Olfaction and Taste

Question 1

Gustation

Answer 1

Taste: water and fat soluble substances

Question 2

Three types of chemical senses in the human

Answer 2

1. olfaction 2, taste 2. trigeminal “irritant” detection

Question 3

Olfactory Epithelium

Answer 3

10 cm2 of the upper lining of the nasal cavity with olfactory receptor neuron (ORN) - bipolar neuron, dendrites extend into nasal cavity – turn into a knob with small microvilli

Question 4

ORNs

Answer 4

are associated with specialized supporting cells, sensory nerve endings, and the ducts of mucus secreting cells. have a limited life span and are constantly regenerating. ORN microvilli are specific odorant receptor proteins (specific odorant molecules bind to these)

Question 5

binding of an odorant molecule to an odorant receptor protein

Answer 5

activates the ORN-specific cytoplasmic G -protein –> adenyl cyclase —> cAMP —> action potential

Question 6

each ORN expresses

Answer 6

only one specific odorant receptor protein (can interact with more than one molecule)

Question 7

ORN axons in the cribiform plate

Answer 7

are known as “filia” and form the “true olfactory nerve” –> synapse with mitral cells —> olfactory bulb glomeruli (hypocellular, synapse rich)

Question 8

mitral cells are

Answer 8

FORM THE OLFACTORY TRACT! The major projection neuron found in the olfactory bulb and interact with local neurons (tuft, periglomerular, granule cells). recieve input from 1000 ORNs (that express the same odorant receptor protein)

Question 9

convergence

Answer 9

HUGE convergence to the glomerulus, thought to increase the sensitivity to the system to any given odorant

Question 10

anterior olfactory nucleus

Answer 10

receives projections from the ORNs and send axons back to the olfactory bulbs (bilateral processing)

Question 11

lateral olfactory tract

Answer 11

where most axons in the olfactory tract go - the major output pathway for the olfactory bulb. synapses with the piriform cortex (parahippocampal gyrus) - also minor synapse with teh entorhinal cortex and the amygdala

Question 12

how is the olfactory system different than other sensory systems?

Answer 12

it reaches the cortex before the thalamus

Question 13

Piriform cortex projects to…

Answer 13

the entorhina cortex, the amygdala, the hippocampus, thalamus (cognitive and emotional activities), hypothalamus (food intake), orbital frontal cortex (cognitive/emotional response)

Question 14

Taste buds

Answer 14

contain taste cells , mixed with the non-keratinizing squamous epithelium that covers the papillary projections of the dorsal tongue. contain an opening or pore. have taste receptor proteins

Question 15

taste receptor proteins

Answer 15

5: salty (front), sour (lateral), bitter (back), sweet (front), umami (savory, front) SUBSS

Question 16

two types of taste receptor proteins

Answer 16

1. simple ion channels (salty/sour) 2. g-protein coupled (bitter, sweet, umami)

Question 17

taste cells

Answer 17

express a single type of taste receptor protein and release a neurotransmitter when activated by a tastant attaching to a tastant receptor protein

Question 18

basal portion of taste cells….

Answer 18

synapse with a gustatory nerve ending –> peripheral sensory ganglia –> CN VII, IX, X -> solitary nucleus, medulla oblongata

Question 19

solitary nucleus projections based on taste go…

Answer 19

1. VPM —> insular cortex (frontal operculum) 2. cortical areas 3. amygdala/ hypothalamus (relay nuclei, SURVIVAL FUNCTIONS)

Question 20

irritant detection

Answer 20

via CN V, “pain receiving pathways”, (receptors in the mouth, nasal cavity, and teh conjuctivae). CN V —> brainstem —> spinal trigeminal nucleus —> solitary nucleus pathways/reticular formation –> lacrimation/secretion of mucus in the nasal cavity (dilute the offending chemical agent)