Module B: Chemical Senses - Olfactory

Question 1

Olfactory organ is in the upper/lower part of nose

Answer 1

upper

Question 2

the olfactory organ can detect _______ different substances

Answer 2

200, 000

Question 3

Olfactory system is involved in communication: Pheromones

Answer 3

-signalling reproductive behaviour, marking teritory, signalling aggression, fear

Question 4

Olfactory epithelium in humans (small) =

Olfactory epithelium in dogs =

Answer 4

Humans = 10cm2
Dogs = 170cm2

Question 5

Human has __ olfactory receptors
Rat has ___ olfactory receptors
Dog has ___ olfactory receptors
Blodhound dog has ___ olfactory receptors

Answer 5

12 million
15 million
1 billion
4 billion

Question 6

Sense of smell declines with age & also effects sense of taste. Women or Men have a better sense of smell at all ages?

Answer 6

Women

Question 7

Accessory olfactory system can detect ___. Involves ____ organ, in the base of the nose

Answer 7

Pheromones; Vomeronasal organ

Question 8

In carnivores, including dogs and cats is the Vomeronasal system, what is this:

Answer 8

Vomeronasal system comprises of the vomeronasal organ and the accessory olfactory organ, where axons from chemosensory receptor cells in the vomeronasal organ synapse
-Projections from the accessory olfactory bulb go to the Amygadla and hypothalamus

Question 9

The 2 different classes of vomeronasal receptor proteins:

Answer 9

V1R and V2R

Question 10

Mucus in the olfactory glans contains:

Answer 10

Mucopolysaccharides, antibodies, odorant binding proteins

Question 11

How many olfactory cells are there?

Answer 11

10^6

Question 12

Olfactory receptors turnover rate =

Answer 12

Basal stem cell divides to form new receptors 4-8 weeks

Question 13

Olfactory transduction (see slide 30 in lec2) See pg 266 in Bear

Answer 13

• Odorants
• Binding to membrane odorant receptor proteins
• G-protein (Golf) stimulation
• activation of adenyl cyclase
• formation of cAMP (2nd messenger)
• cAMP binds to cation channel
• cation channel opens and influx of Ca2+ and Na+
• this influx opens Cl- channels (Cl- outflux)
• current flow and membran depolarization

(Ca2+ is gotten rid of through the Na/Ca exchanger)

Question 14

Odorant receptors are coded for by odorant receptor genes (ORgenes)
____ genes in humans
____ genes in mouse

Answer 14

900; 1500

Involves 1 gene, 1 receptor hypothesis

Question 15

Olfactory epithelium is organized into ____, each conntains receptor cells that express a different/or same subset of receptor genes. Within each zone individual receptor types are scattered randomly

Answer 15

zones; a different subset of receptor genes

Question 16

What 2 senses work together to provide perception of flavour

Answer 16

olfaction and gustation

Question 17

Glomeruli are spherical accumulations of neuropil, that lie beneath the surface of the olfactory bulb. What synapses here

Answer 17

primary olfactory axons, which synapse with Mitral cell dendrites

Question 18

Within each glomerulus the axons of the receptor neurons contact apical dendrites of….

Answer 18

Mitral cells

Question 19

Mitral cells are

Answer 19

Principal projection neurons of the olfactory bulb

Question 20

The Mitral cell dendrite gives rise to elaborate….

Answer 20

tuft of branches

Question 21

Layer order:

Answer 21

Glomerulus –> external plexforn layer –> Mitral cell layer –> internal plexiform layer –> granule cell layer