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Cells to Organisms - Practicals > Practical 2. Simulation of Resting Membrane Potential and Action Potential using Metaneuron > Flashcards

Practical 2. Simulation of Resting Membrane Potential and Action Potential using Metaneuron Flashcards

1
Q

What is neurotransmission ?

A

The conversion of an electrical signal which passes down a neuron, into a chemical messenger that passes this signal to the next neuron

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2
Q

What are synapses filled with ?

A

Neurotransmitters

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3
Q

What is the release of neurotransmitters triggered by ?

A

The activation of the presynaptic cell

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4
Q

What does the action of the neurotransmitter at the post synaptic site lead to ?

A

Either an activation or an inhibition of the post synaptic neuron

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5
Q

What is on either side of the neuronal membrane ?

A

Positive and negative ions

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6
Q

What is the resting membrane potential determined by ?

A

The distribution of positively and negatively charged ions on either side of the neuronal membrane

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7
Q

What is the resting membrane potential with respect to the extracellular medium ?

A

-65 mV

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8
Q

Where does the local net positive charge on the outside of the neuronal cell membrane and a local negative charge on the inside occurr ?

A

Really close to the membrane

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9
Q

How is a net positive charge outside the cell maintained with respect to the inside ?

A

Positive ions have to be pumped out of the cell

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10
Q

How are positive ions pumped into the cell ?

A

Sodium/potassium ATPase

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11
Q

What is the function of the sodium/potassium ATPase ?

A

Exports three sodium ions out for every 2 potassium ions it pumps into the cell

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12
Q

What does the pumping of the sodium/potassium ATPase do ?

A

Leaves a net negative charge on the inside of the cell

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13
Q

How does the neuron maintain high intracellular potassium and high extracellular sodium ?

A

Sodium/potassium ATPase

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14
Q

What does the sodium/potassium ATPase pump consume ?

A

ATP

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15
Q

What is the cells principle energy source ?

A

ATP

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16
Q

How much of the neurons energy budget does the sodium/potassium ATPase use up ?

A

2/3

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17
Q

What is energy used for ?

A

To maintain the polarised state

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18
Q

What must happen for the neuron to fire ?

A

The membrane potential has to become less negative ie. depolarise

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19
Q

What can depolarise the membrane potential ?

A

Stimulation of the neuron

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20
Q

What is the most important type of stimulation ?

A

The arrival of the action potentials

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21
Q

What is depolarisation typically initiated by ?

A

The sodium influx

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22
Q

How is sodium influxed ?

A

Through a ligand gated sodium channel

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23
Q

What opens or gates the sodium channel ?

A

Neurotransmitter binding

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24
Q

What is the ligand ?

A

The neurotransmitter

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25
Q

What opens the sodium channel ?

A

When the ligand binds to the receptor

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26
Q

What does the neuron have to depolarise to if its going to achieve an action potential ?

A

At least -55mV

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27
Q

What is the neuromuscular junction ?

A

The junction between the neuron and the muscle

28
Q

What is a failed initiation ?

A

Initiations where there is some depolarisation but it is insufficient to trigger an action potential

29
Q

What type of phenomenon is the triggering of an action potential ?

A

An all or nothing phenomenon

30
Q

What is a depolarisation ?

A

A change in voltage

31
Q

What opens behind the sodium channels ?

A

The voltage gated potassium channels

32
Q

What does the opening of the voltage gated potassium channels allow ?

A

Potassium ions to flow out to rapidly restore the charge separation

33
Q

How much intracellular potassium is there in the resting membrane potential verses the action potential ?

A

400mM verses 20

34
Q

How much extracellular sodium is there in the resting membrane potential verses the action potential ?

A

440mM verses 50

35
Q

What is the chemical trigger for neurotransmitter release ?

A

Calcium

36
Q

What is an excitatory post synaptic potential ?

A

The signal at the post synaptic site

37
Q

What happens when sodium channels are blocked with tetrodotoxin ?

A

The post synaptic and presynaptic potentials are progressively diminished across the time course of the tetrodotoxin treatment

38
Q

What contains tetrodotoxin ?

A

Puffer fish

39
Q

What does tetrodotoxin cause and why ?

A

Paralysis as it blocks all function at neuromuscular junctions

40
Q

What is an example of a potassium block ?

A

Tetraethylammonium

41
Q

How can the sodium influx be bypassed ?

A

By electrically depolarising the cell and the neurotransmitter still gets released and still stimulates the post synaptic cell

42
Q

What does the potassium block result in ?

A

The prevention of the normal repolarisation of the synaptic membrane

43
Q

What is potassium important in?

A

Repolarisation

44
Q

What are sodium and potassiums role in the release of neurotransmitters ?

A

Electrical

45
Q

What does depolarisation not produce in a calcium free medium ?

A

A post synaptic response

46
Q

What does increasing extracellular calcium increase ?

A

Neurotransmitter release

47
Q

As well as sodium and potassium channels, what other channels are there ?

A

Voltage dependent calcium channels

48
Q

Where must calcium be present to facilitate neurotransmitter release ?

A

Before or during the action potential

49
Q

What does dendrotoxin do ?

A

Blocks potassium channels

50
Q

Where is dendrotoxin found ?

A

Black mamba

51
Q

Where is latrotoxin found ?

A

Black widow spider

52
Q

What does latrotoxin produce ?

A

Massive acetylcholine release

53
Q

Where is alpha bungarotoxin found ?

A

Snake venom

54
Q

What does alpha bungarotoxin do ?

A

Blocks acetylcholine nicotinic receptor on skeletal muscle resulting in paralysis

55
Q

What are the steps in neurotransmitter release ?

A
  1. Sodium channels open
  2. Voltage change above 40mV - depolarisation
  3. Voltage dependent calcium channels open
  4. Low affinity calcium sensors in the active zone bind calcium
  5. Calcium dependent exocytosis
  6. Rapid turn off as calcium diffuses away from active zone
56
Q

Why does the concentration of calcium go very high for a short time ?

A

The synapse can rapidly buffer calcium - therefore must trigger its response quickly

57
Q

What are the four main factors influencing intracellular and extracellular concentrations ?

A
  1. Electrical gradients
  2. Chemical gradients
  3. Membrane permeability and leak channels
  4. Sodium/potassium ATPase
58
Q

What is equilibrium potential ?

A

The potential at which the chemical and electrical forces on a given ion are balanced and therefore is the potential at which this ion would cease to move across the membrane

59
Q

What is the phospholipid bilayer of the cell membrane highly impermeable to ?

A

Ions

60
Q

What is in the phospholipid bilayer of the cell membrane ?

A

Proteins embedded in the lipid bilayer

61
Q

What are ion channels ?

A

Proteins embedded in the lipid bilayer

62
Q

What do ion channels do ?

A

Allow for the highly specific passage of ions

63
Q

What do leak potassium channels allow ?

A

Potassium to flow through the membrane in response to the disparity in concentrations inside and outside the cell

64
Q

What contributes to the resting membrane potential of about -65mV ?

A
  1. Sodium/potassium ATPase

2. Potassium leak channels

65
Q

What is the threshold potential ?

A

The critical level to which a membrane potential must be depolarised to initiate an action potential

Cells to Organisms - Practicals (4 decks)

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