BISC 230Lgx Lecture Notes - Lecture 5: Membrane Potential, Resting Potential, Cell Membrane

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9 Apr 2016

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Equilibrium: is reached when the concentraion gradient is equal and opposite to the charge gradient. Two forces are on the ions: electrical force, and concentraion force, which create voltage (separated charge) Measuring a neuron"s resing potenial/voltage: o o o. Insert a microelectrode into a resing cell, and compare with a second electrode outside the cell. Neuron resing potenial: commonly -60 millivolts, or . 06 v (compared to 1. 5 v batery) Inside of the axon is negaive, outside is posiive if voltage is negaive, the inside is more negaive than the outside. Big molecules inside the cell (proteins) are negaive and cannot pass through the cell membrane. Pushes na+ ions out of the cell, pulls k+ ions in. K+ ions can pass through channels in membrane down the concentraion gradient. Na+ ions cannot go back into the cell. Equilibrium potenial: the voltage that balances the concentraion gradient (is the same as the resing potenial of the cell).

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6. Consider the presence of hemoglobin in the catheter bag. Whatsymptom would this loss of

hemoglobin most strongly and immediately be linked to in thepatient?

A. Loss of blood volume

B. Loss of heartbeat

C. Drop in blood oxygen saturation

D. Liver failure

When a neuron is stimulated, the area of the membrane at thepoint of stimulation becomes

more permeable to Na+. If a cell starts at resting potential(-70mv), and is then stimulated:

A. The membrane voltage will become < -70mV, because Na+will move OUT of the cell.

B. The membrane voltage will become > -70mV, because Na+will move OUT of the cell.

C. The membrane voltage will become < -70mV because Na+will move INTO the cell.

D. The membrane voltage will become > -70mV because Na+will move INTO the cell.

. At the peak of the action potential, the Na+ voltage-gatedchannels close, and K+ voltage-gated

channels open in response to the positive membrane potential.In order to return the cell to its

negative resting potential quickly:

A. K+ will diffuse along its concentration gradient INTO thecell.

B. K+ will diffuse along its concentration gradient OUT of thecell.

C. Na+ will reverse its direction of diffusion OUT of thecell.

D. The sodium-potassium pump will move Na+ OUT of the cell andK+ INTO the cell.

E. None of the above would return the cell to its negativeresting potential quickly.

You experiment with higher concentrations of toxin and findcases when the cell could not

repolarize at all or, if it began to repolarize, itimmediately depolarized again. This tells you that

the toxin:

A. Prevents voltage-gated K+ channels from opening.

B. Increases the speed that the Na+ ion channels open.

C. Prevents the Na+ ion channels from closing.

D. Makes the Na+ ion channels close too soon.

E. Doesn

lavenderclam549

1. The plasma membrane of rod and cone cells are

a) At resting potential in the dark and deploarized in thelight

b) At resting pootential in the dark and hyperpolarized in thelight

c) Depolarized in the dark and hyperpolarized in the light

d) Hyperpolarized in the dark and at resting potential in thelight

e) Hyperpolarized in the dark and depolarized in the light

2. The equilibrium potential of K+ ions in nerve cells is about-90mV. The membrane potential of a typical nerve cells at rist is-70mV. Therfore

a) Increasing the permeability of a resting neuronal membrane toK+ ions will increase the membrane potential (that is, make it morenegative, inside with respcect to outside)

b) In nerve cells at rest, there is a net diffusion of K+ ionsout of the cell

c) Increasing the membrane potential of a nerve cell would slowthe diffusion of K+ ions out of it.

d) K+ is not the only ion that is permeable at rest

e) All of the above

3. Which of the following is responsible for the replarizingphase of the action potential?

a) Voltage-gated Na+ channels are opened.

b) The Na+-K+ pump restores the ions to theri original restingstate.

c) The permeability to Na+ increases greatly.

d) ATPase destroys the energy supply that was maintaining theaction potential at its peak.

e) The permeability to K+ increases greatly while that to Na+decreases

4. The Relative refractory period of an axonm conincides withthe period of

a) Activation and inactivatioin of voltage-gated Na+channels

b) Increased Na+ flux into the cell

c) Increased K+ flux into the cell

d) Increased K+ flux out of the cell

e) Increased Na+ flux out of the cell

5. The plasma membranes of rod and cone cells are

a) At resting potential in the dark and epolarized in thelight

b) At resting potential in the dark and hyperpolarized in thelight

c) Depolarized in the dark and hyperoplarized in the light

d) Hyperpolarized in the dark and tat resing potential in thelight

e) Hyperpolarized in the dark and depolarized in the light

**Please only answer if you are 100% correct!

1. Why are Na+, K+, and Clâ the only ions considered in the GK equation when calculating resting membrane potential (Vm)?

A. These ions are found in the highest concentrations inside the cell

B. These are the ions to which cell membranes are permeable at rest

C. Only these ions have enough charge to influence Vm

D. These ions bind to receptors that increase the charge on the membrane

2. Voltage-regulated channels are located

A. on the neuron cell body only

B. within the cytosol only

C. in the membranes of axons only

D. in the membranes of dendrites only

E. in the membranes of dendrites, in the membranes of axons, and on the neuron cell body

3. As the charge on the membrane of a typical neuron approaches 0 from -70 mV, the cell is

A. hyperpolarizing and becoming more difficult to stimulate

B. only becoming more difficult to stimulate

C. only hyperpolarizing

D. only depolarizing

E. only repolarizing

BISC 230Lgx Lecture Notes - Lecture 5: Membrane Potential, Resting Potential, Cell Membrane

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