5. Olfaction

Question 1

the detection of chemicals in the air

Answer 1

olfaction

Question 2

detects odorants that bind to olfactory receptors

Answer 2

olfactory system

Question 3

detects tastants that bind to gustatory receptors

Answer 3

gustatory system

Question 4

both the olfactory system and the gustatory system contribute to our perception of:

Answer 4

taste

Question 5

do fish have an olfactory system?

Answer 5

yes

Question 6

all vertebrates have a _____, and most land vertebrates have an _____

Answer 6

main olfactory system, accessory olfactory system (vomeronasal system)

Question 7

the main olfactory epithelium (MOE) projects to the:

Answer 7

main olfactory bulb (MOB)

Question 8

the vomeronasal organ (VNO) projects to the:

Answer 8

accessory olfactory bulb (AOB)

Question 9

a sieve-like structure between the anterior cranial fossa and the nasal cavity (forms part of the ethmoid bone)

Answer 9

cribiform plate

Question 10

where are the olfactory receptors located?

Answer 10

sensory cilia

Question 11

how many sensory cilia does each dendritic knob have?

Answer 11

20-30

Question 12

olfactory receptor cells project to:

Answer 12

mitral cells

Question 13

site where dendrites of mitral cells interact with the axons of olfactory receptor cells

Answer 13

glomerulus

Question 14

mitral cell axons project to the:

Answer 14

brain

Question 15

what is the lifetime of olfactory receptor cells?

Answer 15

~60 days

Question 16

olfactory receptor cells arise from:

Answer 16

basal (stem) cells

Question 17

odorant molecules dissolve in the mucous in the nasal cavity, interact with odorant binding proteins in the mucous, and then:

Answer 17

bind with olfactory receptors on the cilia

Question 18

the binding of odorants to olfactory receptors leads to:

Answer 18

depolarization (and hopefully an action potential)

Question 19

all olfactory proteins are composed of:

Answer 19

seven transmembrane segments (GPCRs)

Question 20

what type of pathway do olfactory receptors activate?

Answer 20

GPCR pathway with cAMP as a second messenger

Question 21

which segments of the olfactory receptor show considerable sequence variability?

Answer 21

segments 3, 4, and 5

Question 22

which segments of the olfactory receptor do odorants bind to?

Answer 22

segments 3, 4, and 5

Question 23

each olfactory receptor neuron expresses:

Answer 23

only one type of olfactory receptor protein

Question 24

the number of olfactory receptor genes can reflect:

Answer 24

the range of scents detected

Question 25

when the odorant is in a K+/Cl- solution the initial inward current is due to:

Answer 25

increased extracellular K+

Question 26

does the odorant itself open the receptor channels?

Answer 26

no (it is a G-protein coupled mechanism)

Question 27

list the five major steps of odorant opening ion channels via a GPCR mechanism?

Answer 27

1) odorant binds to the olfactory receptor protein (GDP exchanged for GTP causing the alpha-subunit to separate from the G-protein) 2) GTP alpa subunit activates adenylate cyclase and ATP is converted to cAMP 3) cAMP opens the cyclic-nucleotide gated cation channel 4) depolarization results from Na+ and Ca++ influx 5) Ca++ influx cause Cl- channels to open, Cl- flows out of the cell maintaining the depolarization

Question 28

are transgenic mice lacking cAMP gated channels able to discriminate odours

Answer 28

no

Question 29

some olfactory receptor proteins many be coupled to G-proteins that activate _____ instead of _____

Answer 29

phospholipase C (PLC), adenylate cyclase (AC)

Question 30

by activating PLC pathways, IP3 can:

Answer 30

act on Ca++ channels directly

Question 31

G-protein coupled olfactory receptors that utilize PLC are important in:

Answer 31

invertebrate olfaction (less so in vertebrates)

Question 32

different families of olfactory receptor proteins are localized to:

Answer 32

4 or 5 zones in the olfactory epithelium and olfactory bulb

Question 33

each olfactory zone contains ____ olfactory receptor proteins that are closely related

Answer 33

100-200

Question 34

each glomerulus receives input from olfactory receptors containing:

Answer 34

a single olfactory receptor protein

Question 35

true or false: there is a segregation of information from each olfactory receptor protein

Answer 35

true

Question 36

it is suggested that the olfactory bulb is organized into a:

Answer 36

chemotopic map

Question 37

true or false: olfactory receptor proteins respond to unique odours

Answer 37

false (each odorant protein can recognize more than one odorant)

Question 38

how is smell determined?

Answer 38

by a pattern of activity across all olfactory receptors (population coding)

Question 39

true or false: one odorant can excite more than one neuron

Answer 39

true

Question 40

most land vertebrates have a vomeronasal organ specialized for:

Answer 40

detecting pheromones

Question 41

chemicals released by an organism that cause a physiological and/or behavioural response in other individuals of the same species

Answer 41

pheromones

Question 42

what is an example of a pheromone/vomeronasal system?

Answer 42

LH and testosterone are released when male mice/hamsters are exposed to chemosensory stimuli from females

Question 43

in mammals, the nasopalatine duct is normally closed, but opens when:

Answer 43

an odour associated with a pheromone is detected

Question 44

in snakes and lizards, the ____ draws pheromones into the vomeronasal organ

Answer 44

tongue

Question 45

the curling and opening of the mouth that allows scents to enter the vomeronasal organ (VNO)

Answer 45

Flehman response

Question 46

vomeronasal receptor neurons have _____ rather than _____

Answer 46

microvilli, cilia

Question 47

is the vomeronasal epithelium organized similarly to the olfactory epithelium?

Answer 47

yes

Question 48

what type of receptors are vomeronasal receptor proteins?

Answer 48

G-protein coupled receptors

Question 49

there are as many as 300 different vomeronasal receptor proteins in mice which are each responsive to:

Answer 49

a single (or a few) specific chemical compounds (important for mating responses)

Question 50

what are the two major families of vomeronasal receptor proteins?

Answer 50

- V1R (coupled to Gi) - V2R (coupled to G0)

Question 51

both V1R and V2R use IP3 and DAG as second messengers to open:

Answer 51

TRPC2 cation channels

Question 52

the organization of the vomeronasal receptor cells projections to the accessory olfactory bulb is similar to:

Answer 52

the organization of olfactory epithelium projections to the olfactory bulb

Question 53

olfactory bulbs project to the:

Answer 53

brain

Question 54

where in the brain does the olfactory bulb project to?

Answer 54

the piriform cortex (PC) --> aka the olfactory cortex

Question 55

where is the olfactory cortex located in humans?

Answer 55

deep in the medial part of the medial temporal lobe (bypasses the thalamus)

Question 56

responsible for the identification of odours in the olfactory cortex

Answer 56

the piriform cortex (PC)

Question 57

the lateral amygdala gets information from the:

Answer 57

main olfactory bulb

Question 58

intimately linked with the hypothalamus (sexual behaviours, aggression, other social behaviours)

Answer 58

the medial amygdala

Question 59

pheromones lead to:

Answer 59

hormones

Question 60

the main olfactory bulb is associated with the _____, and the accessory olfactory bulb is associated with the ______

Answer 60

lateral amygdala, medial amygdala

Question 61

the bed nucleus of the stria terminalis (BST), extensive connections with the:

Answer 61

amygdala and hypothalamus