Flashcards in Chemosensation 2 Deck (31)
List the 5 primary taste qualities and for each indicate whether sensory transduction involves ion channels or G-protein coupled receptors
1. Salty or Sour: ion channels (since are ionic stimuli).
2. Sweet, bitter, umami (glutamate): metabotropic receptors, G protein linked (more complex stimuli).
All taste buds in the pharynx, extreme posterior tongue, esophagus, and epiglottis are innervated by
3 types of gustatory papillae
1. Fungiform papillae
2. Foliate papillae
3. Circumvallate papllae
1. located in the anterior end of the tongue
2. innervated by the facial nerve.
1. on the side of the tongue
2. innervated by the facial nerve.
1. located at the posterior end of the tongue
2. innervated by the glossopharyngeal nerve.
Central taste pathway:
1. primary afferents from tongue run in the facial, glossopharyngeal, and vagus nerves.
2. When axons enter the CNS they synapse on second order neurons in the rostral area of the ipsilateral Nucleus of the solitary tract (NST).
organized orotopically in the medulla. There is a map of the oral cavity on the nucleus so anterior parts of mouth are anterior in the nucleus.
1. 2nd order cells (in rostral portions of NST) send axons bilaterally to the medial part of the ventrobasal thalamus
2. The thalamic neurons then send their axons in to insular cortex.
Conscious appreciation of taste:
from pathway to insular cortex
where integration of taste and smell leads to perception of FLAVOR!!!
Secondary gustatory cortex is located
in the orbitofrtonal surface
Secondary gustatory cortex receives projections from
1. the primary gustatory area located on the interior insula
2. olfactory insula areas.
Subconscious taste pathways:
NST also relays taste info to hypothalamus and amygdala for food intake regulation and visceral reactions to ingested foods.
NST has reflex connections to
nuclei in the brainstem for
1. gagging (nuc ambiguous),
2. swallowing (nuc ambigusus, hypoglossal nuc.)
3. salivation (sup and inf salivatory nuc).
Each odorant stimulates a number of receptors.
1. Info on odor identity is NOT coded by labeled line or localized to a single glomerulus.
2. Odor identity is distributed in wide areas of the glomerular layer so it entails PATTERN RECOGNITION!!!
Primary principle of encoding odor quality = .
odor-specific map of glomeruli in olfactory bulb
Axons of olfactory neurons cross the_____ and converge on ____.
1. spherical neuropil structures at the outer layer of the olfactory bulb.
2. 1000 axons from single olfactory neuron make excitatory synaptic connections w/ apical dendrite of 2-25 mitral cells at each glomeruli.
Olfactory receptor neurons expressing the same olfactory receptor protein project their axons _____
into the SAME glomerulus.
Convergence of axons that stem from receptor neurons w/ same chemical specificity is basis for _____
ability of olfactory system to recognize structurally dissimilar odorants.
Olfactory cortex: consists of:
lateral olfactory gyrus and part of the uncus
Other major olfactory connections with limbic system:
2. olfactory tubercle
3. entorhinal cortex.
Gives subconscious regulation of homeostasis, circadian, reproductive and other biological activity patterns.
Amygdala + olfactory tubercle are interconnected with
feeds into hippocampus, major player in storage and retrieval of MEMORIES!
Olfactory cortex is divided into several areas including:
1. the piriform cortex
2. accessory olfactory nucleus
3. olfactory tubercle
Piriform cortex projects to:
association area for olfactory and taste information, gives us the conscious appreciation of smell!!!
Output of olfactory bulb
1. projects directly to cortex, NOT through thalamus
axons of output cells from the bulb collect into the
lateral olfactory tract