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Flashcards in Olfaction and Gustation Deck (42)
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3 types of cells in the olfactory epithelium.

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


1st order cells of Olfactory system.

olfactory receptor cells


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

olfactory bulb


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.

tract & stria


Jacobson’s Organ/Vomeronasal Organ.

- 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


The olfactory cortex processing of information bypasses the?



Olfactory epithelium anatomy.

- 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


How do the cilia function?

- 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


Explain the neuron synapses that occur during smell.

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


Medial stria

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


Primary odors.

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


Mechanism of excitation for smell.

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


Olfactory receptor cell.

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


How are smells differentiated?

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


T/F First order taste cells are neurons.



Anatomical papillae of taste buds.

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


T/F Taste receptors are regenerate.



T/F Second order cells for taste are neurons.



Morphology of taste receptors.

- 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


Sweet taste.

- 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


Salty taste.

- made of ionized salts
- dependent on conc. of cations in salt


Sour taste.

due to proton concentration (Hydrogen ions)


Bitter taste.

- 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.


Umami taste.

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


Metallic taste.

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


Thresholds for taste.

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)


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



Taste coding.

- Along Labeled Lines
- Patterns of Neural Activity


Taste Receptors are carried by CN?

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


Ipsilateral pathway for taste.

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