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Physiology Block 5 > Ionic Movement, Membrane Potentials, And Action Potentials > Flashcards

Ionic Movement, Membrane Potentials, And Action Potentials Flashcards

1
Q

Permeability of cell membrane

A

Selectively permeable

-some things can diffuse through membrane (small, non polar molecules, steroids, oxygen)

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2
Q

Most solutes in the body and the cell membrane

A

Most solutes in body are large and/or charged and cannot cross the membrane

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3
Q

Conductance is by use of what?

A

Transport porteins and ion channels

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4
Q

Amount able to cross membrane is based on what?

A

Number and activity of these proteins

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5
Q

_____ are small holes that allow specific size/charge of ion to cross

A

Ion channels

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6
Q

Conductance of ions is based on what

A

The number of channels that are ‘open’

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7
Q

Ion channels and ionic movement are specific to what

A

Ionic size and charge

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8
Q

Size example of size exclusion in ion channel

A

A sodium channel can exclude a calcium/potassium ions due to different molecule size

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9
Q

charge exclusion in ion channel

A

Interior of channel will be lined with charged amino acids, will prevent like ions from crossing

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10
Q

Flow of ions depends on what?

A

Number of open channels

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11
Q

Leak channels

A
  • always open

- some K+ channels and Cl- channels

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12
Q

Examples of gated channels

A

Ligand, 2nd messenger, voltage, mechanical, light, etc

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13
Q

These types of gates remain closed until proper ligand is present

A

Ligand gated

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14
Q

These types of ligands remains open as long as ligand is around, closes when removed

A

Ligand gated

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15
Q

Example of ligand gated channels

A

Nicotinic receptors in skeletal muscles neuromuscular junction
-binds acetylcholine, allows Na+ (mostly) and K+ (little) to flow down gradients

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16
Q

What type of channel remains open as long as 2nd messenger is around, closes when removed?

A

2nd messenger gated

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17
Q

How much messenger will be made until when?

A

Until receptor is no longer stimulated

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18
Q

Example of 2nd messenger gated channel

A

Ca2+ channels in smooth muscle cells. Angiotensin II binds to its receptor causing production of IP3 which binds to and open Ca2+ channels (InsP3R)

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19
Q

What type of channel remain closed until membrane potential reaches specific value?

A

Voltage gated

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20
Q

What type of channel remains open depending on the membrane potential and channel properties?

A

Voltage gated channels

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21
Q

Example of voltage gated channels

A

Sodium channel (Nav) in muscles. Once membrane potential gets above certain point, they open. When it reaches a 2nd set point, they close

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22
Q

Which type of channel would have the most rapid effect on ionic flow?

A

Ligand gated

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23
Q

What type of channel could lead to a more varied cellular response?

A

2nd messenger

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24
Q

What happens when ions move down a concentration gradient?

A

They generate a current

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25
Q

What is diffusion potential?

A
  • measured in mV

- only moves until the charge changes, not big change in concentration

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26
Q

Potential difference (charge) required to stop ionic movement

A

Equilibrium potential

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27
Q

Ions move in response to what?

A

Concentration and charge

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28
Q

How many ions need to move to make a charge difference across a membrane?

A

Very few

Basis for resting membrane potential and the nervous systme

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29
Q

What does movement of charged particles generate?

A

An electrical potential

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30
Q

What equation do we use to determine the equilibrium potential?

A

Nernst equation

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31
Q

What does the charge on each ion (Ena=+65mV) mean?

A

Inside of cell membrane is negative at rest. Must equal this number to make it permeable to that specific ion

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32
Q

Driving force

A

mV=Em-Ex

EM is actual membrane potential
Ex is equilibrium potential

Na+
mV=-70-65. mV=135

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33
Q

Ionic current: GX (driving force)

A

Hx=conductance (measure of the # of open channels)

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34
Q

Account for what to get the resting membrane potential (RMP)

A

Account for all ionic concentration gradients and membrane permeability and you get the resting membrane potential (RMP)
-Goldman equation or chord equation

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35
Q

Charge difference across cell membranes due to concentration gradients of permanent ions

A

Resting membrane potential

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36
Q

What does each ion try to do to the RMP?

A

Tries to push it towards its own Eq potential

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37
Q

Inside of cell is considered ______ compared to outside of cell

A

Negative

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38
Q

What is the charge of the inside of the cell

A

Ranges from -20 to -100mV

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39
Q

What kind of tissue can rapidly change the RMP to send signals and start conduction?

A

Excitable tissue (muscle and nerves)

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40
Q

Increasing permeability of ________ to 100% would likely result in the greatest change in resting membrane potential

A

Calcium (+120)

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41
Q

Rapid changes in membrane potential

A

Action potential

42
Q

What do action potentials consist of?

A

Depolarization from RMP and repolarization to RMP

43
Q

Types of actions potentials in different tissues

A

All APs look the same in similar tissue, but the AP of two different tissues is different

44
Q

When does AP occur?

A

An AP either occurs or it does not

  • all or none
  • if membrane reached specific voltage (threshold) then an AP will occur
45
Q

Stages of action potential: at rest

46
Q

Stages of action potential: local depolarization

A

Membrane moves closer to 0mV

47
Q

Stages of the action potential: threshold (about -60mV)

A

Point at which AP has to occur

48
Q

Stages of the action potential: overshoot

A

Interior becomes + relative to outside

49
Q

Stages of the action potential: repolarization

A

Membrane begins to move back towards 0 and negative

50
Q

Stages of action potentials: hyperpolarization

A

Membrane becomes more negative

51
Q

Stages of action potential: at rest

A

RMP is reattained

52
Q

What are the steps of action potential

A 
Rest
Local depolarization
Threshold
Overshoot
Repolarization
Hyperpolarization
Rest
53
Q

Membrane potential at rest

54
Q

What is the RMP maintained by?

A

K+ leak currents (Eq is about -85)

Dependent upon K+ conductance

55
Q

What is necessary for RMP?

A

Na-K ATPase

  • 3Na+ out
  • 2K+ in
  • more negative now
  • maintains large K+ gradient so small flux can occur and generate the RMP
56
Q

Stability of RMP

A

Stable in most cell types

-unstable in rhythm generating cells (heart/intestines)

57
Q

What is the major contributor to RMP?

A

K+ current through leak channels

58
Q

Local depolarization

A
  • stimulation occurs-usually gated Na+ channel
  • local membrane moves closer to 0mV
  • stimulated
59
Q

Local hyperpolarization

A

Stimulation occurs-usually ligand gated Cl- channels

  • local membrane becomes more negative
  • inhibited
60
Q

Where is the threshold?

A

About -60mV

61
Q

Threshold

A
  • IF local depolarization reaches this level, then action potential HAS to occur
  • voltage gated Na+ channels open
62
Q

What is responsible for the depolarization of AP?

A

Voltage gated Na+ channels (Nav)

-rapidly opened and closed due to two sets of gates

63
Q

What are the two sets of gates in voltage gated sodium channels?

A

Inactivation

Activation

64
Q

Where is the inactivation gate for the voltage gated sodium channels?

65
Q

Where is the activation gate for the voltage gated sodium channel?

66
Q

At rest, what is the state of the two voltage gated sodium channels?

A
  • activation is closed

- inactivation is open

67
Q

When is the activation gate of the voltage gated sodium channel open?

A

At threshold

68
Q

When is the inactivation gate of the voltage gated sodium channel closed?

A

At overshoot

69
Q

What is required for action potential?

A

Voltage gated sodium channels

70
Q

If the voltage gated sodium channels ar blocked, what happens?

A

No AP will occur, paralysis

71
Q

What are some examples of things that block voltage gated sodium channels and cause paralysis?

A

Tetrodotoxin (blowfish)

Lidocaine

72
Q

Overshoot is due to what

A

Rapid influx of Na+

73
Q

Where does overshoot usually peak?

74
Q

What happens at overshoot?

A

Inactivation gate closes, no more Na+

75
Q

What kind of channels open at overshoot?

A

Voltage gated K+ channels open

76
Q

How many gates are involved with voltage gated K+ channels?

A

One

Much slower to close

77
Q

What happens when the voltage gated K+ channels open?

A

K+ flux out of cell begins to repolarize

  • losing positive charges
  • blocked by TEA
78
Q

What happens are repolarization

A
  • Na conductance slows, K conductance rises

- more positive charges leave the cell

79
Q

What happens are hyperpolarization

A
  • membrane becomes more negative than RMP

- will hyperpolarize closer to the K+ Eq point

80
Q

When is RMP re-established?

A

As K+ gates close

-leak channels and Na-K ATPase

81
Q

When is there a K+ flux through leak channels?

A

At rest RMP

82
Q

When does stimulation occur-ligand gated Na channel?

A

Local depolarization

83
Q

When do Nav channels open?

A

Threshold (about -60mV)

84
Q

When is there a Na+ flux?

85
Q

When does Na+ slow and K+ rise?

A

Repolarization

86
Q

When is there more K+ leaving?

A

Hyperpolarization

87
Q

When is RMP re-established?

A

Due to K+ leaks

88
Q

RMP and APs are based on what

A

Ionic gradients

-at rest, only open channels are K+ so RMP is sensitive to alterations in plasma levels

89
Q

Too much K

A

Hyperkalemia

  • less negative
  • hypopolarizes RMP(more positive)
90
Q

Not enough K

A

Hypokalemia

-higher gradient-hyperpolarizes (more neg) RMP

91
Q

Slowly depolarizing and AP

A

Can stop APs from being generated

92
Q

What does slow depolarization occur due to?

A

Inactivation gates closing before activation opens

No Na+ no AP

93
Q

What is accommodation of AP?

A

Inactivation gates closing before activation opens (no Na+ no AP)

  • can be the result of persistent hyperkalemia
  • decreased gradient, raises RMP towards 0
94
Q

No AP = what?

A

Paralysis of muscles, death

95
Q

The more K+

A

present, the less negative the membrane potential

96
Q

Which of the following could be a consequence of acute hyperkalemia

A

Less steep repolarization slope

Increases K, more positive

97
Q

What affect would hypernatremia have on the RMP?

A

No change
No sodium channels open at rest
-almost no affect on RMP

98
Q

What are APs used for?

A

To send information

99
Q

What are refractory periods due to

A

Cells inability to depolarize again

-channels not reset

100
Q

Absolute Refractory period

A

No AP

-activation gate of NA, not closed

101
Q

Relative refractory period

A

Need a greater than normal stimulus

-Kv flux hyperpolarizes cell, harder to get to threshold

Physiology Block 5 (8 decks)

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