L33 Chemical Senses Flashcards
what are the basic taste qualities?
salty - sodium chloride
sour - acids and H ions
sweet - sugars (sucrose)
bitter - toxic or poisonous components
umami - MSG?
describe the taste bud receptor cells - what occurs at apical and basal poles?
apical pole - site of signal transduction
basal pole - site of transmitter release onto afferent fibers
where are basal cells located and what are they able to do?
located at the basal pole
differentiate into new taste receptors cells
what signal transduction pathway does Salt and sour used?
ionotropic
what signal transduction pathway does sweet use
metabotropic - cAMP pathway
what signal transduction pathway does bitter use
metabotropic - IP3/DAG pathway
does the gustatory pathway cross at the midline?
no - completely ipsilateral tract!
what is the anterior 2/3rd of the tongue innervated by?
facial n. (CN VII)
what is the posterior 1/3rd of the tongue innervated by?
glossopharyngeal n. (CN IX)
what is the very back of the tongue and glottis innervated by?
vagus n. (CN X)
what is the major different between smell and taste?
smell tens of thousands of different smells
only have 4 or 5 different taste qualities
where are olfactory receptor neurons ?
imbedded in olfactory epithelium with their cilia hanging in the nasal cavity
how often do basal cells differentiate and replace olfactory receptor neurons?
every 60 days
what do all the multiple small afferents form the receptor cells form?
CN-1 - olfactory n.
what does CN I provide input to?
olfactory bulb
the afferents are covered in a ____ that are neither oligodendrocytes or schwann cells
sheath
the afferents pass though the _____ and synapse on the _____ that is associated with the particular receptor neuron type
cribiform plate
glomerulus
what signal transduction mechanism is used in the olfactory system?
metabotropic cAMP pathway
each receptor neuron expresses one of the 1000 different receptor proteins sensitive to a ______
single odorant
we use a combinations to interpret and understand such an array of smells
where does vertical information pass?
from olfactory receptor neuron -> cribiform plate -> bulb
where does horizontal information pass
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
what does the olfactory cortex include
peri-amygdaloid cortex
piriform cortex
entorhinal cortex
unlike the other pathways, the olfactory pathway ____ reaches the cortex without a ______ projection
directly
thalamo-cortical
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
limbic system
describe the vomernasal organ
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
define hypogeusea
decreased taste function usually due to oral cavity pathology (secondary to salivary gland dysfunction) leading to taste bud destruction
define ageusea
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
define hyposmia
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
define anosmia
total loss of smell most likely due to compression of the olfactory tract by tumors, particularly meningiomas
define olfactory hallucinations
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.
