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.
