Integrated Function of Nervous System

Question 1

proboscis extension response (2)

Answer 1

• if flies touch sweet food with their taste bud feet, they extend their proboscis
• if flies touch yucky food with their taste bud feet, they don’t extend their proboscis

Question 2

how do we “sense” our environment (3)

Answer 2

• sensory neurons related to our “five” senses
• specific neuron is specific to a certain stimuli (eye neurons can’t sense smell)
• to sense something, a neuron must depolarize in response to that something

Question 3

how would a sensory neuron responsible for detecting smell cause depolarization

Answer 3

• express a receptor that opens Na+ channels in response to a particular odourant

Question 4

smell sensing signalling pathway (2)

Answer 4

1. odourant binds to receptor and many steps occur to get a graded potential
2. each step can have amplification occur so that one odourant molecule can cause a large cell response

Question 5

what determines the diversity of senses

Answer 5

• the diversity of receptors to different types of molecules associated with that sense

Question 6

how do taste neurons detect “sweet” taste (3)

Answer 6

• a G-protein is activated that, through many steps, causes Na” channels to open
• Na+ influx will depolarize cells and trigger action potentials
• axons of taste neurons will synapse in the brain to detect the taste (sweet vs bitter)

Question 7

what would happen if a capsaicin receptor was expressed in sweet neurons (2)

Answer 7

• fly would eat capsaicin

- all brain knows is that the sweet neuron is activated, even if the spicy receptor is what triggered it

Question 8

when will flies extend their proboscis

Answer 8

• when any compound+receptor leads to depolarization in SWEET neurons

Question 9

when will flies not extend their proboscis after tasting foods

Answer 9

• when any compound + receptor leads to depolarization in BITTER neurons

Question 10

what would happen if we express a blue-light gated Na+ channel in sweet neurons and then flashed blue light on the flies (3)

Answer 10

1. Na+ would enter sweet taste neurons
2. sweet taste neurons would depolarize, causing action potentials if they reach threshold
3. flies will extend their proboscis

Question 11

optogenetics (2)

Answer 11

• biological technique to control the activity of neurons or other cell types with light
• uses light-gated ion channels

Question 12

basic steps to optogenetics (2)

Answer 12

1. genetically engineer the organism to express a light receptor in the relevant cells
2. expose those cells to light

Question 13

sensilla of drosophila (3)

Answer 13

• contain multiple sensory neurons
• sensitive to different tastants
• information is integrated via interneurons

Question 14

interneuron function

Answer 14

• receive input from multiple neurons and send out ‘summary’ of this info to the next neuron