3. Action potential

Question 1

what is threshold potential

Answer 1

-55 mV

Question 2

what is resting potential

Answer 2

-70 mV

Question 3

what does an excitatory stimulus cause

Answer 3

membrane potential depolarised- if above threshold potential= action potential generated

Question 4

what does an inhibitory stimulus cause

Answer 4

can reverse and hyper polarise the membrane- makes an action potential less likely

Question 5

define polarisation

Answer 5

the difference in charge across the neural membrane

Question 6

describe the activation and inactivation gates in na+ ion channels at rest

Answer 6

activation gate closed

inactivation gate open

Question 7

describe the activation and inactivation gates in k+ ion channels at rest

Answer 7

TRICK QUESTION
has no inactivation gate lol
one activation gate which opens and closes

Question 8

what happens when a stimulus reaches the neuron

Answer 8

ligand gated sodium channels open, diffuses into the neuron, resting potential becomes more positive

Question 9

what happens when critical threshold is reached

Answer 9

voltage gates activation gates in sodium channels open -> sodium floods into the neuron

=DEPOLARISATION

Question 10

when does the inactivation gate occur in the neuron

Answer 10

when the neuron becomes too highly positive

- the flow of sodium into the neuron stops

Question 11

at what point do k+ channels open

Answer 11

REPOLARISATION

when the intracellular environment is positive enough, K+ diffuses out of the cell

Question 12

why does hyper polarisation occur

Answer 12

voltage gated K+ channels close however this is a slow process, some K+ continues to move outside the cell, membrane potential becomes more negative than at rest

Question 13

what is the refractory period

Answer 13

when the neuron is in hyper polarisation it cannot fire another action potential

Question 14

at what point does the refractory period end

Answer 14

when the sodium potassium pump restores the resting membrane potential (-70 mV)

Question 15

at what part of the neuron are action potentials generated

Answer 15

the axon hillock

Question 16

what do the nodes of ranvier allow

Answer 16

allow sodium and potassium ion movement across the membrane

allow the action potential to ‘jump’ from one node to another

Question 17

what Is saltatory conduction

Answer 17

where the action potential jumps from one node to another

Question 18

what does the size of action potentials tell us

Answer 18

nothing- all action potentials are the same size, we can gather information based on the FREQUENCY

Question 19

what do electrical synapses use

Answer 19

gap junctions

Question 20

what do chemical synapses use

Answer 20

synaptic cleft

Question 21

which is the most common type of synapse:

electrical or chemical

Answer 21

chemical synapses

Question 22

what is the term that describes the amount of neurotransmitter in one vesicle

Answer 22

quantum

Question 23

describe the mechanism of synaptic transmission

Answer 23

1. depolarisation reaches synaptic terminal- ca2+ channels open
2. calcium influx causes vesicle fusion with pre-synaptic membrane
3. neurotransmitter released into the synaptic cleft
4. transmitter binds to post-synaptic receptor site

Question 24

what happens if an excitatory neurotransmitter binds to post-synaptic receptor site

Answer 24

sodium channels open triggering action potential

Question 25

what happens to the neurotransmitter following synaptic transmission

Answer 25

CATABOLISM
- degradation via protein enzymes in the post-synaptic neuron

UPTAKE
- of transmitter into axon terminal or glial cells

Question 26

what does EPSP & IPSP mean

Answer 26

EPSP- excitatory post-synaptic potential

IPSP- inhibitory post-synaptic potential

Question 27

what is summation

Answer 27

the process where a neuron integrates the EPSP and IPSPs

Question 28

name two neurotransmitters that can be both excitatory and inhibitory

Answer 28

acetylcholine

norepinephrine

Question 29

what happens when a neurotransmitter binds to an ionotropic receptor

Answer 29

binding= direct opening of ion channel

ions flow down their concentration gradient

Question 30

what happens when a neurotransmitter binds to a metabotropic receptor

Answer 30

binding causes indirect activation of G-protein

g-protein can activate a second messenger or cause a pore to open

Question 31

what is another name for a metabotropic receptor

Answer 31

GPCR - g-protein coupled receptor

Question 32

what is the structure of an inotropic receptor

Answer 32

4 or 5 subunits around a central pore in the membrane

Question 33

what is the structure of a metabotropic receptor

Answer 33

single protein with 7 membrane spanning region

Question 34

how are g-proteins activated

Answer 34

1. transmitter binds to receptor
2. GTP swaps for GDP on G protein
3. G-protein dissociates from receptor
4. 3 subunits of G-protein dissociate
5. alpha subunit activates ion channel
6. 3 subunits then attach to the receptor

Question 35

give an example of a second messenger

Answer 35

adenylate cyclase (cAMP)

Question 36

describe agonist drugs

Answer 36

drugs that mimic the actions of the neurotransmitter -

bind to receptor and activate

Question 37

describe antagonist drugs

Answer 37

drugs that block the action of the neurotransmitter

- binding to the receptor= no activation