Chemosensation 2

Question 1

List the 5 primary taste qualities and for each indicate whether sensory transduction involves ion channels or G-protein coupled receptors

Answer 1

1. Salty or Sour: ion channels (since are ionic stimuli).

2. Sweet, bitter, umami (glutamate): metabotropic receptors, G protein linked (more complex stimuli).

Question 2

All taste buds in the pharynx, extreme posterior tongue, esophagus, and epiglottis are innervated by

Answer 2

vagus nerve

Question 3

3 types of gustatory papillae

Answer 3

1. Fungiform papillae
2. Foliate papillae
3. Circumvallate papllae

Question 4

Fungiform papillae:

Answer 4

1. located in the anterior end of the tongue

2. innervated by the facial nerve.

Question 5

Foliate papillae:

Answer 5

1. on the side of the tongue

2. innervated by the facial nerve.

Question 6

Circumvallate papillae

Answer 6

1. located at the posterior end of the tongue

2. innervated by the glossopharyngeal nerve.

Question 7

Central taste pathway:

Answer 7

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).

Question 8

NST

Answer 8

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.

Question 9

Taste Lemnsicus:

Answer 9

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.

Question 10

Conscious appreciation of taste:

Answer 10

from pathway to insular cortex

Question 11

Orbitofrontal cortex:

Answer 11

where integration of taste and smell leads to perception of FLAVOR!!!

Question 12

Secondary gustatory cortex is located

Answer 12

in the orbitofrtonal surface

Question 13

Secondary gustatory cortex receives projections from

Answer 13

1. the primary gustatory area located on the interior insula

2. olfactory insula areas.

Question 14

Subconscious taste pathways:

Answer 14

NST also relays taste info to hypothalamus and amygdala for food intake regulation and visceral reactions to ingested foods.

Question 15

NST has reflex connections to

Answer 15

nuclei in the brainstem for

1. gagging (nuc ambiguous),
2. swallowing (nuc ambigusus, hypoglossal nuc.)
3. salivation (sup and inf salivatory nuc).

Question 16

Each odorant stimulates a number of receptors.

Answer 16

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!!!

Question 17

Primary principle of encoding odor quality = .

Answer 17

odor-specific map of glomeruli in olfactory bulb

Question 18

Axons of olfactory neurons cross the_____ and converge on ____.

Answer 18

ethmoid bone

glomeruli

Question 19

glomeruli

Answer 19

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.

Question 20

Olfactory receptor neurons expressing the same olfactory receptor protein project their axons _____

Answer 20

into the SAME glomerulus.

Question 21

Convergence of axons that stem from receptor neurons w/ same chemical specificity is basis for _____

Answer 21

ability of olfactory system to recognize structurally dissimilar odorants.

Question 22

Olfactory cortex: consists of:

Answer 22

lateral olfactory gyrus and part of the uncus

Question 23

Other major olfactory connections with limbic system:

Answer 23

1. amygdala
2. olfactory tubercle
3. entorhinal cortex.

Gives subconscious regulation of homeostasis, circadian, reproductive and other biological activity patterns.

Question 24

Amygdala + olfactory tubercle are interconnected with

Answer 24

hypothalamus

Question 25

Entorhinal cortex:

Answer 25

feeds into hippocampus, major player in storage and retrieval of MEMORIES!

Question 26

Olfactory cortex is divided into several areas including:

Answer 26

1. the piriform cortex 2. accessory olfactory nucleus 3. olfactory tubercle

Question 27

Piriform cortex projects to:

Answer 27

orbitofrontal cortex

Question 28

Orbitofrontal cortex:

Answer 28

association area for olfactory and taste information, gives us the conscious appreciation of smell!!!

Question 29

Output of olfactory bulb

Answer 29

1. projects directly to cortex, NOT through thalamus

Question 30

axons of output cells from the bulb collect into the

Answer 30

lateral olfactory tract

Question 31

Axons of the olfactory bulb project direction to

Answer 31

1. olfactory cortex | 2. portion of amygdala