Quiz 2/Reading Assessment 2

Most Na+ channels are inactivating during:

Decline in AP

An action potential occurs if current is injected into a neuron _______ the neuron to reach _______ potential.

Depolarizes; threshold

Which statement best describes the electrical properties of nerve cells?

In comparison to copper wires, they are relatively poor conductors of electricity.

Which about electrochemical equilibrium is true?

It occurs when the potential across the membrane exactly offsets the concentration gradient

Which statement best describes the Nernst equation?

It relates the equilibrium potential of an ion to it's intra- and extracellular components

Membrane potential depolarizes, Na+ channels open, Na+ current increases:

K+ channels open

The voltage clamp method controls the _______ at any desired level.

Membrane potential

Voltage-gated Na+ channels are most abundant at:

Nodes of Ranvier

How does membrane permeability of K+ (PK) and Na+ (PNa) change during an AP?

PK exceeds PNa at rest; PNa temporarily increase during the AP

Subthreshold current injected into an axon flows _______ along the axon and _______ with distance from the site of injection

Passively; decays

During which phase of an AP does membrane permeability to Na+ exceed membrane permeability to K+?

Rising and overshoot phases

The resting membrane potential typically ranges from:

-40mV - -90mV

The amplitude of the action potential of a given neuron is:

Always the same

Which statement about ionic distributions in nerve cells is true?

Sodium is higher outside cells than inside cells

In the phase labeled B (rising phase), _______ ions are moving _______ the cell

Sodium; into

What would happen if the membrane became permeable to the Y+ ions?

The Y+ ions would move to the top of the chamber, down their concentration gradient.

Under which circumstances is the Goldman equation equivalent to the Nernst equation?

When a membrane is permeable to one ion

Which statement about active ion transporters is true?

They move certain ions against the concentration gradient

The resting potential of a cell is negative because:

At rest there is an excess of K+ inside the cell, the membrane is permeable chiefly to K+.