82 - Special Senses III (Vision, Taste and Olfaction)

Question 1

What are the five primary taste sensations?

Answer 1

1 - Sour
2 - Salty
3 - Sweet
4 - Bitter
5 - Umami

Question 2

What can elicit the sour sensation?

Answer 2

intensity of sensation Depends on amount of hydrogen ion, caused by acids, e.g. HCl

Question 3

What can elicit the salty sensation?

Answer 3

Caused by ionized salts e.g. - NaCl

Question 4

What can elicit the sweet sensation?

Answer 4

Not caused by any one class of chemicals – e.g. some members of classes: sugars, glycols, alcohols, amino acids, inorganic salts of lead

Question 5

What can elicit the bitter sensation?

Answer 5

Not caused by any one class of chemicals - almost all though organic substances e.g. alkaloids - quinine, caffeine, strychnine, nicotine

Question 6

What can elicit the umami sensation?

Answer 6

This taste is elicited by monosodium glutamate, glutamate, and other amino acids. Taste common to protein rich foods like meat and cheese.

Question 7

Which cranial nerves are involved in taste innervation in the tongue and mouth?

Answer 7

CN VII (facial)
CN IX (glossopharyngeal)
CN X (vagus)

Question 8

Which cranial nerve innervates the anterior 2/3 of the tongue?

Answer 8

CN VII (facial) chorda tympani branch

Question 9

Which cranial nerve innervates the posterior 2/3 of the tongue?

Answer 9

CN IX (glossopharyngeal)

Question 10

Which cranial nerve innervates the soft palate?

Answer 10

CN VII (facial) greater superficial petrosal branch

Question 11

Which cranial nerve innervates the epiglottis and esophagus?

Answer 11

CN X (vagus)

Question 12

What are the receptor cells for taste?

Answer 12

Taste buds

Question 13

What is the typical life span of a taste cell?

Answer 13

10 days to 2 weeks

Question 14

What is the difference between a taste cell and a taste bud?

Answer 14

The taste bud is on the papillae and the taste cells is the only cells that is specialized for sensory transduction of taste sensation

Question 15

Are taste receptor cells neurons?

Answer 15

NO - they are not neurons, they release neurotransmitters onto different afferent (sensory) fibers which then carry that information to the brain

Question 16

How are olfactory receptor cells different from taste receptor cells?

Answer 16

They ARE neurons

Olfactory receptor cells are bipolar nerve cells that generate action potentials (via G protein and cell depolarization) in response to odorant molecule binding

Question 17

Further describe olfactory receptor cells

Answer 17

• Turnover rate is 60 days
• There are 400 odorant receptor proteins in humans
• Olfactory neurons expressing the same type of olfactory receptor project to the same glomeruli
• An odorant might interact with several different types of olfactory receptors.
• Different odorants cause different patterns of electrical activity in the olfactory bulb.

Question 18

Describe the interaction of an odorant and receptors

Answer 18

When an odorant molecule binds to receptor protein the associated G-protein is activated. This eventually (several steps you do not need to know) causes depolarization of the olfactory cell and the generation of an action potential.

Question 19

Can you generate new olfactory receptors?

Answer 19

Yes - New olfactory receptor neurons (ORN) are generated continuously from dividing stem cells which are maintained among the population of basal cells

Question 20

What are the probable biological roles of taste and olfaction?

Answer 20

• Edibility
• Diet selection
• Taste aversion (poisonous)

Question 21

What is bait-shyness?

Answer 21

If an animal feels sick after eating, assumption by the brain is that (most) novel food is responsible. Animal “loses its taste” for that food.

Question 22

Why is bait-shyness beneficial?

Answer 22

b. The ability to develop a taste aversion is considered an adaptive trait or survival mechanism that trains the body to avoid poisonous substances (e.g., poisonous berries) before they can cause harm.

Question 23

Describe the role of the limbic system in bait-shyness

Answer 23

Several routes for olfactory information to get to various parts of the limbic system

• Limbic pathways probably mediate affective component of odors - whether odor pleasant or unpleasant, etc.
• Bait-shyness or the clinical equivalent results from pairing taste and/or odor of a food with nausea and vomiting. This phenomenon is probably dependent on olfactory - limbic interconnections.

Question 24

Hyposmia

Answer 24

Impaired sense of smell

Question 25

Anosmia

Answer 25

Absence or loss of the sense of smell

• Specific anosmia – loss of specific smells
• General anosmia – complete loss of the sense of smell

Question 26

Parosmia

Answer 26

Disorder of the sense of smell, esp in the perception of odors that are not present

Question 27

Hypogeusia

Answer 27

Decreased taste sensation

Question 28

Ageusia

Answer 28

Absence of taste

Question 29

Parageusia

Answer 29

Perversion of the sense of taste/a bad taste in the mouth

• May be side effect of some drugs – makes things taste funny
• May also go along with psychological illness