Lecture #17

Question 1

what are the there systems that allow for the interaction and recognition of airborne signals?

Answer 1

olfactory, vomero-nasal, and gustatory

Question 2

what does the olfactory system apply to?

Answer 2

deals with odorants

Question 3

what does the vomero-nasal organ apply to?

Answer 3

designed to detect pheromones shared by many species (not humans)

Question 4

what is the goal of the olfactory system?

Answer 4

to manage airborne molecules (odorants) that are fundamental to give information about other animal / plants and to detect noxious substances

Question 5

what is the goal of the voter-nasal system?

Answer 5

to recognize predators

Question 6

what the main nerves of the olfactory system?

Answer 6

olfactory receptor neurons (ORNs)

Question 7

describe the localization of ORNs:

Answer 7

the cell body is located in the periphery (especially in the nose mucosa) while the axons forth nerve 1 (olfactory nerve) and move from the periphery to the CNS through the cribriform plate

Question 8

what protects the ORNs?

Answer 8

a huge amount of mucus produced by the mucosal cells - others the nerves would be directly exposed to the neural cavity

Question 9

where is the first synapse of the olfactory bulb?

Answer 9

in the glomerular region

Question 10

where does the information travel first from the olfactory division?

Answer 10

directly contacts regions of the cerebral cortex, such as the piriform cortex, olfactory cortex, and the amygdala

Question 11

does the olfactory stimulation reach the thalamus?

Answer 11

the input signal goes directly to the brain and then it can be transmitted to the thalamus

Question 12

what is a unique characteristic of this sensory system?

Answer 12

the absence of a topographic map

Question 13

what is a lack of olfactory sensation called?

Answer 13

anosmia

Question 14

what can cause anosmia?

Answer 14

elicited by specific mutations involved in signal transduction and in the generation of trains of action potential

Question 15

what diseases can trigger an alteration of our sense of smell?

Answer 15

• Alzheimers
• early sign of Parkinsons
• schizophrenia or bipolar disorders can experience olfactory hallucinations

Question 16

what are the accessory and supporting cells in the mucosa?

Answer 16

form the Bowman glads releasing mucus and supporting cells are also present both on the slide of the ORNs and on the basolateral part of the epithelium

Question 17

what is unique about the sensory system in the CNS?

Answer 17

these neurons can regenerate

Question 18

what is different between mice and humans in regards to the olfactory system?

Answer 18

some cells are locally generated, so when dealing with olfactory receptors that are between the cribriform plate and the olfactory mucosal region, were are not dealing with neural stem cells derived from the SVZ - they are regenerated ORNs → can grow and send their axons to the cribriform plate and are unmyelinated

in humans regeneration is debated

Question 19

describe ORNs:

Answer 19

transmembrane proteins that are classical G-coupled protein receptors containing several variable domains in both the N-terminal region, extracellular loop, and intermembrane domains

Question 20

in mammals, what is unique about the ordorant receptor gene family?

Answer 20

it is the largest known single gene family representing 3-5% of the genome

Question 21

describe the molecular mechanism of odorant transduction:

Answer 21

molecular cascade starts with the interaction of the odorant with the G-coupled protein receptor G(olf)

activation leads to the activation of adenylyl cyclase III localized on the inner side of the pm (responsible for the conversion of ATP to cAMP)

conversion activates the cAMP-gated ion channels allowing the entry of sodium and calcium inside the cell leading to the depolarization of the membrane

Question 22

what is the olfactory receptor in the CNS?

Answer 22

glomeruli - regions receive axons of individual ORNs

Question 23

describer the mitral cells of the olfactory bulb:

Answer 23

extend a short cytoplasmic dendrite tot the glomerulus and a long axon to contact the piriform cortex, amygdala, or other cortical nuclei

in this case the crossing of the midline does not occur, these cells start from the olfactory bulb and sent axons to the ipsilateral side

Question 24

what cells flank the mitral cells?

Answer 24

tufted cells

Question 25

what are the function of tufted cells?

Answer 25

involved olfactory perception (although the mitral cells are still the main cells involved)

Question 26

how do the granule cells interact with the mitral cells?

Answer 26

they are di-dentritic cells that only express dendrites and they flank the mitral cells

inhibitory → constitute the innermost layer of the vertebrate olfactory bulb and synapse primarily on the basal dendrites of the mitral cells in the external plexiform layer

Question 27

what cells flank the glomerulus?

Answer 27

periglomerular cells

Question 28

describe the activation of the glomeruli in response to complex odors?

Answer 28

there is thee activation of few glomeruli but the reason is unknown

Question 29

where is the vomeronasal organ located?

Answer 29

laterally under the gumline

Question 30

what is another name for the vomeronasal organ (VNO)?

Answer 30

Jacobson’s organ

Question 31

what do mammals use the VNO for?

Answer 31

can sense the odorants of predators and extert homeostatic or aggressive responses when that odor is perceived

Question 32

what is detected by the VNO?

Answer 32

pheromones → called kairomones in animals

Question 33

do humans have the VNO?

Answer 33

no → we can somehow still detect pheromones but is is unsure how

Question 34

describe the vomeronasal receptors:

Answer 34

g-couples protein transmembrane receptors called V1R and V2R

TRP is one of the ion channel involved in the perception of pheromones (also involved in the detection of temperature)