Neuro olfaction/ taste

what does sense of taste help us determine

source of calories, electrolytes, and proteins

what are the 3 types of papillae?

• fungiform (mushrooms)

• circumvallate (pimples)

• foliate (ridges)

how much of the tongue is made up by foliate papillae, where is it usually found, and what nerves are connected to it?

• 25%

• postereolateral

• 7 and 9

how much of the tongue is made up by circumvallate papillae, where is it usually found, and what nerves are connected to it?

• 50%

• rear of tongue

• 9

how much of the tongue is made up by fungiform papillae, where is it usually found, and what nerves are connected to it?

• 25%

• anterior 2/3 of tongue

• 7

what cranial nerve also has role in taste outside of 7 and 9?

10

what are the 3 types of taste bud cells

• glial like to clear transmitters

• chemosensory for sweet, bitter, umami, and salty (no vesicles, just ATP transport)

• chemosensory for sour (uses vesicles)

what channel is specific to salty flavor?

sodium channel

what channel is specific to sour taste?

H+ sensitive TRP channel

what receptor is specific to sweet flavor?

T1R2 and T1R3 receptors

what receptors/ channels are specific to umami flavor?

T1R1 and T1R3 receptors and also TRPM5 channel

what receptors/ channels are specific to bitter flavor?

T2R receptor and TRPM5 channel

what is the pathway for a taste?

tastebud > afferent axon > brain stem > thalamus > cerebral cortex > brodmanns area 43

what is being narrowly tuned vs broadly tuned to a taste?

narrow- shows 1 tastin in 1 cell

broad- shows multiple tastins in multiple cells

what is labeled line coding?

a neuron is specially dedicated to a specific taste (narrowly tuned)

what is across neuron pattern?

a form of population coding where multiple neurons are used for a taste

what is temporal coding?

when the gustatory system relys on timing of AP’s and itme course of firing rate changes

what nerve is the olfactory bulb?

nerve 1

what will the basal cell turn into?

olfactory receptor cells

what does a supporting cell transform into?

mucus

what is the purpose of the cilia in olfactory cells?

a place for the oderant to bind to trigger the pathway

oderants interact with _____ found in an ______ ____

olfactory receptor neurons (ORNS) ; epithelial sheet

what is an ORN?

olfactory receptor neurons (bipolar)

• only neurons in the olfactory epithelium because its the CNS

what is the secondary messenger to the oderant molecules?

cAMP, which opens the Na and Ca channels to open the Cl channels leading to membrane depolarization

what is the most common exchanger present to repolarize and reset the olfactory membrane?

an Na/ Ca exchanger to decrease cAMP levels after activating phosphodiesterase

what clears out oderants present in the receptor?

arrestin

what is the primary neurotransmitter in the olfactory bulb?

glutamate

what is a glomeruli?

most distinctive feature of the olfactory bulb

• accumulations of neurophil (axons, dendrites, glial)

what are the 3 classes of local circuits neurons?

external tufted, periglomerular, and short axon

• all play a role in olfactory bulb plasticity

what are the characteristics of external tufted cells?

glutamatergic and excitatory

what are the characteristics of periglomerular cells?

GABAergic and inhibitory

what are the characteristics of short axon cells?

dopaminergic and modulatory

what are some characteristics of the olfactory bulbs projections onto the olfactory cortex

• do not pass through thalamus (unqiue)

• some projections synapse onto the frontal lobe

• allows for odor discrimination, emotion, and memory

what is an olfactory map

orderly arrangement of neurons responsive to particular odor can be organized into spacial maps

how is temporal coding important in the olfactory system?

timing of AP’s may be an essential code for particular odors