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Physiology > Potentials > Flashcards

Potentials Flashcards

1
Q

True/False: A diffusion potential is caused by diffusion of ions.

A

True

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2
Q

What depends on the size of the driving force?

A

Magnitude of DP

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3
Q

What depends on the charge of the diffusing ion?

A

Sign

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4
Q

What happens to the net diffusion of a diffusion potential when reaching equilibrium?

A

Ions slows and stops

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5
Q

What happens when a diffusion potential balances or opposes the tendency for diffusion?

A

Electrochemical equilibrium

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6
Q

What is used to calculate equilibrium potentials?

A

Nerst equation

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7
Q

What values go into calculating the nerst equation?

A

Charge on ion, constant 60 mV @37C, intracellular concentration, extracellular concentration

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8
Q

What is the typical equilibrium value of Na+?

A

+65 mV

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9
Q

What is the typical equilibrium value of K+?

A

-95 mV

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10
Q

What is the typical equilibrium value of Ca2+?

A

+120 mV

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11
Q

What is the typical equilibrium value of Cl-?

A

-90 mV

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12
Q

True/False: The driving force for charged solutions is the concentration difference.

A

False. Uncharged solutions

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13
Q

What does the driving force consider?

A

Potential difference of concentration and electrical potential difference (Em-Ex)

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14
Q

True/false: When the driving force is (+), that ion will enter the cell and if (-) it will leave the cell.

A

False. The opposite is true (-) to (+)

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15
Q

When does an ionic current (Ix) occur?

A

Movement across the CM

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16
Q

What is the formula for ionic current?

A

Ix= Gx(Em-Ex)

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17
Q

Ions will move across the CM to ion channels if there is what two things?

A

Conductance (Gx) and Driving Force (Em-Ex)

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18
Q

What is the potential difference that exists across a membrane of excitable cells in the period between action potentials (rest)?

A

Resting Membrane Potential

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19
Q

What is the typical range of resting membrane potential?

A

-70 to -80 mV

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20
Q

What is the phenomenon of excitable cells in which a rapid depolarization is followed by a rapid repolarization of the membrane potential?

A

Action Potential

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21
Q

Briefly discuss the ionic basis of action potential (in 4 steps).

A
  1. RMP is at -70mV. K+ conductance is high and channels are open for diffusion. 2. Inward current causes depolarization to thresholf (60 mV). Na+ activation gates open and depolarization occurs. 3. Upstroke is terminated and MP repolarizes to RMP from Na+ inactivation gates and depolarization opens K+ channels. 4. Undershoot of RMP to closer to Ek but eventually it returns to resting level, ready to go again.
22
Q

What is the toxin that blocks Na+ channels, preventing the occurence of APs?

A

Tetrodotoxin

23
Q

What blocks K+ channels resulting in no outward current of K+ so no repolarization?

A

Tetraethylammonium (TEA)

24
Q

What is responsible for the upstroke of AP in nerve and muscle?

A

Nerve Na+ channel

25
Q

What are the three gate positions?

A

Closed, but available. Open. Inactivated.

26
Q

When does the refractory period move from absolute to relative?

A

during undershoot

27
Q

True/False: Depolarization opens activation gates for Na+ for upstroke to occur.

A

False. Depolarization closes inactivation gates and upstroke cannot occur b/c of insufficient Na+ channels available

28
Q

What condition increases K+ serum in the body?

A

Hyperkalemia

29
Q

What does the increase of K+ do to the action potential?

A

Causes depolarization of RMP so the body is less likely to fire an AP from the Na+ gates being closed.

30
Q

Is the cell interior at rest negatively or postively charged?

A

Negatively

31
Q

Is the cell interior negatively or positively charged at depolarization?

A

Positively

32
Q

What is considered the speed at which an action potential is conducted along a nerve/muscle fiber?

A

Conduction Velocity

33
Q

True/False: Conduction velocity determines the speed at which info is transmitted to the nervous system?

A

True

34
Q

What are the two cable properties that influence conduction velocity?

A

Time constant and length constant

35
Q

What two things affect the time constant?

A

Membrane Resistance and Membrane capacitance

36
Q

What two things affect the length constant?

A

Membrane resistance and internal resistance

37
Q

Ultimately, the __ the membrane resistance and the __ the membrane conductance results in higher conduction velocity.

A

Lower, Higher

38
Q

Ultimately, the __ the membrane resistance, the ___ the diameter, and the __ the internal resistance, the higher the conduction velocity is.

A

higher, smaller, lower

39
Q

What two mechanisms can increase conduction velocity?

A

Myelination and increasing nerve diameter

40
Q

A man sustains a burn to over 60% of his body, which leads to a decrease in the serum [K+] from normal (4) to 2.5 Eq/L. What happens to the RMP and K+ Nernst Potential in the cardiac myocyte after the injury?

A

RMP = more negative, K nernst potential = more negative.

41
Q

Where does potassium conductance exceed sodium conductance?

A

At rest and after repolarization

42
Q

What happens during the upstroke of the nerve action potential?

A

Net inward current and cell interior becomes less negative

43
Q

What is responsible for the change in membrane potential occurring between RMP and Ena+ depolarization?

A

Movement of Na into cell

44
Q

What is responsible for the change in membrane potential between depolarization and repolarization?

A

Movement of K+ out of the cell

45
Q

What would increase the velocity conduction of APs along a nerve?

A

Myelinating the nerve (also, increasing the diameter)

46
Q

What are the three characteristics of action potentials?

A

Stereotypical size and shape, propagation, and all-or none response

47
Q

What happens during the hyperpolarizing afterpotential?

A

Following repolarization when the MP is more negative than at rest. Another word = undershoot

48
Q

What is overshoot?

A

Period of AP when it is more positive (depolarization)

49
Q

What is the meaning of the term influx?

A

Positive charge entering the cell

50
Q

What is the meaning of the term outflux?

A

Positive charge leaving the cell

Physiology (11 decks)

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