NEU Quiz Tast/Smell Flashcards
What cell types make up the olfactory epithelium, and what are their functions?
basal, supporting, and olfactory receptor cells
Olfactory Epithelium (ordeant, cilia, supporting cell, olfactory receptor cell, basal cell, olfactory nerve axon)
Sections separated by Cribriform plate
Olfactory Bulb (glomerulus, mitral cell, to olfactory tract)
olfactory receptor neurons/cells (ORN)
sensory, smell receptor cells
have non motile cilia - come in direct contact with inhaled odorants and have receptors for different odorants
when odorants bind, the ORNs translate this chemical signal into action potentials - NT onto mortal cell dendrites
ORN - maintained and generated continuously from dividing stem cells
Important to generate new olfactory receptors neurons bc coming in direct contact with anything in periphery
ORN interact with things in the environment and becomes damaged and die we would lose sense of smell at very young age
Have olfactory cilia that acts as their dendrites (receiving signals like a repctors)
Have thin unmyelinated axons that travel through cribriform plate that is a spongy bone
Supporting cells and basal cells
Basal Cell: stem cell replaces olfactory receptor cell
can detoxify chemicals
basal are a type of supporting
Mucus produced by Bowman’s gland
Collection of cells and produces mucus
Mucus helps to trap and neutralize potentially harmful agents
Has various immune cells present
Lots of mucus when sick and can lose sense of smell bc thicken mucus layer and increase mucus production when sick bc increase protection
Thickening harder for odorantes to get to cilia
Olfactory Transduction/Signaling and Steps
Olfactory Signaling → 350 different receptor types - Each binds preferred odorant (perceive diff saints based on combinations of different odorants present in various concentrations)
Order the events of Olfactory Transduction/Signaling
- Odorant molecules inhaled
- Odorant molecules come into contact with olfactory epithelium on roof of nasal cavity
- Odorant molecules bind to olfactory receptor proteins on ORNs
- Activation of Golf from G-protein metabotropic
- Activation of adenylyl cyclase III
- Increase in intracellular cAMP (like activation marker)
- Opening of cAMP gated cation channels
- Sodium and calcium flow into cell through cAMP gated cation channels
- Depolarization of olfactory cilia, reaches threshold (-55 mV)
- Action potentials sent through olfactory nerve axon
- ORN releases neurotransmitters onto mitral cell dendrites in glomerulus
- Mitral cells (present in olfactory bulb) send action potentials through olfactory tract to pyriform cortex and other brain targets
What synapses are located in the olfactory bulb? What are they called?
Within the glomeruli, the olfactory sensory terminals make axodendritic synapses onto the dendritic tufts of both the relay neurons (mitral and tufted cells)
Olfactory bulb is in forebrain
In bulb:
- Olfactory nerve axons synapse with mitral cells (each synapse = glomerulus)
- Each chemical in an odor excites different glomeruli
- Separate individual odorants with each one exciting a different glomeruli
- Combination of excited glomeruli = different smell interpretations
- Each glomerulus contains dendrites of 25 mitral cells, and leaves input from 20,000 ORNs
What cell is located in the olfactory bulb, sending their axons to the brain?
Mitral cells send signals via olfactory tract:
- Principal projection neurons
- Mostly ipsilaterally but subset cross at the midline to allow for some bilateral processing of scent
- Primarily unilateral
Each olfactory nerve projects ipsilaterally/same side to the olfactory bulb
Right bulb process right nostril
Left blub left nostril
The olfactory sensory neurons send their axons directly to synapse within the olfactory bulb. Mitral and tufted cells then relay impulses from the bulb to other brain regions.
What locations in the brain are olfactory signals sent? What functions do these different areas play in olfaction?
Olfactory Receptors → Olfactory Nerve → Olfactory Bulb → Olfactory Tract
Olfactory bulb targets:
Pyriform cortex → Orbitofrontal Cortex which does scent id, decision making, valuation
Olfactory Tubercle → Thalamus which is grand central station for sense
Amygdala (emotion) → Hypothalamus which is memory
Entorhinal Cortex → hippocampal formation
- Signals sent to base of frontal, temporal lobes
Odor identification - Signals sent to limbic system - anything burning
Smoke, burning, skunk – evoke fight or flight - Signals sent to hypothalamus (fight, flight, food, reproduction)
Appetizing foods – evoke salivation
Explain how taste buds are arranged in the papillae on the tongue.
Taste buds are located primarily on the edges of the papillae. They are made of about 50 receptor cells packaged with supportive cells arranged like the slices of an orange. The taste bud has a small opening called the taste pore through which fluids in the mouth come into contact with the receptor cells.
Food chemicals must be dissolved 1st - saliva production to dissolve food digested
Papillae: Projections made up of many taste buds - epithelial specialization - actual visible bumps. Papillae - indivual taste bids are very small cells that have taste recptors and to increase surface area and joine togther in groups called papillae teh acutal bumps felt on tounge and thosands of taste buds clustred togther to make Papillae.
Taste buds contain taste cells: These cells contain receptors for dissolved tastant
Taste Cells and Basal Cells
Taste Cells - graded potentials) (do not send AP instead release NT at ends/bottom of taste cell onto taste fibers or dendrites of whatever cranial nerve is intervading that area) (taste buds made up of taste cell) - translate chemical stimuli (tastants) from food and send info about concentration, identity, and qualities
Taste receptors → concentrated at the apical surface of ciliated gustatory hairs of taste cells
Ciliated
Bind dissolved chemicals → directly bind to different receptors
Contain NT in vesicles
Every 10 days taste buds are renewed and make new taste cells
Bc they are being distributed and impacted all the time with lots of physical contact like burn from hot foods
Basal Cells
Taste stem cells
Replace every 10 days
What are the 5 types of taste? What kind of receptors do they have and what sorts of tastants do they each bind?
Instead, each taste bud contains taste cells containing receptors for multiple types of tastants. Some taste buds contain more of one type than another, but the tongue is not segregated perfectly into the different tastant types.
- Salty not on side or bitter on back of tonge can taste all different tastes throughtout the tounge
- support cells
- no AP –> Following tatse binding - graded potentials
Salt (sodium) - metallic ions - ENaC, NaCl –> electorlyte balance - iontropic (direct ion channels, direct activation, increase in concentraion elicts greater depo) - Na+
Sour- H+ - PKD2L (citric acid, acetic acid) –> acids contain lots of hydrogen ions - iontropic (direct ion channels, direct activation, increase in concentraion elicts greater depo)
Sweet- sugar/glucose - T1R2+T1R3 –> glucose is source of energy and carbs are needed for proper function - metabotropic g protien coupled - D amino acids
Umami- savory/meaty (glutamate) - T1R1+T1R3 –> protien - metabotropic g protien coupled - L amino acids
Bitter- alkaloid - 30 T2R –> indicate foods might be poisonous (ex strychnince) - metabotropic - alkaline more basic
When depolarized → release NT
Explain how sour/salt taste is transduced. Explain how umami/bitter taste is transduced.
Sour - H+ → enter through membrane PKD channels → Depolarization
- Depo with hydrogen ions
Salt - Na+ → enters though membrane Na+ channels (ENaC) →Depolarization
Umami - binds to G protein coupled membrane receptor → opens up channels Ca and activates IP3 which goes to ER allowing relase of intercellualr Ca → IP3 & Ca → opens TRP channels → then depolarization to release NT
Phospholipase C → IP3 → IP3 gated Ca channle in ER →Ca increase into cell which causes depo → opens TRP channels
TRP Channels some on tounge respond to temp
What cranial nerves innervate the tongue and back of the throat?
3 Major receptor nerves innervate the tongue
- Facial Nerve CN7 (2/3 of tounge)
- Glossopharyngeal nerve CN9 (posterior 1/3 of tounge)
- Vagus CN10 (epiglothes and esophagus)
Ends in gustatory cortex of insula
- Limbic areas involved
cranial nerves
- pesudounipolar
- denderite (acts like dendrite bc recives info from tounge) –> peripheral axon –> central axon which sends to brain
- cell body lives in trigeminal ganglion and peripheral. This is near 2nd order neurons called solitatry nucleus in medulla oblongata then to VMP then to insula
Once threshold is reached, cranial nerves axons sends AP
What are the main targets in the brain of the gustatory pathway - taste?
Cranial Nerves VII facial (7) - Taste Buds (ant. two-thirds of tongue)
Cranial Nerve IX glosso (9) - Taste Buds (post. one-third of tongue)
Carnival X vagus (10) - Taste Buds (epiglottis and esophagus)
All three cranial nerves go to nucleus of the solitary tract → goes to hypothalamus (feeding behaviour) and also to → VPM (ventral posteromedial nucleus) of thalamus → Insular of frontal taste cortices (where primary gustory cotrex is) → Amygdala (fear center)
Difference between taste bud and taste cell
A taste bud is a collection of cells grouped inside the bumps on your tongue called papillae. A taste bud includes: Taste receptor cells: Each taste bud has between 50 to 150 taste receptor cells. These cells contain receptors that extend upward inside the taste pore.
Which structure separates the olfactory epithelium from the olfactory bulbs?
a. Olfactory tract
b. Odorants
c. Pyriform cortex
d. Cribiform plate
e. Sphenoid bone
d. Cribiform plate
A scientist creates a knockout rat that has nonfunctional Bowman’s glands. Which functional effect would this most likely have on the rat?
a. Increased ability to maintain temperature and moisture of inhaled air - would actually decrease
b. Inability to generate olfactory receptor neurons continuously - basal cells
c. Increased susceptibility to infection
d. Decreased surface area for odorants to bind to olfactory receptor neurons
c. Increased susceptibility to infection
Listed below are the various components of the olfactory transduction process: 1. Golf G-protein 2. Calcium-activated chloride channel 3. cAMP-gated ion channel(Na and Ca) 4. Adenylyl cyclase III. Which of the following is the correct order in which these components are activated?
a. 4; 1; 3; 2
b. 1; 4; 3; 2
c. 1; 3; 4; 2
d. 1; 2; 4; 3
b. 1; 4; 3; 2
The T2R receptor is responsible for binding tastants in which category? Is it metabotropic or ionotropic?
a. Sweet; Metabotropic
b. Sour; Metabotropic
c. Bitter; Metabotropic
d. Bitter; Ionotropic
e. Sour; Ionotropic
c. Bitter; Metabotropic
A decrease in extracellular H+ would _____ the ability/perception to detect _______?
a. Increase; Sweet
b. Decrease; Sour
c. Decrease; Bitter
d. Increase; Salty
e. Increase; Sour
b. Decrease; Sour
True or False: Tastants do not need to be dissolved (such as in saliva) in order to bind to their receptor.
False
Olfactory signaling is important for survival and housekeeping functions. Which brain area is activated by the smell of appetizing foods?
Hypothalamus
An increase in extracellular alkaloids would ______ the ability to detect ______? Is this receptor metabotropic or ionotropic?
a. decrease; umami; metabotropic
b. decrease; sweet; metabotropic
c. increase; sour; ionotropic
d. increase; bitter; metabotropic
e. increase; bitter; ionotropic
d. increase; bitter; metabotropic
Cranial nerves are an important contributor to numerous functions of the nervous system. Which cranial nerves are important for taste?
Select all that apply:
a. Cranial nerve 5 (Trigeminal nerve)
b. Cranial nerve 7 (Facial nerve)
c. Cranial nerve 8 (Vestibulocochlear nerve)
d. Cranial nerve 9 (Glossopharyngeal nerve)
e. Cranial nerve 10 (Vagus nerve)
f. Cranial nerve 12 (Hypoglossal nerve)
b. Cranial nerve 7 (Facial nerve)
d. Cranial nerve 9 (Glossopharyngeal nerve)
e. Cranial nerve 10 (Vagus nerve)
Miracle Berry – Predict the Mechanism
Miraculin is a glycoprotein (a protein that has a carbohydrate group attached to the polypeptide chain) that has been isolated as the potent component of the Miracle Fruit that alters taste perception by binding to sweet receptors on the tongue.
Given that miraculin binds to sweet receptors, and using your knowledge of how it changes taste, what is your prediction of its mechanism? Try to come up with a few possible theories!
The sweet taste receptor is a heterodimer consisting of T1R2 and T1R3
The T1R2-T1R3 taste receptors respond to a variety of sugars, sweeteners and small proteins.
It has been hypothesized that the way that the miracle berry works is that miraculin binds directly to the sweet taste receptor T1R2-T1R3.
While it can bind to the receptors under neutral pH conditions, miraculin only activates the receptor in the presence of an acid
The receptor undergoes a structural change in the presence of protons (H+), causing the carbohydrate portion of the miraculin molecule to bind to the sweet receptor site, leading to a pH-dependent (between pH 4.8 and 6.5) activation of human sweet taste receptor cells.
Which cells of the olfactory system send action potentials through the
olfactory tract to targets in the brain? Where are their cell bodies
located?
a.Olfactory receptor neurons; glomeruli
b.Olfactory receptor neurons; olfactory epithelium
c.Basal cells; olfactory epithelium
d.Mitral cells; olfactory bulb
e.Mitral cells; glomeruli
d.Mitral cells; olfactory bulb
A mouse strain you are working with lacks the G olfactory protein. How
will lack of this protein affect the sense of smell in the mice?
a. Inhibits the opening of Na+ ion channels
b. Prevents binding of the odorant to the sensory receptor cell cilia
c. Prohibits starting of AP in mitral cells due to increased release of glutamate from
olfactory sensory cells
d. Results in constant opening of voltage gated Ca2+ channels
e. Prohibits the starting of AP in mitral cells due to lack of AP in sensory receptor
neurons
f. Inhibits the production of cAMP
g. Start more action potentials in neurons in the temporal lobe olfactory cortex
h. A and E and F
i. All of these
h. A and E and F
A mouse strain you are working with lacks the G olfactory protein. What do
you predict to be the phenotype(symptoms) of this mouse strain when food,
new mice and new toys are placed in their cages out of sight?
a. The mice will find and approach all new items based on smell but will not
be able to see them
b. The mice may be able to find some of the new things but not all of them
c. The mice will not find or approach any of the new items
d. The mice will find and approach the new mice, food and toys in the cage
e. The mice will not react to the sounds of the new items in the cage
c. The mice will not find or approach any of the new items
After a sweet tastant binds to its sweet receptor, what
follows the activation of the G-protein?
a. Activation of adenylyl cyclase III
b. Activation of IP3 and increase of intracellular calcium
c. Direct opening of TRPM5 channel by activated G-protein
d. Opening of cAMP-gated cation channels
e. Release of calcium from the sarcoplasmic reticulum
b. Activation of IP3 and increase of intracellular calcium
Projections from the pyriform cortex to other brain regions allow olfaction to influence which other behavior(s) and/or function(s)? (Select all that apply:)
a.Appetite
b.Memory
c. Vision
d.Fight or flight
e.Reproduction/attraction
a.Appetite
b.Memory
d.Fight or flight
