Sensory Systems part 2

Question 1

Most cells can sense chemical stimuli, what is this called?

Answer 1

Chemoreception

Question 2

Animals have many types of chemoreceptors, give examples of two

Answer 2

Olfaction and gustation

Question 3

What is olfaction?

Answer 3

Smell - the detection of chemicals in the air

Question 4

What is gustation?

Answer 4

Taste - detection of chemicals emitted from food

Question 5

What three structural criteria distinguish olfaction and gustation?

Answer 5

1. performed by different sense organs
2. different signal transduction mechanisms
3. processed in different integrating centres

Question 6

What type of receptors does the olfactory system contain?

Answer 6

Odorant receptors

Question 7

Binding of an odorant to an odorant receptor causes what?

Answer 7

A conformational change

Question 8

What happens once a odorant binds to an odorant receptor causing a conformational change?

Answer 8

A G protein is activated, G-olf. It then moves through the membrane and activates the enzyme adenylate cyclase

Question 9

What does the enzyme adenyl cyclase convert into what?

Answer 9

It converts ATP into cAMP

Question 10

What is the purpose of cAMP in the olfactory system response?

Answer 10

cAMP opens cAMP gated ion channels

Question 11

Once cAMP gated channels are opened, what two ions can enter the cell causing a generator potential?

Answer 11

Ca2+ and Na+

Question 12

How do Cl- ions leave the cell and cause depolarisation?

Answer 12

The Ca2+ ions that enter the cell opens ca2+ activated cl- channels, causing cl- to leave the cell, increasing the depolarisation

Question 13

How are action potentials finally triggered by the olfactory system?

Answer 13

The generator potential opens the voltage gated na+ channels, triggering action potentials

Question 14

The gustatory system consists of five classes of tastants, what are these?

Answer 14

Salty, sweet, bitter, sour and umami

Question 15

What do sweet, umami and salty tastes indicate?

Answer 15

Carbohydrates, proteins and ions

Question 16

What do bitter and sour tastes indicate?

Answer 16

Potentially toxic substances

Question 17

*Label this vertebrate taste bud

Answer 17

There

Question 18

Taste receptor transduction pathways vary for

Answer 18

The different tastes, salty, sour, sweet, bitter

Question 19

In the salty taste receptor transduction pathway what happens?

Answer 19

The Na+ from salty food enters through a Na+ channel
The resulting depolarisation opens voltage gated Ca2+ channels
The influx of Ca2+ causes neurotransmitter release

Question 20

What happens in the sour taste receptor pathway?

Answer 20

H+ ions from sour foods block the K+ channel
This blockage prevents K+ from leaving the cell
The resulting depolarisation opens voltage gated ca2+ channels
The influx of Ca2+ causes neurotransmitter release

Question 21

What happens in the sweet taste receptor transduction pathway?

Answer 21

A sweet substance binds to its receptor causing a conformational change
The activated G protein, gustducin activates adenylate cyclase
Adenylate cyclase catalyses the conversion of ATP to cAMP
The cAMP activates a protein kinase that phosphorylates and closes a K+ channel
The resulting depolarisation opens voltage gated ca2+ channels
The influx of Ca2+ causes neurotransmitter release

Question 22

What happens in the bitter taste receptor transduction pathway?

Answer 22

A bitter substance binds to its receptor, causing a conformational change
The activated g protein, transducin activates phospholipase c
PLC catalyses the conversion of PIP2 into the second messenger IP3
IP3 causes the release of Ca2+ from intracellular stores
The influx of Ca2+ causes neurotransmitter release