Olfaction and Gustation Flashcards
5 taste categories and what they respond to
Bitter—poisons, coffee Salty—salt Sweet —sugar, honey Sour—citrus, vinegar Umami—glutamate
Receptor potentials of taste cells are usually depolarizing, which involves opening of voltage-gated ____channels and NT release, which depends on cell type.
Sour and salty trigger release of NT ______, while sweet, bitter and umami trigger release of ______
Calcium
Serotonin; ATP
3 destinations of ATP released from sweet, umami, and bitter receptor cells
- Post-synaptic primary gustatory neurons
- Pre-synaptic salty/sour receptor cells to stimulate serotonin release
- Autocrine signaling
Serotonin released from salt/sour receptor cells stimulates ______ neurons
Post-synaptic primary gustatory neurons
Receptor potentials of taste cells are usually depolarizing, which involves opening of voltage-gated ____channels and NT release, which depends on cell type.
Sour and salty trigger release of NT ______, while sweet, bitter and umami trigger release of ______
Calcium
Serotonin; ATP
3 destinations of ATP released from sweet, umami, and bitter receptor cells
- Post-synaptic primary gustatory neurons
- Pre-synaptic salty/sour receptor cells to stimulate serotonin release
- Autocrine signaling
Serotonin released from salt/sour receptor cells stimulates ______ neurons
Post-synaptic primary gustatory neurons
Mechanisms by which 5 taste qualities are transduced in taste cells
Sweet, umami, bitter via GPCR
Salt via ENaC
Sour via proton-sensitive channel
Sweet tastants activate GPCRs, activating PLC-IP3 pathway and increasing intracellular Ca, eventually activating _____ which is what results in depolarization and release of ATP through ____ channels and NT release
TRPM5; PanxI
Umami has the same pathway as the sweet and bitter tastants, but activates a specific GPCR, the ____
mGluR4
Which tastant binds with highest affinity?
Bitter - for poison detection
Taste buds are innervated by special visceral afferent neurons including:
Anterior tongue: Chorda tympani branch of facial nerve with cell bodies in the geniculate ganglion and termination in the ____________
Posterior tongue: lingual branch of glossopharyngeal n. with cell bodies in petrosal ganglion and termination in the ________
Epiglottis: superior laryngeal branch of vagus n. with cell bodies id nodose ganglion and termination in _________
Nucleus tractus solitarius (gustatory area) x3
In the ascending taste pathway, secondary sensory neurons cell bodies are in the nucleus tractus solitarius, which ascends to synapse on tertiary sensory neuron cell bodies in the _____ of the thalamus. These neurons ascend through the posterior limb of the internal capsule and terminate in the gustatory cortex which is made up of the _____, ____, and _____
VPM
Postcentral gyrus, frontal operculum, and insular cortex
Additional taste interpretation takes place in the ____ cortex which integrates taste, olfaction, and visual cues regarding food (appreciation of flavor, food reward, and control of feeding)
Additional taste responsive cells are located in the ___ and ____ which are involved in emotional context and memories of taste
Orbitofrontal
Amygdala; hypothalamus
In what part of the ascending taste pathway are there medullary reflex arcs for salivating, swallowing, etc?
Nucleus tractus solitarius
Olfactory receptors are GPCRs, specifically _____ which stimulates AC, increasing cAMP, and opening ______ channels, leading to cation influx and membrane depolarization
G[olf]; cyclic nucleotide gated channels (CNGC)
What happens to sensitivity of the CNGC to cAMP as odorant stimulation persists?
It decreases, reducing cation influx, or it is inactivated by receptor phosphorylation
Basically desensitizing you to the odor
One oflactory neuron expresses the same odorant receptor on all of its cilia. Then the projections of similar odorant receptors are collected into one ____
Glomerulus
How do we detect ~12 mill odors with only ~350 different odorant receptors?
One odorant can stimulate more than one type of OR
The combinations of different OR stimuli act like a “signature” of that odorant
[concentration of odorant also makes a difference, odorants smell different at different concentrations]
Cell types of olfactory bulb
Mitral cells
Granule cells
Periglomerular cells
Olfactory neurons synapse onto glomeruli and release ______
Periglomerular cells are local interneurons and release ______, increasing specificity of the signal
_____ cells and tufted cells will project to the olfactory tract
Granular cells are local interneurons and release ____, further increasing specificity of odorant signal
Glutamate
GABA
Mitral
GABA
T/F: the olfactory system is the only sensory system that does not route through the thalamus before connecting to the cortex
True
Components of olfactory cortex
Anterior olfactory nucleus Olfactory tubercle Piriform cortex Anterior cortical amygdaloid nuclei Periamygdaloid cortex Lateral entorhinal cortex
The _____ _______ nucleus is a relay station for olfactory info to ipsilateral and contralateral cortices and it is poorly understood
Anterior olfactory
The piriform cortex projects to the ____ ____ and functions in control of appetite and hunger
Lateral hypothalamus
The piriform cortex also projects to the ______, then the _______ to control integration of taste, sight, and smell — thus the appreciation of flavor of food
Thalamus; medial orbitofrontal
Which olfactory cortex functions in emotional learning and olfactory fear conditioning?
Anterior cortical amygdaloid nucleus
Which olfactory cortex functions in integration of emotional aspects elicited by odor?
Periamygdaloid cortex
The entorhinal cortex projects olfactory info to the ____ which is important in memory formation
Hippocampus
What is the difference in Na+ gradient and permeability in olfactory neurons vs. taste cells?
Olfactory neurons exhibit fixed Na+ gradient and shifting permeability
Taste cells exhibit fixed permeability and shifting Na+gradient
Perception of flavor requires gustatory input and olfactory input as well as somatosensory info from the mouth, this information is organized by the ____ ___ cortex
Medial orbitofrontal cortex
T/F: loss of taste is often an olfaction problem
True
How/why does olfaction strongly influence memory?
The connections in the temporal lobe overlay those of the hipposcampus and amygdala, components of the limbic system, which is important in setting mood and emotional behavior
These are the areas responsible for associating emotional response with odors. Presumably these areas are also responsible for highly evocative experience of memory upon odor sensation
