Physiology of Olfaction and Gustation Flashcards
What is the loss of sense of smell called?
Anosmia
What is the loss of sense of taste called?
Aguesia
What are tastants?
Chemical compounds that bind to taste receptors and impart the primary flavor categories
What are odorants?
Chemical compounds that bind odorant receptors and impart odor
What tastants are associated with ion channels and serotonin release?
Sour and salty
What tastants are associated with GPCRs and ATP release?
Sweet, umami, bitter
What compound binds GPCRs for umami taste?
Glutamate binds mGluR4
What happens after the tastant binds the GPCR or enters the ion channel?
Intracellular calcium release facilitates synaptic vesicle fusion with the basal membrane to release NTs onto the primary sensory neuron to induce an AP
How do taste cells and olfactory cells differ?
Taste cells are specialized epithelial cells
Olfactory cells are bipolar neurons that release glutamate
What happens after an odorant binds to a receptor molecule?
A specific G protein is activated that activates adenylate cyclase, resulting in cAMP generation and then an influx of Na+ and Ca2+. This results in depolarization which causes calcium-gated Cl- channels to open. Cl- leaves to further depolarize the cell
What happens to reduce odorant receptor potential?
cAMP is broken down and calcium binds to calmodulin. The receptor can also be phosphorylated to decrease sensitivity to odorants (happens when you “get used to” a smell)
What do sweet tastes signal to the brain?
Presence of carbs aka energy source
What do salty tastes govern?
Intake of Na+, essential for maintaining water balance and blood circulation
What do umami tastes signal to the brain?
Protein content (glutamate and other amino acids)
What do sour tastes signal to the brain?
Dietary acids, also indicates spoiled food
What do bitter tastes signal to the brain?
Guards against consuming poisons
Which taste has the highest binding affinity to its receptors?
Bitter tastes
Why do adults tend to add more salt and spices to food than children do?
Taste and smell sensitivity declines with age :(
When do sensation of smell and taste begin?
In utero to prime the fetus to tastes in the external environment
What can be used to reduce procedural pain in infants? How does this work?
Sucrose/sweetness - only for single painful events. Believed to be due to induced beta-endorphin release activating the endogenous opioid system
How can bitter taste be masked?
Sodium salts at the level of the bitter-receptor
Sugars at the cognitive level
How is the nucleus of the solitary tract involved in processing of taste?
Early site of gustatory and visceral information: receives inputs from Vagus N.
How is the VPM of the thalamus involved in the processing of taste?
Relay station for taste perception, processes discriminative aspects of taste
What makes up the gustatory cortex?
Insular taste cortex
Operculum of frontal lobe
Post-central gyrus
How are the hypothalamus and amygdala involved in the processing of taste?
Amygdala- emotional context to eating, memories of eating
Hypothalamus- homeostatic mechanisms like hunger
How is the orbitofrontal cortex involved in the processing of taste?
Integrates visual, somatosensory, olfaction, and gustatory stimuli to collectively appreciate the flavor of food
How is the anterior olfactory nucleus involved in the processing of smell?
Relay station to ipsilateral and contralateral cortices, poorly understood
How are the piriform cortex and lateral hypothalamus involved in the processing of smell?
Control appetite and how smells influence appetite/hunger
How are the piriform cortex and medial orbitofrontal cortex involved in the processing of smell?
Integrate sight, smell, and taste of food to appreciate flavor of food
How is the anterior cortical amygdaloid nuclei involved in the processing of smell?
Emotional learning and olfactory fear conditioning
How is the periamygdaloid cortex involved in the processing of smell?
Integrates emotional aspect of food as elicited by odor
How are the entorhinal cortex and hippocampus involved in the processing of smell?
How olfactory information facilitates both memory and recall, responsible for highly evocative experience of memory upon odor sensation
What part of the taste bud is involved in chemosensory transduction?
the Apical domain
Basal domain—>electrical signaling
