Are taste buds taste receptors?
NO - receptors are located within the taste buds
Where are the taste buds located?
What are the 3 types of papillae?
Fungiform, circumvallate, foliate
Where are the fungiform papillae located?
Anterior 2/3 of the tongue (general sensory = V3, taste = facial)
Where are the circumvallate papillae located?
At the back of the tongue (form the V)
Where are the foliate papillae located?
On the sides of the tongue; cross the border between the fungiform and circumvallate papillae
What is the relative concentration of fungiform papillae to circumvallate papillae on the tongue?
Lots of fungiform, not many circumvallate
Where are taste receptors located?
In the taste buds (which are in the papillae)
Are taste receptors replaced at all?
Yes, even faster than olfactory receptors are
What contains the actual taste receptors?
In the end of microvilli (which arise from basal cells)
Do taste receptors respond to only certain tastes?
No - respond to multiple tastants
What CNs do taste?
Anterior 2/3 = chorda tympani of 7; posterior 1/3 = 9
Describe the connections between taste receptors and afferent fibers.
Afferent fibers synapse with >1 bud and each bud synapses with >1 afferent fiber
What CNs do general sensory to the tongue?
Anterior 2/3 = V3; posterior 1/3 = 9
What CN controls all the tongue muscles?
12 - hypoglossal
What muscle is the primary tongue mover?
What branchial arch(es) does the tongue arise from?
Arches 1-4 (that's why so many CNs innervate it...)
What is CN7 taste pathway?
Chorda tympani -> geniculate nucleus -> nucleus of solitary tract ->via central trigeminal tract to VPM of thalmus -> gustatory cortex (insula) -> orbitofrontal (IDing taste) and limbic system (emotional/instinctional relationships)
What are the final synapses for taste in the CN7 pathway?
Orbitofrontal (IDing taste) and limbic system (emotional/instinctional relationships)
What nerves from CN7 innervate the tongue?
Chorda tympani (anterior 2/3) and superior petrosal (soft palate)
Is taste contralateral or ipsilateral?
What nerve innervates the posterior 1/3 of the tongue?
Lingual branch of CN9
What is the taste pathway for CN9?
Lingual nerve -> inferior ganglion of IX -> solitary nucleus ->via central trigeminal tract to VPM of thalamus -> gustatory cortex (insula) -> orbitofrontal cortex (IDing taste) and limbic system (emotional relationships)
What is the taste pathway for CN10?
Superior laryngeal nerve -> inferior ganglion of X -> solitary nucleus ->via the central trigeminal tract to the VPM of the thalamus -> gustatory cortex (insula) -> orbitofrontal (IDing taste) and limbic system (emtional relationships)
How does chemotherapy affect taste?
Changes the way you taste -- not understood why but it pretty much universal
What is ageusia?
Absence of taste
What are the 3 cell types of taste epithelium?
Supporting cells, basal cells and receptor cells
What do basal cells do?
Serve as precursors to receptor cells (just like in olfactory epithelium)
Describe the physiology of a taste receptor cell.
Receptor cells send out microvilli into taste pore and that's where the receptors are
Are taste receptor cells neurons?
NO! -- they are specialized epithelial cells (in olfactory the receptors are neurons)
Which are the biggest papillae (but fewest in number)?
What papillae best sense bitter taste?
Circumvallate (carried by CN9)
What papillae best sense sour taste?
Foliate (carried by CN9)
What papillae best sense sweet and salty?
Fungiform (carried by CN7 -- chorda tympani)
How do chemical taste signals from the receptors transduce into an action potential?
Binding results in depolarization of taste receptor membrane, leading to actions potentials in afferent nerves innervating that portion of the tongue (cAMP or IP3 pathway)
What is the cross-fiber pattern code?
Each taste fiber responds best to 1 stimuli but also repsonds to a lesser extent to other stimuli (taste receptors receives info in a pattern of responses)
Where is the solitary nucleus located?
Where is the primary gustatory cortex?