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psychobiology > communication within and between neurones (2) > Flashcards

communication within and between neurones (2) Flashcards

1
Q

how long can axons be

A

a few cm

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2
Q

signals need to travel from - to end of -

A

cell body, axon

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3
Q

why is communication not via diffusion of chemicals

A

we can respond to stimuli very quickly especially in reflexes- communication is fast,
diffusion of chemicals would be far too slow

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4
Q

what type of signal occurs in neurones

A

electrical

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5
Q

what type of state is the resting membrane potential

A

an unstable state

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6
Q

what happens while a neurone is in it’s passive state

A

energy is expended to maintain the unstable state of the resting membrane potential

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7
Q

what happens upon a trigger to a neurone

A

because the neurone is in an unstable state, stored energy is then released

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8
Q

what is the release of energy upon trigger of a neurone called

A

an action potential

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9
Q

what is the membrane of a neurone

A

a phospholipid bilayer

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10
Q

what type of ion does the lipid bilayer prevent passing through?

A

charged molecules/ ions

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11
Q

how does the lipid bilayer create an unstable resting membrane potential

A

membrane creates barrier between inside and outside of neurone, creating a disparity between composition of liquid inside compared to inside

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12
Q

what is embedded within the barrier

A

proteins with various roles

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13
Q

what does the sodium/potassium exchange transporter do

A

moves sodium ions outside of the neurone and moves potassium ions into the neurone

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14
Q

do the exchange transporters move more sodium out or more potassium ions in?

A

more sodium ions out

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15
Q

sodium and potassium are both cations, meaning…

A

they each carry a single positive charge

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16
Q

because transporter moves more sodium ions out of the cell than it does potassium ions into the cell, the charge is…

A

more negative inside the cell, as there is an accumulation of positively charged ions outside of the cell

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17
Q

chloride is an…

A

anion, holds negative charge

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18
Q

what is the difference in charges between the inside and outside of a neurone cell?

A

-70mV (minus as the charge inside of the cell is more negative)

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19
Q

what is caused by the difference in charges between the inside and outside of a neurone cell

A

electrostatic pressure

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20
Q

what is electrostatic pressure

A

the idea that positively charged ions want to move to an area of negative charge

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21
Q

what does a transporter do

A

moves specific ions using energy

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22
Q

what forces push sodium back into the cell

A

electrostatic pressure AND diffusion

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23
Q

why does sodium not move back into the cell despite electrostatic pressure and diffusion

A

it can’t move through the phospholipid bilayer

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24
Q

why does a little sodium get back into the cell and what happens to it then

A

because the lipid membrane is leaky, transporters push them back in

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25
Q

what forces act to push K out of the cell

A

diffusion

26
Q

what forces act to keep K in the cell

A

electrostatic pressure

27
Q

why does K stay in the cell

A

the forces of diffusion balance out the force of electrostatic pressure

28
Q

describe the neurone cell at resting state

A

more sodium outside and more potassium inside, charge more positive outside cell and more negative inside cell, cell has electrical excitability (electrically charged ions would move if we let them), energy is being used by the sodium/ potassium transporter

29
Q

what happens in stage 1 of an action potential

A

the membrane depolarises

30
Q

why is the membrane said to be polarised when at rest

A

because there is differential charge inside and outside the cell

31
Q

what does depolarisation refer to

A

anything that brings the membrane closer to a charge of 0

32
Q

at what point to voltage-gated sodium channels open

A

-55mV

33
Q

what happens when voltage-gated sodium channels open

A

the membrane is much more permeable to sodium, and sodium moves into the cell via diffusion and because of electrostatic pressure

34
Q

what happens as sodium moves into the cell

A

the cell becomes less negatively charged

35
Q

what happens when the cell becomes positively charged

A

electrostatic pressure works against sodium moving into the cell, however diffusion overcomes this pressure

36
Q

what 2 channels open in stage 1 of an action potential

A

sodium and potassium

37
Q

what happens in stage 2 of an action potential

A

the membrane potential gets more positive as cations flood in

38
Q

what ion leaves the cell in stage 2 of an action potential

A

potassium, as the channels are open and there is no electrostatic pressure opposing them

39
Q

when do voltage-gated sodium channels close again

A

+40mV

40
Q

what happens in action potential stage 3

A

membrane repolarisation

41
Q

why does the membrane depolarise in stage 3

A

sodium ions and potassium leave the cell, so the cell starts becoming negatively charged again

42
Q

what happens in stage 4

A

membrane hyperpolarisation

43
Q

what is hyperpolarisation and why does it occur in stage 4

A

it is where the cell membrane becomes extremely negatively charged, it occurs becomes positively charged potassium cations continue to leave the cell

44
Q

what happens in stage 5

A

potassium channels close and other processes return the balance to resting membrane potential

45
Q

after an action potential is generated, what happens

A

the action potential is regenerated further down the membrane

46
Q

what makes up the myelin sheath

A

oligodendrocytes

47
Q

what do glia do

A

wrap around the neurone forming an insulating layer where an action potential can’t form, forming nodes

48
Q

what do nodes do

A

force action potentials to jump between nodes

49
Q

what happens to the action potential as it travels underneath the myelin sheath

A

it decreases, and then is regenerated at the nodes to save energy

50
Q

are action potentials always the same size

A

yes

51
Q

what is a chemical synapse

A

a physical gap between the neurones which is around 20nm

52
Q

what is in the terminal of presynaptic neurones

A

vesicles containing chemicals called neurotransmitters

53
Q

what are the 2 types of post synaptic potentials

A

excitatory and inhibitory

54
Q

what happens in an EPSP

A

they make it more likely that an action potential will fire because it brings the membrane potential closer to the threshold

55
Q

what causes an EPSP

A

Generally happens if we are opening cation channels (positive ion)

56
Q

what causes IPSP

A

open anion (negatively charged ion) channels

57
Q

what happens in an IPSP

A

As the membrane becomes less negative it creates less electrostatic pressure, so more chloride will move in- overall makes an action potential less likely to occur

58
Q

what are the 2 types of synapses

A

chemical and electrical (also called gap junctions)

59
Q

describe an electrical synapse

A

2 neurones are fused together by a single channel so that ions can move directly from 1 neurone to another

60
Q

when can an electrical charge move in both directions

A

in an electrical synapse

psychobiology (3 decks)

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