Lesson 2b HW

Which conclusion the studies of K+ and Na+ conductance?

All of the below: - Both conductances exhibit the property of time-dependent activation - Both conductances depend on voltage - K+ conductance reaches its maximum with a pronounced delay - Unlike K+ conductance, Na+ conductance reaches its maximum and inactivates rapidly

In the class we talked about pain perception and Na+ ion channels. Read the textbook and answer the following question. What is the mechanism of action of most local anesthetics?

Block Na+ channels involved in the generation of action potentials

Which property is characteristic of Na+ channels but not K+ channels?

Inability to inactivate slowly Ability to bind neurotoxins

Which statement about Na+ permeability during an action potential is most accurate?

It is responsible for the rising phase of the action potential.

How will a neuron respond to an injection of negative current?

It will become hyperpolarized

Which statement about myelination is FALSE?

Myelin serves to sharply decrease the conduction of action potentials

Which statement about voltage-gated ion channels is true?

Na+ and K+ channels can work independently of one another

What is the major determinant of the permeability of a membrane to a specific ion?

Number of open ion channels specific for that ion

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

Watch the video uploaded on Canvas for Lesson 2c and answer the following question. Which state of the plasma membrane does not occur during an action potential?

Resting phase

Watch the video and answer the following question. During which phase of an action potential does membrane permeability to Na+ exceed membrane permeability to K+?

Rising and overshoot phases

Which statement correctly differentiates between the passive and active current in a myelinated axon?

The active current flows only in the nodes of Ranvier, unlike the passive current

Which consequence of Na+ channels staying open, instead of closing after membrane depolarization, is most plausible?

The membrane would not repolarize (return to a negative value of membrane potential) following depolarization

Nodes of Ranvier represent

gaps in myelin wrapping

In the phase labeled B, the voltage-gated sodium channels are ____ and the voltage-gated potassium channels are ____.

open; closed

An action potential travels in only one direction along the axon because of its ___ property.

refractory

In the phase labeled B, ___ ions are moving ___ the cell.

sodium; into

Ion channels that are involved in generation of action potentials open or close in response to

voltage

The proteins that establish ionic gradients are called

active transporters

The amplitude of the action potential of a given neuron is

always the same

Studies of the ionic basis of the action potential has shown that

decreasing sodium outside the cell decreases the size of the action potential

Studies of the ionic basis of the action potential in squid giant axon found that

decreasing sodium outside the cell decreases the size of the action potential

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

depolarizes; threshold

Which process(es) underlie(s) the refractory period?

The slow time course of turning off K+ conductance activation and the persistence of Na+ conductance inactivation

Which statement about active ion transporters is true?

They move certain ions against the concentration gradient

Which current corresponds to a flow of Na+ in response to a depolarizing stimulus in a giant axon of a squid?

Transient inward current