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Physiology > Potentials > Flashcards

Potentials Flashcards

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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).

Study These Flashcards
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?

23
Q

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

Study These Flashcards
A

Tetraethylammonium (TEA)

24
Q

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

Study These Flashcards
A

Nerve Na+ channel

25
What are the three gate positions?
Closed, but available. Open. Inactivated.
26
When does the refractory period move from absolute to relative?
during undershoot
27
True/False: Depolarization opens activation gates for Na+ for upstroke to occur.
False. Depolarization closes inactivation gates and upstroke cannot occur b/c of insufficient Na+ channels available
28
What condition increases K+ serum in the body?
Hyperkalemia
29
What does the increase of K+ do to the action potential?
Causes depolarization of RMP so the body is less likely to fire an AP from the Na+ gates being closed.
30
Is the cell interior at rest negatively or postively charged?
Negatively
31
Is the cell interior negatively or positively charged at depolarization?
Positively
32
What is considered the speed at which an action potential is conducted along a nerve/muscle fiber?
Conduction Velocity
33
True/False: Conduction velocity determines the speed at which info is transmitted to the nervous system?
True
34
What are the two cable properties that influence conduction velocity?
Time constant and length constant
35
What two things affect the time constant?
Membrane Resistance and Membrane capacitance
36
What two things affect the length constant?
Membrane resistance and internal resistance
37
Ultimately, the __ the membrane resistance and the __ the membrane conductance results in higher conduction velocity.
Lower, Higher
38
Ultimately, the __ the membrane resistance, the ___ the diameter, and the __ the internal resistance, the higher the conduction velocity is.
higher, smaller, lower
39
What two mechanisms can increase conduction velocity?
Myelination and increasing nerve diameter
40
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?
RMP = more negative, K nernst potential = more negative.
41
Where does potassium conductance exceed sodium conductance?
At rest and after repolarization
42
What happens during the upstroke of the nerve action potential?
Net inward current and cell interior becomes less negative
43
What is responsible for the change in membrane potential occurring between RMP and Ena+ depolarization?
Movement of Na into cell
44
What is responsible for the change in membrane potential between depolarization and repolarization?
Movement of K+ out of the cell
45
What would increase the velocity conduction of APs along a nerve?
Myelinating the nerve (also, increasing the diameter)
46
What are the three characteristics of action potentials?
Stereotypical size and shape, propagation, and all-or none response
47
What happens during the hyperpolarizing afterpotential?
Following repolarization when the MP is more negative than at rest. Another word = undershoot
48
What is overshoot?
Period of AP when it is more positive (depolarization)
49
What is the meaning of the term influx?
Positive charge entering the cell
50
What is the meaning of the term outflux?
Positive charge leaving the cell

Physiology (11 decks)

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