NEUR 2035 Midterm - Lab 3 Flashcards
When an ion inside and outside reaches a balanced state (with no net movement), the chemical (diffusional) force is exactly offset by its electrical force.
True or False:
This balance point is known as the reversal potential (or equilibrium potential) for that ion.
True
Cell membrane potential becomes ____ during hyperpolarization.
More negative
Which ion has the highest concentration inside a neuron?
A. Calcium
B. sodium
C. potassium
D. chloride
C
True or false:
A sodium ion can pass through a potassium ion channel freely because it is much smaller than a potassium ion.
False
Which ion has the lowest concentration inside a neuron?
A. chloride
B. sodium
C. potassium
D. calcium
D
1 mM sodium means…
A. 0.01 moles sodium per liter
B. 0.001 moles sodium per liter
C. 0.1 moles sodium per liter
D. 1 mole sodium per liter
B
Cell membrane potential becomes ____ during depolarization.
Less negative
Which ions have a higher concentration in the extracellular fluid than in the intracellular fluid?
A. calcium
B. potassium
C. sodium
D. chloride
A, C, D
Cell membrane potential becomes ____ during repolarization.
More negative
True or false:
The opening or closing of leaky potassium channels is controlled by changes in the membrane potential (voltage).
False
What does membrane potential refer to?
A. the amount of current that can flow out of a cell
B. the potential of the cell membrane
C. the amount of ions that can cross the cell membrane
D. the voltage difference across the cell membrane
D
True or false:
A cell can have different membrane potentials at different spots on its cell membrane.
True
How will positive ions move if the membrane potential is more negative than the ion’s reverse potential?
A. They will move out of the neuron
B. They will move into the neuron
C. There will be no ion movement
B
True or false:
EPSP can always cause an action potential, while IPSP always inhibits an action potential.
False
If a positively charged ion has an extracellular concentration of 10mM, an intracellular concentration of 100nM, and its equilibrium potential is -65mV:
A. the ion will flow in
B. we cannot determine the behavior
C. the ion will flow out
B
Which variables are needed to calculate the equilibrium potential of an ion?
A. extracellular concentration
B. charge
C. intracellular concentration
D. permeability
E. temperature
A, B, C, E
True or false:
When calculating using the Nernst equation, we use the constants that we get for the current temperature times ([X]outside/[X]inside).
False
An ion with zero permeability but ten times higher concentration extracellular compared to intracellular, based on the Goldman equation, this ion ____ affect the membrane potential.
Will not
True or false:
In hot weather, compared to cooler weather (without air conditioning), our body temperature will increase slightly. This increase also raises the cell membrane potential, even with the same concentration and permeability of ions. This increase makes neurons more likely to reach action potential. Therefore, in hot weather, people tend to be more reactive to stimuli.
True
What is the ratio for every sodium and potassium ion to leave and enter the neuron while the sodium-potassium pump is working?
A. 2 sodium enter / 3 potassium leave
B. 3 sodium enter / 2 potassium leave
C. 3 sodium leave / 2 potassium enter
D. 2 sodium leave / 3 potassium enter
C
How would an elevated extracellular potassium concentration impact potassium’s reversal potential?
It would become less negative
How would an elevated extracellular potassium concentration affect the propagation of action potentials?
Membrane potential would become more positive, increasing excitability
How would a low extracellular sodium concentration affect sodium’s equilibrium potential?
It would become more negative
How would a low extracellular sodium concentration affect the propagation of action potentials?
Lower magnitude EPSPs would lead to fewer action potentials
How would a high extracellular sodium concentration affect sodium’s equilibrium potential?
It would become more positive
How would a high extracellular sodium concentration affect the propagation of action potentials?
Higher magnitude EPSPs would result in more action potentials
With all other factors being equal, why would a “Small EPSP” be small and a “Large EPSP” be large?
More neurotransmitters were involved in triggering the Large EPSP
With all other factors being equal, is a “Large EPSP” or a “Small EPSP” more likely to result in the propagation of an action potential?
Large EPSP
How could a “Small EPSP” trigger an action potential when a “Large EPSP” fails to do so?
If the Small EPSP occurred closer to the axon hillock
If the threshold potential is -51.5 mV, and an EPSP has a magnitude of -61.1 mV, will the neuron spike? Why or why not?
No, because the EPSP does not reach threshold
Using reversal potentials and permeabilities, explain why the membrane potential becomes more positive during depolarization and more negative during repolarization.
Depolarization - increased Na permeability causes Na to flow towards its reversal potential which is positive
Repolarization - increased K permeability causes K to flow towards its reversal potential which is negative
During action potentials, why don’t the lower and upper limits of membrane potential change exceed the reversal potentials for sodium and potassium?
If this happened, the ions would reverse their net flow
What would happen to the sodium current if the membrane potential were more positive than its reversal potential?
The flow of sodium ions would reverse
How does an increase in sodium conductance affect the EPSP?
Makes the current of the EPSP stronger
Why is the sodium current negative during an EPSP?
The amount of ions flowing in is mathematically negative
(ions are flowing out)
What would happen if chloride’s reversal potential was the same as the resting membrane potential?
There would be no chloride current
How does an increased chloride conductance affect the likelihood of generating an action potential?
Makes it less likely
What effect would opening additional chloride channels have on the membrane potential?
It would result in an increased chloride conductance, thus hyperpolarizing the membrane and making an action potential less likely
How do opposing sodium and chloride charges influence the overall membrane potential?
Sodium depolarizes and chloride hyperpolarizes
How does the balance of excitatory and inhibitory inputs shape neuronal activity?
It determines if an action potential will fire
Why does the sodium current remain inward during depolarization?
Membrane potential is more negative than sodium’s reversal potential
What role does potassium conductance play in limiting the extent of depolarization?
Since there is some conductance, sodium can’t reach its reversal potential
How would the action potential change if the potassium conductance increased earlier?
There would be a lower magnitude of depolarization
Why is the potassium current positive during repolarization?
Potassium ions are leaving the cell
What would happen to membrane potential if the sodium channels did not inactivate during repolarization?
It would be unable to return to resting potential
How does the timing of potassium conductance changes help restore the resting potential?
Sodium conductance must decrease for repolarization to occur
Potassium conductance must decrease for membrane potential to return to rest
What factors determine the extent of hyperpolarization in neurons?
- Ion conductances
- Membrane potential
- Duration of channel openings
Why does potassium conductance remain high during hyperpolarization, and how does this affect neuron excitability?
Potassium channels are slow to close, which makes the neuron less excitable
How would increasing extracellular potassium levels affect the extent of hyperpolarization?
It would reduce it
What role does hyperpolarization play in preventing the immediate firing of another action potential?
Makes it more difficult to fire an action potential
