Chemosensation

Question 1

Ageusia

Answer 1

loss of taste

Question 2

Anosmia

Answer 2

loss of smell

Question 3

Chemosensory systems

Answer 3

taste, smell, chemesthesis

Question 4

Description of basic taste receptors

Answer 4

sour= ion channel
salty= ion channel
sweet=  GPCR
bitter= GPCR
Umami= GPCR

Question 5

How is taste information transmitted?

Answer 5

Taste information is carried on facial and glossopharyngeal nerves to end in the nuc. solitary tr. From there they can project to VPM in thalamus which then project to the gustatory cortex.

Question 6

What nerve carries taste from ant 2/3 of tongue?

Answer 6

Facial

Question 7

What nerve carries taste from post 1/3 of tongue?

Answer 7

Glossopharyngeal

Question 8

Types of taste buds

Answer 8

Circumvallate= large, in back
Foliate= side
Fungiform= in front

Question 9

How do the GPCR work in taste?

Answer 9

2nd messenger cascade

Involves PLC, IP3R, the Trp channel which when activated releases ATP

Question 10

Olfactory excitation

Answer 10

Odorant binds to the receptor protein, G-protein (Golf) activates adenylate cyclase which locally generates cAMP.

cAMP opens a nearby cAMP-gated ion channel which permits influx of Na+ and Ca2+. The local increase in Ca2+ opens adjacent Ca2+-gated Chloride channels.

Since Cl- levels in the receptor cell are quite high, opening a Cl- channel results in outflow of Cl- thereby further depolarizing the cell.

This amplified depolarization is sufficient to drive the cell to threshold thereby triggering an action potential.

Question 11

Smell (receptor cell, cranial nerve(s), primary sensory nucleus in CNS)

Answer 11

Receptor cell: ciliated, bipolar neuron
Cranial Nerve: CN I
Primary sensory nucleus: Olfactory bulb

Question 12

Taste (receptor cell, cranial nerve(s), primary sensory nucleus in CNS)

Answer 12

Receptor cell: modified epithelial cell
Cranial Nerve: CN VII, IX, X
Primary sensory nucleus: Nucleus of sol tract

Question 13

Chemesthesis (receptor cell, cranial nerve(s), primary sensory nucleus in CNS)

Answer 13

Receptor cell: Free nerve ending of cranial ganglion cell
Cranial Nerve: CN V
Primary sensory nucleus: Spinal trigeminal nucleus

Question 14

How does transmission of olfactory info occur?

Answer 14

Axons of the olfactory neurons converge on glomeruli (tangles of axons and dendrites) present at the outer layer of the olfactory bulb.

Olfactory receptor neurons expressing the same olfactory receptor protein project their axons to the same glomerulus.

The primary principle of encoding odor quality is through a odor-related map of glomeruli in the olfactory bulb. In contrast, within the olfactory epithelium, receptor cells expressing a common receptor are scattered throughout the epithelium.

The response to single odorants is usually not localized to a single glomerulus but is distributed in wide areas of the glomerular layer. Therefore, identification of an odor entails recognition of the pattern of activity across all glomeruli of the olfactory bulb.

Info then goes from olfactory bulb to the Primary Olfactory Cortex
(Piriform Cortex)

Question 15

Trp channels

Answer 15

warm/hot capsaicin receptors