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A&P 2024 > Lecture 4/5 > Flashcards

Lecture 4/5 Flashcards

Exam 2

1
Q

Where does the intracellular sodium come from for the Na/K ATPase pump?

A
  • Sodium is allowed into cell via secondary active transport processes (3Na+/1Ca++ exchange)
  • Sodium leakage at rest (simple diffusion)
  • Action potential - sodium comes in
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2
Q

Where does the intracellular water come from?

A

Aquaporins allow water to easily move both ways across cell membrane

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3
Q

Describe the cell diuretic feature and its involvement in the Na/K ATPase pump

A

Keeps cell osmolarity in check - moves water ICF → ECF with sodium
- responsible for intracellular volume control

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4
Q

Describe cellular edema and how to fix it

A

Sick patient low on ATP → Na/K ATPase pump doesn’t work as well → ICF increases → swelling
- Very hard to fix, have to fix cellular ATP levels in order to fix problem

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5
Q

How does the Na/K ATPase pump influence calcium levels?

A

Secondary active transport - provides the extracellular sodium in sodium calcium exchange (NCX) transporter

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6
Q

Describe how the Na/K ATPase pump works against the electrochemical gradient

A

Na+ movement is against concentration and electrical gradient
K+ movement is only against concentration gradient

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7
Q

How much ATP is used in one round of Na/K ATPase pump?

A

1 ATP

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8
Q

Compare a graph of facilitated vs simple diffusion rates

A
  • Simple diffusion increases linearly w/ increases in [] gradient.
  • Facilitated diffusion increases w/ increased [] gradient until all transporter proteins are saturated and transporting as fast as possible.
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9
Q

What is the Vmax in facilitated diffusion? Why is there a Vmax?

A

Vmax - max speed the transporters can diffuse
- conformation change can only happen so fast

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10
Q

Why is there not a Vmax in simple diffusion?

A

Not a Vmax with simple diffusion because no conformation change; depends on electrochemical gradient

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11
Q

What are the 8 factors that effect diffusion rate?

A
  1. [Concentration]inside vs [Concentration]outside cell (chemical gradient)
  2. Membrane (lipid) solubility
  3. Size of the particle
  4. Size of the pores for travel
  5. # of pores for travel
  6. Kinetic movement (heat)
  7. Physical pressure
  8. Electrical charge
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12
Q

What is osmotic pressure?

A

Osmotic pressure is the physical pressure (force) required to prevent osmosis from occurring through a semipermeable membrane into an osmotically-active solution.

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13
Q

How does osmotic pressure relate to osmolarity?

A

1 mOsm = 19.3 mmHg in 1L

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14
Q

What is the difference between osmolarity and osmolality?

A

Osmolarity - liters
- more practical
Osmolality - kg

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15
Q

What is Vrm?

A

Resting membrane potential (mV)

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16
Q

At rest, excitable cells are ______ compared to conditions outside of cell

A

Electronegative

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17
Q

When an excitable cell is “on” it is _______ inside the cell. When an excitable cell is “off” it is _______ inside the cell

A

Positive, negative

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18
Q

What causes resting membrane potential?

A

Na/K pump and selective permeability of membrane (distribution of proteins)

differences in the concentrations of ions (particularly Na/K) inside and outside the cell

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19
Q

How does protein concentration impact Vrm?

A
  • [Protein]i&raquo_space; [Protein]o - more proteins inside cell wall than outside cell wall
  • Proteins often carry a net negative charge.
  • Proteins are also an important intracellular buffer
  • Many proteins aligned at the cytosolic face of the cellular membrane.
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20
Q

What charge do proteins usually have? Why?

A

Proteins are made from amino acids (more (-) amino acids than (+)) → proteins typically have net negative charge
- makes ICF (-)

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21
Q

Recite the Nernst (equilibrium) Potential equation

A

EMF = (+/-)61 x log([inside]/[outside])

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22
Q

What is the nernst potential?

A

Nernst Potential is the voltage that will prevent ions from diffusing across the membrane, down their concentration gradients.

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23
Q

At rest, what ions is the cell permeable to?

A

Sodium and potassium

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24
Q

Which ion influences resting membrane potential the most?

A

Potassium - permeability at rest to potassium is 10x more than sodium (P(Na) < P(K))

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25
Q

At rest, K+ is _______ the cell

A

Leaving
- Wants to go from area of higher concentration to lower

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26
Q

At rest, Na+ is _______ the cell

A

Entering
- Wants to go from area of higher concentration to lower

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27
Q

Describe how the EMF of potassium effects the polarity of the cell (EMF = -90 mV)

A

Potassium leaving the cell will cause the ICF charge to become more electronegative

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28
Q

Describe how the EMF of sodium effects the polarity of the cell (EMF = 61 mV)

A

Sodium entering the cell will cause the ICF to become more positively charged

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29
Q

Overall membrane potential of the cell will be ______

A

closer to K+ → -80 mV

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30
Q

If an excitable cell wants to become active, it will allow more ______ to enter the cell

A

Sodium - makes ICF more positively charged (depolarization)

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31
Q

What is the difference between the Nernst and Goldman equations?

A

Nernst - membrane potential for 1 electrolyte
Goldman - membrane potential for multiple ions; dependent on concentration and permeability of individual electrolytes

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32
Q

How does the Goldman equation relate ion concentration and permeability?

A

Each [ion] gradient contributes only as much as the membrane is permeable to each ion.

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33
Q

Cell adjusts ________ to adjust the membrane potential

A

ion permeability (ion channels)

34
Q

mEq/solution and mOsm/solution are a measurement of

A

quantity/volume

35
Q

The reason that not all of the water in the U shape test tube flows to one side despite there being no solute on one side is ____________

A

gravity

36
Q

The net ion change for one cycle of the sodium potassium ATPase pumps is

A

ICF becomes (-) by the charge of 1 ion with one cycle of a single Na K ATPase cycle (loses 3+, gains 2+)

37
Q

Water follows ______

A

sodium

38
Q

What happens to the membrane potential of a cell if the concentration of ICF:ECF of potassium decreases?

A

The lower end of the membrane potential will be higher (-70 instead of -90), making the overall resting membrane potential higher (-60 instead of -80)

39
Q

What channels determine the action potential?

A
  • Voltage-gated “Fast” Na+ channels, depolarization
  • Voltage-gated “slower” K+ channels, repolarization
40
Q

What is the membrane potential when sodium rushes in and the cell hits action potential?

A

+35

41
Q

What will high K+ do the the heart?

A

EKG changes (V-fib) - lowers the rate of repolarization because the ICF is less (-)

42
Q

What cells are highly permeable to chloride ions?

A

Neurons

43
Q

Is a more electronegative resting membrane potential easier or harder to excite than a more electropositive RMP?

A

more negative = harder (hyperpolarization)
more positive = easier

44
Q

RMP and permeability is dependent on ________, not ________

A

Diffusion through channels, not Na+/K ATPase pump

45
Q

Resting cells are said to be ________

A

Polarized (-mV @ Vrm)

46
Q

A difference in electrical charge between inside and outside of cell is __________

A

Polarization

47
Q

To become less polar (or more + charged); usually = stimulated or turned on is ________

A

Depolarization

48
Q

To become more polar (or more–charged) than Vrm; usually = inhibited (or more–charged and more difficult to excite __________

A

Hyperpolarization

49
Q

__________ is to return to Vrm from a depolarized state

A

Repolarization

50
Q

Hyperpolarization can occur when?

A

At rest (change in permeability) or after depolarization

51
Q

Why doesn’t depolarization reach +60mV?

A

Because K+ channels never fully close

52
Q

What is the purpose for the plateau in action potentials in the heart?

A

Action potential sustained longer
- period of time spent in action potential decides how well heart is going to pump (myocardial muscle contraction)

53
Q

What is conductance?

A

How much ion flow or how much potential current does the cell have
- inverse of resisitence
- the relative ease at which an ion can cross the membrane

54
Q

During repolarization, the cell opens _______ to speed up the process

A

Additional K+ channels (Voltage-Gated) until back to RMP

55
Q

Why does hyperpolarization occur?

A

Result of extra K+ channels staying open until return to RMP

56
Q

Why would the cells want to repolarize the cell quickly?

A

Send messages quickly (nervous system)

57
Q

___________ results in more V-G Na+ channels opening during depolarization

A

Positive feedback

58
Q

What causes the plateau of depolarization of action potentials in the heart?

A

Influx of calcium

59
Q

How positive would the membrane potential need to be to prevent Na+ from entering the cell?

A

+61 mV

60
Q

How negative would the membrane potential need to be to prevent K+ from leaving the cell?

A

-90 mV

61
Q

A RMP of -80 mV prevents ______ even though there is relatively high permeability

A

K+ from leaving the cell; because (+) want to stay in (-)

62
Q

A RMP of -80 mV encourages ______ even though there is relatively low permeability

A

Na+ to enter the cell; because (+) wants to move towards (-)

63
Q

Cell membrane doesn’t actually need current, cells just need the ________

A

Potential for current

64
Q

Usually, the potential for current ends up creating _______

A

Current

65
Q

If an electrolyte with a negative charge has an equilibrium potential of -50 mV, what would the electrical/concentration gradient look like if the Vrm is -80 mV?

A

Higher concentration outside
Vrm would push the electrolyte out of cell

66
Q

What is equilibrium potential?

A

The charge required in the inside of the cell to prevent the movement of an ion down its concentration gradient (+61 mV for Na+)

67
Q

Any drug that ends in _______ effects the V-G Na+ channels

A
  • caine (many anesthetics)
68
Q

What are the different V-G sodium gates doing at rest?

A

Activation/Outside gate - closed at rest (M-gate)
Inactivation/Inside gate - open at rest (H-gate)

69
Q

In V-G Na+ channels, as the activation gate is opening, this triggers the ________

A

Inactivation gate to close

70
Q

After polarization, the membrane must ________ to open the inactivation gate.

A

Repolarize

71
Q

If you don’t have normal resetting after an action potential, the cell won’t be able to ______

A

Refire

72
Q

When repolarizing, the activation gate has to ______ first and then the inactivation gate ______

A
  1. Close the activation gate
  2. Reopen the inactivation gate
    - if not in this order, both gates would be open and sodium would rush in
73
Q

V-G K+ channels are _______ to open than the Na+ channels

A

Slower - also slower to close (hyperpolarization)

74
Q

At rest, the V-G K+ gate is _______

A

Closed

75
Q

_______ opens the V-G K+ gate

A

Depolarization

76
Q

The nicotinic (ACh-R) channel/receptor is an example of _________

A

Depolarizartion
- 2 ACh bind nACh-R
- Negatively-charged ion pore opens.
- Positive ions flow in
- More Na+ flows in than K+ flows out

77
Q

The muscarinic (mACh-R) is an example of ________

A

Hyperpolarization
- AV Node in heart
- GPCR is coupled directly to a K+ channel.
- More K+ channels open: more polar
- More polar = hyperpolar(ized)

78
Q

The driving force of an ion depends on 3 things:

A

charge of ion, concentration gradient of ion, and charge of ICF

79
Q

What channels are usually effected by anesthetic drugs?

A

Fast Na+ channels - make it harder to reset itself

80
Q

V-G K+ channel gates are located on the ______ of the cell

A

inside

A&P 2024 (19 decks)

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