Taste (Gustation) and Smell (Olfaction)

Question 1

Pheromones

Answer 1

chemical signal released by a member of a species that can be sensed by another member or a member of a different species triggering an innate response; implicated in mating, fighting, and communication

Question 2

Accessory Olfactory Epithelium and Accessory Olfactory Bulb

Answer 2

• epithelium - specialized part of the olfactory epithelium in animals which sends signals to the accessory olfactory bulb
• bulb - sends signals to the brain

Question 3

Vomeronasal System

Answer 3

structure within the olfactory epithelium composed of basal and apical cells with receptors
-humans have a vomeronasal organ but no accessory olfactory bulb, and thus we rely very little on pheromones

Question 4

Pathway of Vomeronasal System

Answer 4

• pheromone comes in and activates a GPCR receptor on basal and apical cells
• these cells then send the signal up the axon through the olfactory bulb to the glomerulus –> mitral/tufted cell –> amygdala (located in the temporal lobe and associated with emotional reactions and memory/decision making)

Question 5

Olfactory Epithelium

Answer 5

-contains epithelia and olfactory sensory cells

Question 6

Cribriform Plate

Answer 6

bones with little holes allowing the olfactory sensory cells to send their projections to the brain

Question 7

Olfactory Bulb

Answer 7

bundle of nerves that send projections through the cribriform plate to the olfactory epithelium which branch off

• at the end of each connection are receptors that are specific to one molecule
• molecule travels through nose and binds its specific receptor

Question 8

Olfaction Pathway

Answer 8

• Olfactory sensory cells, dispersed between olfactory epithelial cells, have different receptors. Let’s say one such cell has receptor for benzene
• Benzene binds to a GPCR receptor which initiates the dissociation of the G-protein from the receptor
• G-protein goes to bind to the ion channel, opening it up, allowing for the influx of ions triggering an action potential
• goes to the cribriform plate –> glomerulus –> activates mitral/tufted cell –> amygdala and piriform cortex –> orbitofrontal cortex

Question 9

Glomerulus and Mitral/Tufted Cells

Answer 9

• glomerulus = designation point within the olfactory bulb for various sensory olfactory cells that are sensitive to the same molecule
• mitral/tufted cells = synapses to both the glomerulus and the brain (middle man)

Question 10

Labeled-Line Theory of Olfaction

Answer 10

describes a scenario where each receptor would respond to specific stimuli and is directly linked to the brain

Question 11

Vibrational Theory of Olfaction

Answer 11

asserts that the vibrational frequency of a molecule gives that molecule its specific odor profile

Question 12

Steric Theory/Shape Theory

Answer 12

asserts that odor molecules fit into receptors similar to a lock and key

Question 13

Anosmia

Answer 13

inability to perceive odor

Question 14

Five Tastes

Answer 14

sweet, bitter, umami (ability to taste glutamate)
-work via GPCR receptors
sour, salty
-work via ion channels

Question 15

Taste Buds

Answer 15

contain taste receptor cells and are contained within papillae
-each taste bud has all 5-receptor cells that can detect each taste; each taste can be detected anywhere on the tongue

Question 16

Papillae

Answer 16

contain the taste buds

• Fungiform = anterior papillae; largest concentration of taste buds; mushroom-like structures
• Foliate = papillae on the sides of the tongue; folded structures
• Circumvallate = papillae at the back of the tongue; plateau shaped structures
• Filiform = papillae at the center of the tongue that contain no taste buds

Question 17

Labelled Lines Model

Answer 17

each taste bud has 5 axons (for the 5 tastes), all which send information to different locations of the gustatory cortex