L33 Chemical Senses

Question 1

what are the basic taste qualities?

Answer 1

salty - sodium chloride
sour - acids and H ions
sweet - sugars (sucrose)
bitter - toxic or poisonous components

umami - MSG?

Question 2

describe the taste bud receptor cells - what occurs at apical and basal poles?

Answer 2

apical pole - site of signal transduction

basal pole - site of transmitter release onto afferent fibers

Question 3

where are basal cells located and what are they able to do?

Answer 3

located at the basal pole

differentiate into new taste receptors cells

Question 4

what signal transduction pathway does Salt and sour used?

Answer 4

ionotropic

Question 5

what signal transduction pathway does sweet use

Answer 5

metabotropic - cAMP pathway

Question 6

what signal transduction pathway does bitter use

Answer 6

metabotropic - IP3/DAG pathway

Question 7

does the gustatory pathway cross at the midline?

Answer 7

no - completely ipsilateral tract!

Question 8

what is the anterior 2/3rd of the tongue innervated by?

Answer 8

facial n. (CN VII)

Question 9

what is the posterior 1/3rd of the tongue innervated by?

Answer 9

glossopharyngeal n. (CN IX)

Question 10

what is the very back of the tongue and glottis innervated by?

Answer 10

vagus n. (CN X)

Question 11

what is the major different between smell and taste?

Answer 11

smell tens of thousands of different smells

only have 4 or 5 different taste qualities

Question 12

where are olfactory receptor neurons ?

Answer 12

imbedded in olfactory epithelium with their cilia hanging in the nasal cavity

Question 13

how often do basal cells differentiate and replace olfactory receptor neurons?

Answer 13

every 60 days

Question 14

what do all the multiple small afferents form the receptor cells form?

Answer 14

CN-1 - olfactory n.

Question 15

what does CN I provide input to?

Answer 15

olfactory bulb

Question 16

the afferents are covered in a ____ that are neither oligodendrocytes or schwann cells

Answer 16

sheath

Question 17

the afferents pass though the _____ and synapse on the _____ that is associated with the particular receptor neuron type

Answer 17

cribiform plate

glomerulus

Question 18

what signal transduction mechanism is used in the olfactory system?

Answer 18

metabotropic cAMP pathway

Question 19

each receptor neuron expresses one of the 1000 different receptor proteins sensitive to a ______

Answer 19

single odorant

we use a combinations to interpret and understand such an array of smells

Question 20

where does vertical information pass?

Answer 20

from olfactory receptor neuron -> cribiform plate -> bulb

Question 21

where does horizontal information pass

Answer 21

inhibitory interneurons assists in segregating the vast number of odorants into individual smells based on the combination of levels of excitement of each receptor type

Question 22

what does the olfactory cortex include

Answer 22

peri-amygdaloid cortex
piriform cortex
entorhinal cortex

Question 23

unlike the other pathways, the olfactory pathway ____ reaches the cortex without a ______ projection

Answer 23

directly

thalamo-cortical

Question 24

the olfactory cortex has close relation to the ____ which controls emotions. Hence, why it is difficult to remain emotionally indifferent when we smell good or bad smells

Answer 24

limbic system

Question 25

describe the vomernasal organ

Answer 25

discovered in 1800’s
found to work with pheromone communication in mammals
1998 - study on female menstrual cycles showed that there is significant evidence for the validity of human pheromones - ovulation pheromones slow LH

Question 26

define hypogeusea

Answer 26

decreased taste function usually due to oral cavity pathology (secondary to salivary gland dysfunction) leading to taste bud destruction

Question 27

define ageusea

Answer 27

total loss of taste function
may be due to lesion on chorda tympani (CN 7 facial)
usually in conjugate with BELLS PALSY (CN 7) causing same side taste loss to anterior 2/3 of tongue
can also be use to WALLENBERGS SYNDROME (lateral medullary syndrome) to to an infarction of the lateral medulla caused by an occlusion to the PICA

Question 28

define hyposmia

Answer 28

decreased smell function (more common than hypogeuse) where the pt complains that they cannot taste anything but it is usually inadequate taste because the loss of the smell of the food

Question 29

define anosmia

Answer 29

total loss of smell most likely due to compression of the olfactory tract by tumors, particularly meningiomas

Question 30

define olfactory hallucinations

Answer 30

partical epilectic seizures originating in the vicinity of the uncut
will commonly induce olfactory hallucinations of pungent and unpleasant smells but they do not actually exist.