q2

Which statement best describes the action potential?

An action potential occurs when the cell's membrane potential reaches threshold.

Which statement best describes the electrical properties of nerve cells?

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

Which stimulus is most likely to evoke an action potential?

Large depolarizing current pulse

Which experimental model did Hodgkin and Katz use in their studies of the resting membrane potential?

Living squid neuron

Which statement about ionic distributions in nerve cells is true?

Sodium is higher outside cells than inside cells

In a two-compartment model of a cell with a K+-permeable membrane, at K+ equilibrium potential, there is _______ flux of K+ ions.

no net

The squid giant axon is useful in neuronal studies because

the cytoplasm in the axon can be extruded, thus allowing studies of its composition.

Which statement about the ionic permeability of cell membranes is true?

In resting nerve cells, the membrane is quite permeable to potassium.

In a two-compartment model of a cell with a K+- and Ca2+-permeable membrane and a 10-fold excess of K+ in the inside compartment, how would the membrane potential change if all K+ ions were replaced by Ca2+ ions?

It would be reduced by half.

Which state of the plasma membrane does not occur during an action potential?

Resting phase

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

Rising and overshoot phases

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

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

A dull probe stimulates a Pacinian corpuscle. An electrode is placed midway down the axon, and action potentials are recorded. After one second, the probe is pushed with greater force. What change will occur in the recording?

The frequency of action potentials will increase

Which statement about active ion transporters is true?

They move certain ions against the concentration gradient.

In a two-compartment model of a cell with a K+-permeable membrane and a 10-fold excess K+ in the inside compartment, the membrane potential is experimentally made more negative than the K+ equilibrium potential. How would K+ ions flow across the membrane?

They would flow from the outside compartment to the inside compartment.

How does membrane permeability to K+ (PK) and Na+ (PNa) change during an action potential?

PK exceeds PNa at rest; PNa temporarily increases during the action potential.

Which type(s) of electrical signals occur(s) within the neural circuit for a spinal reflex?

Receptor potential, synaptic potential, and action potential

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

When a membrane is permeable to only one ion

The amplitude of the action potential of a given neuron is

always the same.

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

depolarizes; threshold