chemical senses: olfaction and taste

Question 1

smell

Answer 1

-detection of aeresol chemical stimuli
-dysosmia- distorded sense of smell

Question 2

olfactory epithelium

Answer 2

-3 cell types:
-supporting cells- filled with secretory granules and lined with microvilli
-basal cells- undifferentiated stem cells- can turn into more olfactory nerve cells if need be
-olfactory receptor cells- receptor and neuron itself

Question 3

olfactory mechanism

Answer 3

-aerosolized odorant molecules bind receptors-signals travel down and cross cribriform plate (bone that separates nasal cavity and brain)
-synapses with mitral cell at glomerulus in olfactory bulb
-one mitral cell can synapse with multiple olfactory receptor cells to converge to brain

Question 4

olfactory transduction

Answer 4

-odorant molecules -> electrical signal
-activates a G protein -> activate adenylyl cyclase -> ATP to cAMP -> opens cation channels (permeable to Na, K, Ca) -> increase in resting membrane potential -> polarized -> action potential

Question 5

protein stimulus and receptors in olfactory

Answer 5

-many types of receptor proteins
-can bind to receptors but they are selective to specific odorants
-depending on odorant -> receptor will have strong, weak, or no signal
-different receptors can have the different response to same odorant
-if response to given odorant is the same across many receptors -> different patterns emerge for different odorants ->across fiber pattern code

Question 6

olfactory pathway

Answer 6

-granule and periglomerular are inhibitory interneurons that make dendrodendritic synapses on mitral cells to create lateral inhibition in olfactory bulb -> sharpen information into CNS
-pathways include:
-lateral olfactory tract -> to primary olfactory tract
-medial olfactory tract -> to anterior commissure and contralateral olfactory bulb

Question 7

taste

Answer 7

-gustation
-5 tastes: salty, sweet, sour, bitter, umami
-taste receptors are in taste buds
-similar to olfactory (support, receptor, basal cell) -> BUT taste cells are NOT the primary neuron
-epitheliul cells stimulate action potential in primary neuron

Question 8

taste buds

Answer 8

-organized and found in taste papillae
-3 types:
-circumvallate- base, largest,
- foliate- lateral
-fungiform- everywhere, small

Question 9

taste transduction

Answer 9

-depends type of taste
-bitter and sweet- bind to taste receptor cells + G protein -> increase in secondary messenger (IP3 and Ca -> open TRP channels ->
-sour- H+ ions enter directly through -> depolarization
-salt- Na+ ions enter directly through -> depolarization

Question 10

distribution of taste on tongue

Answer 10

-sweet and umami on tip
-salty on the sides in the front
-sour on the sides in the middle
-and bitter in the back

Question 11

encoding taste

Answer 11

-each afferent taste fiber receives input from a population of taste receptors with a distinctive pattern of responses

Question 12

CN innervation of tongue

Answer 12

-posterior 1/3 (bitter and sour)- glossopharyngeal (9)
-anterior 2/3 (sweet umami salt)- facial (7)
-throat- vagus (10)
-all ascend as one in the solitary tract -> solitary nucleus of medulla -> ipsilaterally to third order -> leave thalamus -> terminate in taste cortex