8.3 Taste and Smell Flashcards
where do substances need to be to be able to taste and smell it
taste: substanced dissolved in saliva
Smell: substances dissolved in fluids of the nasal membranes
what type of cells are olfactory receptor cells
- bipolar neuron
- olfactory bulb anatomy
-
location of olfactory receptors
- odorant must be dissolved in the mucus layer, odorant receptors cillia in mucus membrane
describe the olfactory transduction process
- odor-causing chemicalbinds to a receptor -> initiates a G-protein mechanism, using cAMP as a second messenger
- cAMP opens Na+ and Ca2+ channels, causing depolarization of the receptor membrane that then triggers an action potential
*ordorant results in cAMP increase
what are the 3 types of papillae
- buds foliate (lateral edges), fingiform (front tongue), circumvallate (back tongue)
what is the structure of a taste bud
- taste buds consist of 3 cell types
supporting cells: insulate the recepot
Basal cells dynamic stem cells
gustatory cells taste cells (have taste receptors on surface0
what are the 5 basic taste sensations
Sweet - sugars, saccharin, alcohol, and some amino acids
Bitter - alkaloids such as quinine and micotine
Umami - elicited by the amino acid glutamate
Salt - metal ions (Na+)
Sour = H+ ions
*salt and sour are ion channels rest are G protein
describe the Gustatory pathway
Cranial Nerves VII and IX carry impulses from taste buds to the solitary nucleus of the medulla
- impulses then travel to thalamus and from there fibers branch to
- > gustatory cortex (taste)
- > hypothalamus and limbic system (appreciation of taste
describe the outer ear
- Auricle (pinna) composed of helix (rim) and lobule (earlobe)
*outer ear funnels noise to middle ear
- ear canal is a tube filled with ceruminous glands (antibacterial)
- tympanic membrane (eardrum): connective tissue membrane that vibrates in response to sound -> transfers sound energyto middle ear ossicles
describe the middle
- small air-filled mucosa liend caity
epitympanic recess: superior portion of the middle ear (common site for abcterial infection
pharyngotmpanic tube: connects the middle ear to nasopharyx, equalized pressure in the middle ear cavity with external air pressure
what are the ear ossicles
3 small bones: the malleus, incus, and stapes that transmit vibratory motion of the eardrum to the oval window
- Dampened by the tensor tympani and stapedius muscles
- stabilized by uscles, can reduce signaling goign through ossicles (prevents damage due to loud noise) -> can modify sound to come extent
Describe the Inner ear
Bony labyrinth: Tortuous channels worming their way through the temporal bone that is filled with perilymph
Membranous labyrinth (blue) - Membranous sacs with a potassium- rich endolymph fluid (includes vestibule, cochlea and semicircular canals)
describe the Cochlea
*main centre for sound waves
- spiral, conical, bony cahmber that extends from the anterior vestibule and coils around a bony pillar called the modiolus
- has 3 chambers: scala vestibuli, scala media, scala tympani
what are the main parts of the chochlea, what are they filled with
- has scalas tympani and vestibuli - continuous with helicotreme and filled with perilymph
- scala media (or chochlear duct) is filled with endolymph
- organ of cort is supported by the bony spiral lamina and basilar membrane
provide an overview of the mechanisms of hearing
*sounds = changes in pressure that create sound waves
- Sound vibrations beat against the eardrum
- the eardrum pushes against the ossicles which presses fluid in the inner ear against the oval windows
- this movemnt sets up shearing foces that pull on hair cells
- moving hair cells stimulates the cochlear nerve that sends impulses to the bran
what is sound? what is it composed of?
sound = pressure disturbance (alternating areas of high and low pressure) originating from a vibrating object
- composed of areas of rarefaction and compression sepresented by a sine wave
Frequency vs pitch
Frequency - the number of waves that pass a given point in a given time (Hz; usually cycles/s)
Pitch - perception of different frequencies
sound amplitude vs loudness
Amplitude - intensity of a sound measured in decibels (dB)
Loudness - subjective interpretation of sound intensity
describe transmission of sound to the inner ear
Outer ear - pinna, auditory canal, eardrum
*freq does not change in external ear
- Middle ear - malleus, incus, and stapes to the oval window,
*get amplification, increasing intensity but same frequency
- Inner ear - Stimulation of the organ of Corti and generation of impulses in the cochlear nerve
*dissipation of amplitude
audibel sound waevs for humans
- low sound waves <20 Hz are inaudible
- freq we can hear are 20-20,000 Hc
- audible sound waves: penetrate thru chochlear duct, vibrate the basilar membrane, excite specific hair cells according to freq of the sound
- as sound travels around helicoterma it does not excite the hiar cells bc too low
detection of different frequencies
- basilar membrane has varible sensitivity to sound waves along its length
- higer pitch detected closer to oval window and stapes, lower freq (low pitch) closer to flexible region near helicotrema (distal end)
*means you would hear higher frequency 1st
- detendong where the freq matches up thats wehre the basilar membrane will be displaced, vibration of basilar membrane will then excite hair cells accrding to freq of sound
describe the organ or corti
- composed of supporting cells, outer and inner hair cells
- cochlear nerve attaches to the base of hair cells
- sterocilia (hairs) protrude itno the endolymph and touch the tectorial membrane
describe the excitation of hair cells
Bending cilia opens mechanically gated ion channels and causes a graded potential and the release of a neurotransmitter (probably glutamate)
*activates the choclear nerve
describe the audiotry pathway
- impulses from the cochlea pass via the spiral ganglion to the cochlear nuceli
- from ther , impulses are sent to the superior olivary mucleus, inferior colliculus (auditory relfex centre)
- from there, impulses pass to the auditory cortex
*both cortices receive input from both ears
what perceives pitch? what percieved oudness? localizeation?
Pitch: primary auditory cortex & cochlear nuclei
Loudness: Varying thresholds of cochlear cells & The number of cells stimulated
*localization is perceived by superior olivary nuclei that determines sound
