Lecture 21

Question 1

What are chemoreceptors

Answer 1

sensory receptors that detect chemical changes in the body and external environment

Question 2

What constitutes the internal environment

Answer 2

peripheral chemoreceptors
central chemoreceptors

Question 3

Where are peripheral chemoreceptors and what do they do

Answer 3

in the aortic arch and carotid bodies
pressure sensitive nerve endings sense stretch in blood vessel walls
short-term blood pressure regulation

Question 4

Where are central chemoreceptors found and what do they do

Answer 4

Medulla oblongata.
- sense pH changes in CSF
- regulates breathing to alter CO2 in blood (alters pH)
- regulates heart rate and hence blood pressure to improve gas exchange

Question 5

What constitutes the external environment

Answer 5

gustatory receptors: tongue and palate detect dissolved molecules in saliva

olfactory receptors: nasal epithelium detects odorant molecules in air

Question 6

What are papillae

Answer 6

raised protrusions on tongue
contain taste buds
lives 10 days

Question 7

What are the three types of papillae

Answer 7

1. Circumvallate (back): bitter and sour
2. Foliate (middle): bitter
3. Fungiform (front): sweet and salty

Question 8

Describe a taste bud

Answer 8

contains all 5 sensing cells (sweet, bitter, salty, sour, umami) in every type of taste bud

receptor potential (not generator)

Question 9

Describe the tongue’s sensitivity

Answer 9

guides organisms toward nutritious foods and away from harmful or toxic ones

Question 10

How do taste buds contact saliva

Answer 10

taste buds extend microvilli through a taste pore to contact saliva

Question 11

what type of receptors are the different tastes for

Answer 11

salty and sour use ion channels
Sweet, umami, bitter use GPCRs

Question 12

which type of flavor has the highest receptor diversity

Answer 12

bitter

Question 13

What are the functions of the four categories of taste cells

Answer 13

Type I: astrocyte-like. primary support cells. salty (ionotropic)
Type II: GPCR; sweet, bitter, umami
Type III: sour
Type IV: basal cell, precursors to new taste receptor cells

Question 14

Which types of taste cells do not mediate a signal cascade

Answer 14

Type I and IV

Question 15

Describe the taste-transduction mechanism for salty tastes

Answer 15

Na+ channel allows sodium ions enter a taste bud cell, depolarizes the cell (ionotropic)

Question 16

Describe the taste-transduction mechanism for sour

Answer 16

caused by extracellular protons which release H+ through Otop-1 channel (gated, proton selective) .
entry of H+ inactivates a resting K+ channel.
depolarizes the cell

Question 17

Describe the taste-transduction mechanism of sweet, umami, and bitter

Answer 17

activate GPCRs (form heterodimer)
activate phospholipase C
cleaving PIP2 into IP3 and DAG
IP3 acts as a ligand binding to Ca2+ channel releasing Ca2+ from ER

Question 18

How is does Gustatory pathway transmit signals

Answer 18

signals from taste receptor are carried to gustatory cortex in the anterior insula and frontal lobe of the brain.

Question 19

What nerves relay gustatory signals

Answer 19

CN#7: Facial nerve
CN#9: Glossopharyngeal
CN#10: Vagus

Question 20

What is the the pathway of taste receptors to the brain

Answer 20

AP –> Brainstem –> Thalamus –> Gustatory cortex

Question 21

How are olfactory stimuli sensed

Answer 21

Olfactory epithelium Axons of the sensory cilia go through the cribriform plate of the ethmoid bone to end in glomeruli of olfactory bulb

Question 22

What cranial nerve is used to transmit olfactory signals

Answer 22

CN#1

Question 23

What type are olfactory receptor cells

Answer 23

small bipolar neurons

Question 24

what type of cells integrate olfactory information

Answer 24

Mitral cells : axons inside carry signal to the olfactory cortex located at the temporal lobe of the brain

granule cells: interneuron providing feedback inhibition to mitral cells

Question 25

Where does higher order processing occur

Answer 25

in Orbitofrontal cortex

Question 26

What is unique about olfactory cells in their transduction

Answer 26

olfactory signals don't pass through Thalamus

Question 27

Describe the vomeronasal organ

Answer 27

detects pheromones also called Jacobson's organ

Question 28

Where do axons of the vomeronasal neurons project to

Answer 28

the olfactory bulb

Question 29

Describe vomeronasal sensory neuron

Answer 29

coupled to different GPCR and also activates Phospholipase C therefore raises activity of IP3 and DAG raising Ca2+ level

Question 30

Describe insect antannea

Answer 30

olfactory organs detect chemicals in environment fundamental to animal reproduction and foraging behavior

Question 31

Olfactory neurons are replaced approximately every ___ days. while gustatory receptor cells are replaced every _______ days.

Answer 31

60 10-14

Question 32

The olfactory receptors which are ____________, are located in the _________ ____________ within the _______ _______.

Answer 32

chemoreceptors olfactory epithelium nasal cavity

Question 33

Flavor is a combination of _____ and _____

Answer 33

taste smell

Question 34

how are smell and flavor related

Answer 34

the sensation of flavor is significantly affected by the olfactory system smell contributes to overall perception of flavor

Question 35

What is the pathway for conscious taste perception

Answer 35

gustatory signal --> medulla oblongata --> thalamus --> Gustatory cortex in insula and frontal operculum

Question 36

How do olfactory signals travel to the brain

Answer 36

from the olfactory bulb (frontal) directly to the olfactory cortex (temporal lobe) and the limbic system (links smells with emotions) without going through the medulla oblongata