Physiology of Gustation and Olfaction Flashcards
Sour taste stimulated by what ions and release what NT
H+ ions
Serotonin
Salty taste stimulated by what ions and release NT
Na+ binding ENaC
Serotonin
Sweet taste stimulated by what molecules and release what NT
Sugars binding GPCRs
ATP
Umami taste stimulated by what molecules and release what NT
Glutamate binding mGluR4 GPCR
ATP
Bitter taste stimulated by what molecules and release what NT
Various compounds binding GPCR
ATP
Taste bud cells
Specialized epithelial cells
Chemosensory transduction is initiated in apical domain and electrical signals generated in basal domain
Taste receptor proteins located on microvilli on apical surface
Olfactory neurons
Bipolar neurons that release glutamate as primary NT
Odorants bind and activate odorant specific G protein which activates adenylate cyclase and eventually leads to Ca2+ gated Chloride channels opening
Sensitization to a smell
When pleasant or pungent odors are presented, the odorant receptor itself can become phosphorylated, which modifies its sensitivity to odorants
This plays a role in perceived changes in awareness of smells
Sensitivity of the CNGC (cyclic nucleotide gated channel) to cAMP will also decrease which reduces cation influx and assists in sensitization
Ca binding calmodulin will cause reduced sensitivity for the channel to cAMP
Bitter taste ligands affinity
Bitter taste can be associated with poisons, and therefor the ligands that stimulate the GPCRs for bitterness bind with very high affinity
Sweet tastes and analgesics
Sweet tastes can be used as an analgesic for newborns during minor, painful procedures. It will typically calm the child and reduce heart rate for several minutes
It is speculated that sweet taste causes beta-endorphin release, activating endogenous opioid system
Hiding bitterness in drugs
Sodium salts can be added to suppress the bitter taste at the level of the receptor.
Sugars suppress the sense of bitterness at the cognitive level
Processing of taste in nucleus of the solitary tract
Receives multiple sensory inputs from vagus nerve that relays info about the viscera
Early site of gustatory and visceral info
Processing of taste in ventral posterior medial nucleus of the thalamus
Relay station for taste perception
The discriminative aspects of taste are processed here
Gustatory cortex
Consists of the insular taste cortex, operculum of frontal lobe, post central gyrus
Processing of taste in the hypothalamus and amygdala
Amygdala gives emotional context and memories of eating
Hypothalamus integrates mechanisms of eating such as hunger
Interplay b/w eating and the calming effects of food take place in the limbic and reward system
Processing of taste in the orbitofrontal cortex
This area integrates visual, somatosensory, olfaction and gustatory stimuli to collectively appreciate the flavor of food
Flavor does not = taste, it requires the additional senses listed above
Granular cells in olfactory mucosa and bulb
Local interneurons that release GABA and increase specificity of signal
Mitral cells in olfactory mucosa and bulb
Project to the olfactory tract along with tufted cells
Synapse in the olfactory glomerulus with olfactory receptor neurons
Periglomerular cells in olfactory mucosa and bulb
Local interneurons that release GABA and increase specificity of signal near the olfactory glomerulus
Olfactory neurons
Synapse onto glomeruli and release glutamate
Anterior olfactory nucleus
Relay station to ipsi and contralateral cortices
Poorly understood
Piriform cortex and lateral hypothalamus
Control of appetite and how olfactory input influences appetite and hunger
Piriform cortex and medial orbitofrontal cortex
Integration of sight, smell and taste of food
Appreciation of the flavor of food
Anterior cortical amygdaloid nuclei
Emotional learning, olfactory fear conditioning
Periamygdaloid cortex
Integration of the emotional aspect of food as elicited by odor
Entorhinal cortex and hippocampus
Memory formation and how olfactory input facilitates both memory and recall
Connections within limbic system and entorhinal cortex are responsible for the highly evocative experience of memory upon odor sensation
Parkinsons and olfactory neurons
Olfactory neurons are among the first to demonstrate pathology, sometimes years before a motor deficit is manifested
Olfactory testing as a biomarker for neurodegenerative diseases is becoming increasingly common practice
