Taste and Smell Flashcards
What are the 4 categories of smell cells ?
4 Categories of cells :
1- Visceral chemoreceptors - for O2 ..
2- Gustatory receptors
3- Olfactory receptors
4- Chemosensitive endings - for the common chemical sense (papper and .. )
perception of falvour comes from _ , _ , _ , and integrated in ____ cortex
But perception of flavour comes from:
chemical sensation of taste buds +
stimulation of olfactory bulb by food vapours +
stimulation of nerve endings (eg in trigeminal) in the mucous membranes in mouth and nose (detects pungent, temp, .. )
integrated in the orbitofrontal cortex
Tongue is mainly a muscle but surface is covered with bumps and folds called _____________ .
Tongue is mainly a muscle but surface is covered with bumps and folds called papillae.
What are the three types of papillae that have taste buds ?
Most papillae do not contain taste buds but three types do:
fungiform papille (mashroom-shaped” : 200 - 300 , anterior 2/3 on ti, 3-5 tastebuds inside.
foliate papillae (leaf-like) 20 folds on posterior sides of tongue, each has 100-150 taste buds in the fold
Circumvallate papillae (surronded by wall) V-shaped line 2/3 back on tongue, each of the 9 papilla is surrounded by groove with 250 taste buds in each groove ..
taste buds are innervated by which cranial nerves ?
Taste buds are innervated by CNs IX (circumnvallate and posterior foliate) and VII (anterior foliate and fungiform)
which cranial nerves that serve in epithelial cells and what do they serve ?
For epithelial cells CN V serves general sensation on the common chemical sense for anterior 2/3 of tongue; CN IX does same thing for posterior 1/3
Also some tastebuds on ______ and _____ but are probably for reflex retain to “bad” taste and aren’t consciously processed.
Also some tastebuds on epiglottis and soft palate but are probably for reflex retain to “bad” taste and aren’t consciously processed.
Each taste bud contains many taste cells: some are _________ others are __________ that developed neuron-like properties and called ___________
Each taste bud contains many taste cells: some are supporting glialike others are modified epithelial cells that developed neuron-like properties : taste receptor cells
Each taste receptors cell has __________ through which _________ protrude to interact with the chemical to be tasted.
Each taste receptors cell has a pore through which microvilli protrude to interact with the chemical to be tasted.
Taste receptor cells generate receptors potentials in response to appropriate taste stimuli, Make chemical synapses onto __________ , some can produce action potentials when receptors potential is sufficiently depolarising
Taste receptor cells generate receptors potentials in response to appropriate taste stimuli, Make chemical synapses onto gustatory nerve, some can produce action potentials when receptors potential is sufficiently depolarising
Unlike neurone, taste receptor cells regenerate continuously.
Unlike neurone, they regenerate continuously.
explain the mechanism by which taste receptors cells respond to the 5 tastes
Salty - transducers NaCl into and electrical signal easily because it opens Na+ channels = depolarisation
Sour - acides transduce in two ways: weak acides diffuse across membrane, strong acids depolarise it.
Sweet and Umami - activate metabotropic (G-coupled) mechanisms.
Bitter - similar to sweet and umami (30 G-coupled messenger) , danger?
Describe the pathway of smell:
which CN involved ? which brainstem neclues involved
Tongue to solitary nucleus (CN VII IX X)
2nd order gustatory neurons located in solitary nucleus, do two things:
- Participate in reflex activities like salivating , swallowing coughing via motor nuclei
- project sensory info through thalamus to cortex (all ipsilateral)
Solitary tract to central tegmental tract in pons.
Pons to thalamus (VPM nucleus)
Thalamus to prinart gustatory cortex: insula, frontal opercula
Primary gustatory cortex to
1) association cortex: orbitofrontal cortex where it is integrated with olfaction and other info and
2) amygdala
Amygdala to hypothalamus and limbic system.
what ways could coding for taste happen ?
spatial localisation of food and in mouth is not important for the sense of favours , so where taste buds are doesn’t code for this.
Instead gustatory and olfaction work together to code the taste stimuli (separate and in mixture). Coding could happen in two ways:
- Labled-line coding - could have thousands of receptors types for every kind of food stimulus out there.
- Across-fiber coding - could have patterns of activity in large populations of neurons with sensitiveness to multiple food stimuli.
Gustatory system actually uses both: at taste receptors cell level only responds to one of the taste, but nerve can innervate different taste buds on different papillae and thus can respond to more than one taste (although on average has a taste preference “tuning” : CN VII likes sweet or salty, .. )
Trigeminal nerve fibers have sensory endings in the ____________ and is responsible for detaching ____________ (ammonium).
Trigeminal nerve fibers have sensory endings in the olfactory epithelium and is responsible for detaching noxious doors (ammonium).
