Olfaction and Gustation

Question 1

3 types of cells in the olfactory epithelium.

Answer 1

Supporting cells - mature to become basal cells
Basal cells - mature to become olfactory receptor cells
Olfactory receptor cells - neuronal in nature but have capability of regeneration, have a typical life span and at end of it will die, replaced by basal cells, constant turnover of olfactory receptor cells

Question 2

1st order cells of Olfactory system.

Answer 2

olfactory receptor cells

Question 3

1st order axons are projected through cribriform plate to this.

Answer 3

olfactory bulb

Question 4

From the bulb the _____ and ____ are developed, creating the 3 pathways that 2nd and 3rd order fibers will take to get to the olfactory cortex.

Answer 4

tract & stria

Question 5

Jacobson’s Organ/Vomeronasal Organ.

Answer 5

• area of olfactory epithelium that is very vestigial in nature, embedded in vomer bone of nose
• pheromone detection/recognition
• synchronize female menstrual cycles
• affect female choice of mates
• cause mother/infant bonding
• alter concentration, productivity
• change perception of people/environments
• classical conditioning

Question 6

The olfactory cortex processing of information bypasses the?

Answer 6

thalamus

Question 7

Olfactory epithelium anatomy.

Answer 7

• receptor cells located in patch of tissue 3 cm square in size
• embedded in epithelium and apex of cells will have series of cilia that are exposed to external world
• axons will bundle to create fascicles to pass through cribriform plate to the olfactory bulb to synapse on 2nd and 3rd order cells IN bulb

Question 8

How do the cilia function?

Answer 8

• cilia are normally in mucous, which traps the odorant and allows it to diffuse through to bind with receptors on the cilia themselves
• receptors for odorants cause chemical changes, initiating action potential that if made to axon will propagate to the bulb

Question 9

Explain the neuron synapses that occur during smell.

Answer 9

receptor cells–>cribiform plate–>glomeruli–>mitral and tufted cells–>granular and periglomerular spread laterally–>anterior olfactory nucleus–>final output–>stria–>amygdaloid nucelus (olfactory cortex)

Question 10

Medial stria

Answer 10

from one olfactory bulb and tract to the contralateral olfactory bulb and tract

Question 11

Primary odors.

Answer 11

Musky - perfumes/aftershave
Putrid- rotten eggs (sulfur)
Pungent- vinegar
Camphoraceous- mothballs, vicks vapor rub
Ethereal- dry cleaning fluid, ozone, cleaning solutions
Floral- roses
Pepperminty- mint gum

Question 12

Mechanism of excitation for smell.

Answer 12

G-coupled protein/metallic Ion binding sites- 350 human receptor genes, ~ 1300 mouse genes, ~10,000 odors detected, odors highly subjective based on gender, age, state of health, personal history

Question 13

Olfactory receptor cell.

Answer 13

Pear shaped cell, On outside of epithelial lining is a bulbous knob with series of cilia, they are neurons and mitotic

Question 14

How are smells differentiated?

Answer 14

labeled lines coding, all take the same path but every type of smell/odor is going to have a specific code, also graded receptor potentials (concentration)
Ex: peppermint may be burst of 4 action potentials, whereas putrid will be a burst of 10 action potential in a row

Question 15

T/F First order taste cells are neurons.

Answer 15

False

Question 16

Anatomical papillae of taste buds.

Answer 16

Fungiform papillae - taste buds located along the border
Foliate papillae - taste buds along the side
Circumvallate Papillae - taste buds are inside groove surrounding the papillae

Question 17

T/F Taste receptors are regenerate.

Answer 17

True

Question 18

T/F Second order cells for taste are neurons.

Answer 18

True

Question 19

Morphology of taste receptors.

Answer 19

• same for taste buds, regardless of the type of papillae they are located in
  supporting cells–>basal cells–>receptor cells
• Receptor cells will have afferent innervation, that will be the first neuron in the system, but the second order cell in the system

Question 20

Sweet taste.

Answer 20

• caused by organic molecules that cause a stereochemical interaction with receptor cell, initiating AP and stereochemical interactions
  organic molecules with more hydroxyl groups will be sweeter than those organic molecules with less hydroxyl groups

Question 21

Salty taste.

Answer 21

• made of ionized salts

- dependent on conc. of cations in salt

Question 22

Sour taste.

Answer 22

due to proton concentration (Hydrogen ions)

Question 23

Bitter taste.

Answer 23

• long chain organic molecules + nitrogen
• By attaching a nitrogen atom it creates a more basic compound (Alkaloids)
• Major poisons are alkaloids, are easily detectable in very low conc.

Question 24

Umami taste.

Answer 24

• L-glutamate
• Certain ribonucleotides i.e. guanosine monophosphate (GMP) and inosine monophosphate (IMP)
• “pleasant savory taste”

Question 25

Metallic taste.

Answer 25

Dysgeusia- zinc deficiency, certain drugs | Pathological condition - detecting metallic on a regular basis

Question 26

Thresholds for taste.

Answer 26

``` Sweet: 0.01 moles of glucose Salt: 0.01 moles of NaCl Sour: 0.001 moles of HCl Bitter: 0.00001 moles of quinine (threshold is less for substances that could harm the body i.e. poisons) ```

Question 27

T/F All receptors anywhere on the tongue can detect all flavors.

Answer 27

True

Question 28

Taste coding.

Answer 28

- Along Labeled Lines | - Patterns of Neural Activity

Question 29

Taste Receptors are carried by CN?

Answer 29

VII, IX, and X (each nerves will ascend ipsilaterally to solitary nucleus in medulla)

Question 30

Ipsilateral pathway for taste.

Answer 30

Afferent Fibers-->Solitary Nucleus-->VPM of the thalamus (head region)/Parabrachial nucleus/hypothalamus-->Postcentral gyrus- insular cortex/amygdala

Question 31

From solitary nucleus there is a major pathway to ____________ nucleus and _____ (both in thalamus).

Answer 31

parabrachial; VPM (minor pathways to the amygdala and hypothalamus)

Question 32

Emotional responses to tastes is controlled by the pathway to?

Answer 32

amygdala

Question 33

From VPM taste info goes to?

Answer 33

primary sensory cortex

Question 34

From parabrachial nucleus, taste info goes to?

Answer 34

insula

Question 35

Intermediate Stria

Answer 35

goes through septum basal forebrain (anterior perforated substance) region to thalamus, but not to the cortex

Question 36

Lateral Stria

Answer 36

- breaks into 3 - one to the pyriform cortex, accessory to olfactory cortex (entorhinal) - one to the entorhinal cortex - one to the amygdala and hippocampus, connection to limbic system for learning and memory

Question 37

Orbitofrontal cortex

Answer 37

pyriform and entorhinal cortex (lateral stria)

Question 38

Smell information crosses the midline via which structure?

Answer 38

anterior commissure (via the medial stria)

Question 39

Morphology of olfactory/taste receptors.

Answer 39

supporting cell-->basal cell-->receptor cell

Question 40

Fungiform papilla

Answer 40

- look like mushrooms | - taste buds are located along the borders of the papillae

Question 41

Filiform papilla

Answer 41

- look like a little flame | - taste buds are embedded along the sides of the papillae

Question 42

Circumvallate papilla

Answer 42

- there is a large groove surrounding the papillae and the taste buds are located inside the walls inside the groove - these papillae are found at the root of the tongue