seems louder in conduction deaf ear
∙ cochlear hair cells are stimulated but room noise is excluded
∙ can stimulate with cotton in ear
• sound is louder in normal ear in sensory deafness
Rinne's Test
tuning fork placed on mastoid process; when sound is gone → place near external ear
• if sound re-appears (=no damage to middle ear/conduction deafness)
• put cotton in ear for 2nd test to stimulate conduction deafness
Afferent impulses from vestibular apparatus:
• make us aware of our position in space
• affect efferent somatic motor nerves (e.g. voluntary extrinsic eye muscles)
vestibular nystagmus
involuntary eye oscillations produced by vestibular activity's affect on extrinsic eye muscles
test with swivel chair
note: after ~ 20 seconds of rotation →
fluid in semicircular canals has stabalized
• if abruptly stop → causes fluid to move again (activated response)