Nerves 3

Question 1

How much does the resting membrane potential have to be depolarised to to fire an action potential?

Answer 1

about -55mV

Question 2

What is a generator potential?

Answer 2

a graded potential occurring at sensory nerves e.g pressure on skin

Question 3

What is an excitatory postsynaptic potential?

Answer 3

a potential that will cause the cell to fire

Question 4

What is an inhibitory postsynaptic potential?

Answer 4

a potential that will inhibit the cell from firing

Question 5

What is the graded potential that occurs in the muscle after stimulation by a motor neurone called?

Answer 5

endplate potential

Question 6

What is the function of graded potentials?

Answer 6

to determine when an action potential is fired

Question 7

What are 4 examples of graded potentials?

Answer 7

generator potentials - at sensory receptors
postsynaptic potentials- at synapses
endplate potentials - at neuromuscular junction
pacemaker potentials - in pacemaker tissues

Question 8

What are 4 key properties of graded potentials?

Answer 8

• decremental
• are graded
• can be depolarising or hyper polarising
• can summate

Question 9

Why are graded potentials decremental?

Answer 9

current leaks out

Question 10

What is meant by the fact that graded potentials are ‘graded’?

Answer 10

signal stimulus intensity in their amplitude

Question 11

How can a graded potential cause an inhibitory postsynaptic potential?

Answer 11

by opening Cl- channels (this makes the cell more negative, preventing an AP from being generated)

Question 12

How are fast IPSPs generated?

Answer 12

by opening chlorine channels

Question 13

How are slow IPSPs generated?

Answer 13

by opening potassium channels to allow the potassium to leave

Question 14

What are the names of two neurotransmitters that will cause an IPSP?

Answer 14

GABA and Glycine

Question 15

How do transmitters depolarise cells?

Answer 15

open type of channels permeable to potassium and sodium - more sodium gets in than potassium gets out therefore causing the cell to depolarise

Question 16

How are fast EPSPs generated?

Answer 16

by opening sodium/ potassium channels

Question 17

How are slow EPSPs generated?

Answer 17

blocking leaky potassium channels

Question 18

What are postsynaptic potentials produced by?

Answer 18

a neurotransmitter opening or closing ion channels - ligand gated ion channels

Question 19

What is meant by the fact that graded potentials can summate?

Answer 19

they can add to each other

Question 20

What is temporal summation?

Answer 20

when input from the same stimulus adds to each other

Question 21

What is spatial summation?

Answer 21

when two different stimuli generate EPSPs and they add to each other

Question 22

What is synaptic integration?

Answer 22

taking all the inputs and deciding whether to fire an action potential

Question 23

Why would EPSPs received nearer the axon hillock have greater influence on whether an action potential is fired?

Answer 23

graded potentials are decremental and so the nearer the graded potential is to the axon hillock where the AP is going to be generated then the more graded potential that is going to reach the axon hillock and therefore the larger the response than if it were further apart