T17. SPECIAL SENSES I

Question 1

What do interceptors detect in the context of chemical senses?

Answer 1

Chemical changes within the body.

Question 2

What do exteroceptors include in chemical senses?

Answer 2

Taste and smell.

Question 3

What does taste respond to?

Answer 3

Chemicals dissolved in food and drink.

Question 4

What does smell respond to?

Answer 4

Chemical molecules in the air.

Question 5

What is gustation?

Answer 5

The sensation that results from the action of chemicals on taste receptors (buds).

Question 6

Where are taste buds mainly located?

Answer 6

Approximately 4000 mainly on the tongue, but also inside cheeks, soft palate, pharynx, and epiglottis.

Question 7

What are papillae?

Answer 7

Bumps on the tongue where taste buds are located.

Question 8

Do filiform papillae have taste buds?

Answer 8

No, they do not have taste buds and are important for food texture.

Question 9

What type of papillae have a moderate number of taste buds?

Answer 9

Foliate papillae.

Question 10

Where are taste buds located in fungiform papillae?

Answer 10

At the tips and sides of the tongue.

Question 11

Where are vallate (circumvallate) papillae located and how many taste buds do they contain?

Answer 11

Located at the rear of the tongue; contain 1/2 of all taste buds.

Question 12

What is the structure of a taste bud?

Answer 12

Lemon-shaped group of 40–60 taste cells, supporting cells, and basal cells.

Question 13

What are taste cells?

Answer 13

Specialized epithelial cells with apical microvilli (taste hairs) that contact chemicals and act as receptor surfaces.

Question 14

How do taste cells behave?

Answer 14

Like neurons by depolarizing and producing action potentials; they release neurotransmitters onto sensory neurons at their base.

Question 15

What are basal cells in taste buds?

Answer 15

Stem cells that replace taste cells every 7 to 10 days.

Question 16

What are supporting cells in taste buds?

Answer 16

Cells that resemble taste cells but do not have taste hairs, synaptic vesicles, or a sensory role.

Question 17

How many taste cell types are in each taste bud?

Answer 17

Each taste bud has cells sensitive to each category of tastes.

Question 18

What must happen for molecules to be tasted?

Answer 18

Molecules must dissolve in saliva and flood the taste pore.

Question 19

What are the five primary taste sensations?

Answer 19

Salty, sweet, sour, bitter, umami.

Question 20

What produces salty taste?

Answer 20

Sodium or potassium ions.

Question 21

What is sweet taste associated with?

Answer 21

Carbohydrates.

Question 22

What produces sour taste?

Answer 22

Acids such as those in citrus fruits.

Question 23

What produces bitter taste?

Answer 23

Spoiled foods and alkaloids like nicotine, caffeine, quinine, and morphine.

Question 24

What causes umami taste?

Answer 24

Amino acids in chicken or beef broth.

Question 25

What does hot pepper stimulate?

Answer 25

Free nerve endings (pain), not taste buds.

Question 26

What are the two mechanisms of taste action?

Answer 26

Activation of second messenger systems and direct depolarization of cells.

Question 27

How does the second messenger system for taste work?

Answer 27

Sugars, alkaloids, and glutamate bind to receptors, activate G-proteins (gustducin), leading to downstream effects like K⁺ channel closure or Ca²⁺ release.

Question 28

What taste molecules use the second messenger system?

Answer 28

Sugars, alkaloids (e.g., quinine), and glutamate (umami).

Question 29

What happens in direct depolarization of taste cells?

Answer 29

Sodium and acids penetrate cells and directly depolarize them.

Question 30

What is the result of either taste mechanism?

Answer 30

Release of neurotransmitters that stimulate dendrites at the base of taste cells.

Question 31

How does salty taste work?

Answer 31

Na⁺ enters the taste cell and depolarizes it.

Question 32

How does sour taste work?

Answer 32

H⁺ ions enter the cell and depolarize it.

Question 33

How does sweet and umami taste work?

Answer 33

Sugar or glutamate binds to receptor, activates G-proteins and second messengers, which close K⁺ channels.

Question 34

How does bitter taste work?

Answer 34

Quinine binds to a receptor, activates G-protein and second messenger system to release Ca²⁺ into the cell.

Question 35

What nerve collects taste info from anterior two-thirds of the tongue?

Answer 35

Facial nerve (cranial nerve VII).

Question 36

What nerve collects taste info from posterior one-third of the tongue?

Answer 36

Glossopharyngeal nerve (cranial nerve IX).

Question 37

What nerve collects taste info from palate, pharynx, and epiglottis?

Answer 37

Vagus nerve (cranial nerve X).

Question 38

Where do all taste fibers go first in the brainstem?

Answer 38

Solitary nucleus in the medulla oblongata.

Question 39

What are the two destinations of taste signals from the solitary nucleus?

Answer 39

Hypothalamus and amygdala (for autonomic reflexes); and thalamus (for conscious taste perception).

Question 40

What autonomic reflexes are controlled by the hypothalamus and amygdala from taste signals?

Answer 40

Salivation, gagging, and vomiting.

Question 41

Where does the thalamus send taste information?

Answer 41

To the gustatory cortex for conscious sense of taste.

Question 42

What is olfaction?

Answer 42

The sense of smell.

Question 43

How many odors can the olfactory mucosa distinguish?

Answer 43

Approximately 2000 to 4000 odors.

Question 44

What cells are found in the olfactory mucosa?

Answer 44

Olfactory cells, epithelial supporting cells, and basal stem cells.

Question 45

What is unique about the exposure of olfactory neurons?

Answer 45

They are the only neurons in the body directly exposed to the external environment.

Question 46

What is the lifespan of olfactory neurons?

Answer 46

60 days.

Question 47

What type of neurons are olfactory cells?

Answer 47

Bipolar neurons with ciliated dendrites (olfactory hairs) that project into the nasal cavity.

Question 48

What do olfactory hairs do?

Answer 48

They have binding sites for odorant molecules.

Question 49

Where do olfactory axons collect?

Answer 49

Into small fascicles that pass through the cribriform foramina of the ethmoid bone.

Question 50

What cranial nerve do the olfactory fascicles make up?

Answer 50

Cranial Nerve I (olfactory nerve).

Question 51

What do basal cells in olfactory epithelium do?

Answer 51

Divide and differentiate into new olfactory cells.

Question 52

What are olfactory receptors?

Answer 52

G-protein-coupled receptors that activate adenylate cyclase when odor binds.

Question 53

What happens when odor binds to olfactory receptor?

Answer 53

Adenylate cyclase is activated, forming cAMP which opens Na⁺ and Ca²⁺ channels.

Question 54

Where do olfactory cells synapse first?

Answer 54

In the olfactory bulb on dendrites of mitral and tufted cells.

Question 55

What are glomeruli in the olfactory bulb?

Answer 55

Spherical clusters where fibers from olfactory cells with the same receptor type converge.

Question 56

What forms the olfactory tracts?

Answer 56

Axons of tufted and mitral cells.

Question 57

Where do olfactory tracts lead?

Answer 57

Primary olfactory cortex and secondary destinations like hippocampus, amygdala, and hypothalamus.

Question 58

What functions are served by secondary olfactory destinations?

Answer 58

Odor identification, integration with taste, emotional and memory responses, and visceral reactions.