I. Sensory Receptors (beginning of stimulus reponse cycle/feedback loop/reflex arc)
2. Response is generation of electrical event (i.e., local receptor or generator potentials that eventually trigger AP along sensory neuron to CNS)
3. Adaptation--most sensations decrease with time, stimuli having progressively less affect on receptor
2. Stimulus detected
b. Thermoreceptors (e.g., temperature)
c. Photoreceptors (e.g., light)
d. Chemoreceptors (e.g., taste, smell, blood ph, blood gas levels)
e. Pain receptors or nociceptors (e.g., pain or damage) Dermatomes
2. Columnar epithelium which secretes mucus needed to dissolve and remove
chemical stimulus
2. Each chemical smelled must react with cellular chemical receptor for detection
3. Only major sense that does not pass thalamus
2. Taste buds
2. Nerves that supply tongue/throat
glossopharyngeal (IX) posterior 1/3
facial (VII) anterior 2/3 for sensory, relayed through thalamus
hypoglossal XII
vagus X for motor
2. Lacrimal gland for lubrication/bacteriocide
3. Conjunctiva--mucus membrane over cornea
2. Layers
2) Cornea--transparent so light passes through
avascular so easily transplanted and not rejected
b) absorbs excessive light
3) Iris--colored portion seen through cornea--controls amount of light passing to retina
4) Pupil--hole in anterior portion of vascular tunic
2) Bipolar neurons are stimulated by photoreceptors
3) Photoreceptors transduce light to graded potentials (form image)
(b) Cone photoreceptors
color, highlight vision
high acuity = sharpness of vision
macula lutea--abundant cones in center of retina
Diagram the pathway for light, the site of photoreception,
and then the pathway for action potentials to get to the visual cortex in occipital
lobe.
b. Convergence--eyes rotated medially to focus on single object from far to near
c. Depth perception (binocular vision gives you depth perception)
| dark adaptation | if [rhodopsin] is large, vision is light sensitive (dark adaptated) |
| light adaptation | if [rhodopsin] is small (i.e., after bright light) vision is insensitive, e.g., can't see in dark room after bright light |
b. Cones
photopsin (similar to rhodopsin)
3 types (blue, green, red) to make all colors
b. external auditory canal
c. Tympanic membrane (ear drum)
b. Eustachian tubes--allows for equalizing pressure between atmosphere &
middle ear
2. Semicircular canals (equilibrium)
3. Cochlea (contains organ of hearing)
b. Cross section of cochlea
scala media ( or cochlear duct) divided from main part of scala vestibuli
by vestibular membrane
filled with endolymph fluid and houses hearing organ = organ of Corti
2. Physiology of hearing
| a. Sound waves (air compression) collected by pinna and directed through ear canal |
| b. Tympanic membrane moves to compressions &
decompressions converting sound waves to vibrations
c. Ossicle bones (malleus, incus, stapes) vibrate relative to membrane thereby transmitting vibrations to outer membrane of scala vestibul d. outer membrane of scala vestibuli vibrates relative to ossicle bones thereby transmitting vibrations to Perilymph Fluid in scala vestibuli e. Perilymph Fluid in scala vestibuli vibrates relative to outer membrane of scala vestibuli thereby transmitting vibrations to vestibular membrane f. vestibular membrane vibrates relative to perilymph thereby transmitting vibrations to endolymph fluid in scala media g. Endolympyh fluid in scala media vibrates relative to vestibular membrane thereby transmitting vibrations to tectorial membrane h. Fluid vibrations cause tectorial membrane to mechanically stimulte
hearing hair cells |
. Different areas of organ/Corti sense different frequencies |