Chemical Senses - Olfaction / Taste

Front 1

Why when presented with a mixture of red and green do we see yellow?

Back 1

Because red causes LATERAL INHIBITION of green, and green causes LATERAL INHIBITION of red and so we see yellow.

Front 2

Do we have yellow photoreceptors?

Back 2

No; only blue/green/red

Front 3

where are our olfactory receptors located?

Back 3

In olfactory epithelium (mucosa)

Front 4

how many olfactory receptors in humans?

Back 4

10 million

Front 5

What are olfactory receptors?

Back 5

Bipolar brain cells - neurons - unique because they are the only part of the brain that actually comes in contact w/ the outside world.

Front 6

What are olfactory receptors related to?

Back 6

Highly differentiated epithelial cells.

Front 7

What makes up the receptor component of bipolar epithelial olfactory neurons?

Back 7

An apical dendrite extending to the epithelial surface, expanded into a knob.

Front 8

Where are the actual receptor molecules for olfactory neurons?

Back 8

In cilia extending up out of the knob.

Front 9

How are bipolar olfactory receptor neurons connected to the brain?

Back 9

By a basal axon extending thru the cribiform plate to synapse with the olfactory bulb.

Front 10

What are the receptor molecules in olfactory cilia?

Back 10

a large gene family of oderant receptor molecules - 1 type is expressed per neuron.

Front 11

What type of receptors are the oderant receptors?

Back 11

7 transmembrane Gprotein coupled

Front 12

4 different celltypes contained in the olfactory mucosa/epithelium:

Back 12

1. Receptor cells (bipolars)
2. Free nerve endings
3. Support cells
4. Basal cells

Front 13

What do the free nerve endings do?

Back 13

Detect sensations like tingling of menthol/ozone in mountain air

Front 14

What do support cells do?

Back 14

Secrete mucus

Front 15

What do basal cells do?

Back 15

Cell turnover

Front 16

Lifespan of olfactory neurons:

Back 16

1-2 months

Front 17

What happens if you have a severe blow to the head?

Back 17

It can shear off all olfactory receptors, but b/c you have basal cells you can regain sense of smell within 1-2 months.

Front 18

Axons of the olfactory bipolar cells project to:

Back 18

The olfactory bulb

Front 19

What 4 cells are in the olfactory bulb? Functions?

Back 19

1. Periglomerial (local lateral inhibition)
2. Granule (local lat inhib)
3. Tufted cells - output
4. Mitral cells - output

Front 20

How do the olfactory axons of bipolar cells get to the olfactory bulb?

Back 20

By penetrating the cribiform plate

Front 21

First layer of cells in the olf bulb (after penetrating crib pt)

Back 21

Periglomerular cells

Front 22

What cells are just interior to the periglomerular cells?

Back 22

Tufted and Mitral

Front 23

What lies below the mitral layer?

Back 23

Granule cells in the granule layer

Front 24

What are Tufted and Mitral cells?

Back 24

Output cells form bulb to olfactory tract.

Front 25

What is the function of mitral cells?

Back 25

MAJOR OUTPUT of olfactory bulb into the olfactory tract
-Recieve signal from incoming olfactory nerve fibers - synpse at glomeruli

Front 26

How many areas of the brain receive olfactory messages? What are they?

Back 26

Five:
-Anterior olfactory nucleus
-Olf tubercle (ant perf subst)
-Pyriform cortex
-Amygdaloid complex
-Enterorhinal Cortex

Front 27

How are smells localized?

Back 27

By communication of the two olfactory bulbs via their projections to the cortex

Front 28

What 2 major components of smell make this sensation distinct?

Back 28

-Emotion
-Memory

Front 29

Function of the anterior olfactory nucleus:

Back 29

Communication between the two bulbs - allows LOCALIZATION of particular smells by comparison

Front 30

Where is the anterior olfactory nucleus?

Back 30

In the anterior commissure

Front 31

Function of the olfactory tubercle:

Back 31

Conscious perception of smell

Front 32

Another name for olfactory tubercle:

Back 32

Anterior perforated substance

Front 33

Where is the olfactory tubercle located? What does it project to?

Back 33

-Located behind olf tract
-Projects to Medial dorsal nucleus of thalamus
-Then to orbital frontal cortex

Front 34

What does the pyriform cortex consist of?

Back 34

Anterior uncus
Anterior parahippocampal gyrus

Front 35

Function of pyriform cortex:

Back 35

Olfactory discrimination

Front 36

Function of amygdaloid complex:

Back 36

-Emotional component of smell
-Autonomic activity
-Endocrine activity

Front 37

Where is the entorhinal cortex?

Back 37

The parahippocampal gyrus

Front 38

What is the main olfactory cortex?
What is secondary?

Back 38

Main: Pyriform (uncus/ant PHC)
2ndry: Entorhinal

Front 39

Where does the entorhinal cortex project to?

Back 39

The hippocampus

Front 40

Function of hippocampus in olfaction:

Back 40

Memory function

Front 41

Function of pyriform cortex:

Back 41

smell discrimination

Front 42

Function of hippocampus:

Back 42

Memory of smells

Front 43

Function of orbital frontal cortex and the thalamic component of olfaction:

Back 43

Conscious awareness of smells

Front 44

What is the nature of all molecules that you can smell?

Back 44

They must be fat soluble to penetrate the submucosa and bind trnasmembrane gprotein receptors.

Front 45

What determines which oderant receptor will be bound by a stimulant?

Back 45

-Shape
-Size
-Chemical properties of the oderant stimulus

Front 46

What encodes stimulus quality of olfaction?

Back 46

Labeled line codes - specific for individual smells.

Front 47

How does smell sensation differ from vision?

Back 47

There isn't cancelling out of smells - smell cookies and pizza baking both.

Front 48

Where are taste buds located?

Back 48

-Tongue
-Palate
-Pharynx
-Epiglottis
-Upper 1/3 of esophagus

Front 49

4 Cell types in the taste bud:

Back 49

-Support (glial)
-Receptor cells
-Basal (regenerative)
-Afferent fiber

Front 50

What is the major difference of taste receptors compared to smell?

Back 50

Taste receptors have no apical dendrite to take info to a bipolar cell; rather they need an afferent fiber

Front 51

Where does the afferent fiber for taste sensation go?

Back 51

to the CNS

Front 52

5 types of taste sensation

Back 52

-Bitter
-Salty
-Sour
-Sweet
-Umami (msg)

Front 53

Nerve for Taste from anterior tongue:

Back 53

Facial VII - chorda tympani

Front 54

Nerve for Taste from posterior tongue:

Back 54

Glossopharyngeal - IX - via lingual branch

Front 55

Nerve for Taste from epiglottis / upper 1/3 esophagus:

Back 55

Vagus - X - laryngeal branch

Front 56

Where do the nerve fibers carrying taste sensation from the buds go?

Back 56

Solitary nucleus of medulla

Front 57

Where does the STN of medulla project?

Back 57

VPM nucleus of the Thalamus

Front 58

Where does taste input travel from the thalamus VPM?

Back 58

Two places:
1. Gustatory region of Postcentral gyrus
2. Insula

Front 59

Function of the insula:

Back 59

Conscious taste perception - you become very concious of it as you carefully pry open the insula and WHAM out pops the tongue sticking out at you.

Front 60

What is the specific Gprotein for taste?

Back 60

Gustducin

Front 61

3 features of taste encoding:

Back 61

-Broadly tuned receptors
-Labeled lines
-Taste modification / adaptation

Front 62

What is taste adaptation?

Back 62

The change in sourness of lemonade as sugar is added

Front 63

What is taste modification?

Back 63

Brushing your teeth right after eating orange juice - makes the OJ seem more sour.

Front 64

What is sour?

Back 64

Acid - HCl

Front 65

What is Salt?

Back 65

NaCl

Front 66

What is bitter?

Back 66

Quinine

Front 67

How do we get taste adaptation and modification?

Back 67

By lateral inhibition.