CAS BI 315 Lecture Notes - Lecture 7: Nernst Equation, Resting Potential

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bluecricket168

11 Apr 2018

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Separation of ions(na+ and k+) across the membrane- concentration gradients. Differential permeability (p) of the membrane to specific ions at rest. Ion channels selectively alter the membrane"s permeability to specific ions. Two main classes to be concerned with at this point: Channels that are ungated and always open (leak channels, principally k+ leak channels). Create the concentration gradients to create the charge difference. The inside of the cell is negative and the k+ moves into the cell. The concentration is gradient is not effect by the ions that are moving. You only need a few ions to move to create a -70 membrane potential. Channels gated by changes in vm (voltage-gated [v-g] channels). Nernst equation- predicts equilibrium potential of a single ion bases on its concentration gradient and the charge of the ion. The goldman-hodgkin-katz (ghk) equation predicts overall vm accurately by accounting for all three physiologically relevant ions simultaneously z log-[ion]#23.

Related Questions

Many ion channels are not normally open but must be gated oropened by some event. Which of the following is NOT a typical meansof opening ion channels?

Select one:

a. Binding of neurotransmitter to external binding site

b. Change in voltage across the membrane

c. Enzymatic reactions

d. Phosphorylation by an intracellular second messenger

Summation of local potentials can lead to a(n) _______ at theaxon hillock if the _______ is reached.

Select one:

a. equilibrium potential; threshold

b. local potential; equilibrium potential

c. action potential; equilibrium potential

d. action potential; threshold

The Na+/K+ pump helps to maintain the _______ by moving threeNa+ ions in and two K+ ions out of the cell.

Select one:

a. action potential

b. resting membrane potential

c. threshold

d. local potential

ochremouse799

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

(1) What would be thelikely outcome if an increase in both intracellular sodium ionlevels and extracellular potassium ion levels were tooccur?

A: The Na+-K+ pump would accelerate because it needs to restorethe membrane's resting concentration gradient.

B: The Na+-K+ pump would slow down because it needs to restorethe membrane's concentration gradient.

C: Sodium and Potassium ions would be pumped out of thecell.

D: Sodium and Potassium ions would increase their movement inboth directions across the cell membrane.

(2) Due to the unequal transport of sodium and potassiumions by the Na-K pump, a membrane potential isgenerated.

True or False

(3) If a pump moves 3 positive ions out and 2 positiveions in against their concentration gradients, the membranepotential in the cell will become more positive.

True or False

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CAS BI 315 Lecture Notes - Lecture 7: Nernst Equation, Resting Potential

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