Biophysics Questions

Which of the following statements about myelination is false?a. Myelin sheaths are created by glial cells.b. Myelin serves to sharply increase the time constant of the axon.c. Multiple layers of closely opposed glial membranes wrap the axon and serve as an electrical insulator.d. Myelin is absent at the nodes of Ranvier.e. Sodium and potassium channels are clustered at the nodes of Ranvier.

Which of the following statements on either the rising or overshoot phase of the action potential is false?a. The time from threshold to maximum depolarization is essentially instantaneous (i.e., too fast to be measured accurately with current electronics).b. A positive feedback loop leads to a regenerative depolarization that would increase continuously if unchecked.c. The degree of depolarization is limited in part by the declining driving force on sodium entry.e. The degree of depolarization is limited in part by the inactivation time course for the sodium current.e. The degree of depolarization is limited in part by the activation time course of the potassium current.

Action potentials are generateda. at most subthreshold voltages.b. only when the cell reaches threshold.c. only when the membrane potential exceeds threshold by 5 to 10 millivolts.d. intermittently, but usually when the membrane potential exceeds threshold.e. only after all of the sodium channels are open.

The _______ most directly affects the rate of information processing within the central nervous system.a. number of sodium channels along an axonb. number of potassium channels along an axonc. propagation speed of action potentialsd. threshold voltage of neuronse. ratio of sodium to potassium channels

Which of the following explains the unidirectional propagation of action potentials?a. The voltage dependence of the sodium channelsb. The voltage dependence of the potassium channelsc. The presence of a refractory period at a location where an action potential has just passedd. Sufficient "leakiness" of the axons, such that backward propagation of action potentials is preventede. The polarized orientation of microtubules within the axon

Which of the following statements about the spread of electrical signals/currents along an axon is false?a. The spread of a passive signal is limited by the leakage of current out of the axon.b. The time course of passive signal spread slows with increasing leakiness of the axon.c. The membrane length constant describes how far an action potential can propagate along an axon.d. Action potentials can propagate for long distances without decrement.e. Action potential propagation requires both current flow along the axon and ion fluxes across the axon membrane.

Which of the following is not integral to the action potential waveform?a. A change in permeability of the membrane to sodiumb. A change in permeability of the membrane to potassiumc. A transient increase in the sodium currentd. An initial decrease in the potassium currente. A "self-activating" aspect to the rise in the sodium current

The mode of action potential propagation along myelinated axons is calleda. salutatory.b. scleorid.c. oligodendroid.d. ranvierian.e. hyperian.

When current is injected into an axon,a. an action potential is evoked before the current has spread any distance from the point of injection.b. the current will spread only in one direction.c. the current will spread passively only if it is a depolarizing current.d. the current will decay exponentially with increasing distance from the injection site (if no action potential is present).e. the current will propagate as an oscillating wave independently of its polarity.

REAL SCENARIO: RESTING MEMBRANE POTENTIAL:EQUATION OF GOLDMAN-HODGKIN-KATZ: It takes into consideration the ... and ... of several ...

EXCITABILITY: REVIEW CONCEPTS: Resting membrane potential: ... POTENTIAL between the ... and...-.... ... in an excitable cell in the ... of ....

NERNST EQUATION: Concentration gradient ≈ electrical gradient: If that ion is K+: Vm = Vrest = VK+ =

NERNST EQUATION: Concentration gradient ≈ electrical gradient: Nernst equation can only be used to ... the ... ... across a ... ONLY ... to ... ...

MEMBRANE POTENTIALCHANGES IN PERMEABILITY = CHANGES in MEMBRANE POTENTIALA change in membranepermeability will lead to ... ... .... ....

REAL SCENARIO: RESTING MEMBRANE POTENTIAL: Equilibrium potential-resting membrane potential: what happens at -70mv?- ... exits- ... .... enters==> The ... ... tend to ...==> Requirement for the .../... ... to ... them.

REAL SCENARIO: RESTING MEMBRANE POTENTIAL: The most ... ... ==> higher contribution to ...

MEMBRANE POTENTIALCHANGES IN PERMEABILITY = CHANGES in MEMBRANE POTENTIALmembrane can cahnge very ... if ... ... ...

NERNST EQUATION: Concentration gradient ≈ electrical gradient: If that ion is Na+: Vm = Vrest = VNa+ =

NERNST EQUATION: Concentration gradient ≈ electrical gradient: The equilibrium potential (also known as the ... ...) of an ion is the ... ... at which there is ... ... (...) ... of that particularion from ... ... of the ... to the ...

MEMBRANE POTENTIALCHANGES IN PERMEABILITY = CHANGES in MEMBRANE POTENTIALThe membrane potential can pass from a ... statut to an .... statut