L1: Olfaction and taste Flashcards
Humans can discriminate how many olfactory stimuli?
Over 1 trillion
What type of neurons are olfactory neurons?
Bipolar with dendrites that form cillia and axons that terminate in the olfactory bulb.
What type of receptor is the odor receptor?
GPCR
Where are olfactory receptors located?
In the olfactory epithelium
How many types of olfactory receptor are expressed by an olfactory nerve?
One type
How many odorants can each olfactory nerve respond to?
Single or multiple
What types of mammals have trace-amine-associated-receptors and which ones have vomeronasal organs?
All mammals have TAAR and only non-ape mammals have vomeronasal organs (not humans)
What type of signal transduction is used by TAAR?
Golf/cAMP
What type of odorant is detetected by TAAR and vomeronasal organs?
Pheromones
How is initial olfactory adaptation mediated?
Increased Ca binds to the Ca binding protein which desensotizes the CNGA channel
How is short term olfactory adaptation mediated?
Ca binds to calmodulin protein kinase II which desensitizes adenylyl cyclase
How is long term olfactory adaptation mediated?
Ca increases NO production which stimulates guanylate cyclase to produce cGMP which causes influx of Ca through CNGA channel leading to further desensitization of CNGA and AC
Where do axons of the olfactory neurons synapse?
Glomeruli of the olfactory bulb
HOw many ORN axons are received by a glomeruli?
thousands
How many types of ORN information can one glomeruli receive?
One
What increases odor discrimination at the glomeruli and mitral later?
Lateral inhibition
What are the layers of the olfactory bulb?
- Olfactory nerves
- Glomeruli
- External plexiform layer
- Mitral cell layer
- Granule cell layer
Where do mitral cells send information?
- anterior olfactory nucleus
- Olfactory tubercule
- Piriform cortex
- Amygdala
- Entorhinal cortex
Where does odor perception and discrimination happen?
Obitofrontal cortex (must go through thalmus)
Where does odor induced fear signaling happen?
Amygdala-piriform boundary
Where fo the emotional, motivational, physiological and behavioral aspects of motivation happen?
Amygdala and hypothalmus
Where are taste cells located?
- Tongue
- Pharynx
- Palate
- Epiglottis
- Upper third of the esophagus
What is the anterior 2/3 of the tongue innervated by?
Chorda tympani branch of the facial nerve via the geniculate ganglion
What is the posterior 2/3 of the tongue innervated by?
The lingual branch of the glossopharyngeal via the petrosal ganglion
What nerve is the pharynx innervated by?
The superior laryngeal branch of the vagus via the nodose ganglion
What type of taste buds are found on the anterior 2/3 of the tongue?
Fungiform and filiform
What type of taste buds are located on the posterior portion of the tongue?
Circumvallate and foliate
What are tatse cells embedded in?
Papillae
What is the tastant for sweet and what is its threshold?
Sucrose 20mM
What is the tastant for salty and what is its threshold?
NaCl 10mM
What is the tastant for sour and what is its threshold?
Citric acid 2mM
What is the tastant for bitter and what is its threshold?
Quinine 8 mM
What is the tastant for Umami and what is its threshold?
Glutamate 100 mM
What is the function of type 1 taste cells?
Support and putative salt sensor
What is the function of type II taste cells?
Sweet bitter and umami
DO NOT form conventional synapses
What is the function of type II taste cells?
Sweet bitter and umami
DO NOT form conventional synapses
What is the function of type III taste cells?
Respond to sour stimuli, form prominent synapses with afferent nerve fibers and release serotonin and ATP
What type of cells are basal cells and what is their turnover rate?
Progenitor cells with a 10 day turnover rate
What is the numerical distribution/ order of abundance for taste cells?
Type I> Type II> Type 3
What taste receptors are for umami?
T1R1 and T1R3
What are the taste receptors for sweet?
T1R2 and T1R3
What taste receptors are for bitter?
~30 T2Rs
What taste receptor are for salty?
ENaC
What tase receptors are for sour?
PKD2L1
What cells are responsible for salt attraction?
Type I
What cells are responsible for salt aversion?
Type III
What inhibits salt attraction?
Amiloride
What does PKD2L1 knockout do?
Reduces sour sensing
What type of fibers are intergemmel nerves?
Gustatory nerves
What type of nerve is perigemmal fibers?
Somatosensory nerves
What is responsible for chemisthesis?
Perigemmal fibers (trigeminal nerve)
Where is the P2X2/3 receptor found?
Intergemmal fibers
How is ATP released form type II taste cells?
Non-vessicle via CalHM1
How are GABA, 5HT and ATP released from type III cells?
Via vesicles
What is the nociceptor for capsacin?
TRPV1
What is the nociceptor for wasabi?
TRPA1
What is the nociceptor for menthol and cold?
TRPM8
What is the main somatosensory nerve of the head?
Trigeminal
Where does the CNS project to modulate taste and defensive reflexes?
Sp5 in the medulla
What is each taste cell innervated by?
Primary gustatory fibers
How many taste buds are innervated by each primary gusatory fiber?
Many
What type of coding do specialist affarent gustatory fibers have?
Line labeled coding
What type of coding do generalist affarent gustatory fibers have?
Combinatorial coding
What types of information are extracted from tastants?
Quality
Intesity
Hedonic Value
What tastants have no overlap?
Bitter and sweet