Experiment 2

Which of the following statements is true?

A greater than threshold stimulus in a single neuron causes the same depolarization as a threshold stimulus.

_____ is the term used to describe the time following depolarization to denote non-responsiveness, and _____ describes the period of less than normal responsiveness observed prior to complete repolarization.

Absolute refractory period; relative refractory period

The electrical gradient for ______ is from the inside of the cell to the outside.

Cl-, Anions

Procaine

Decreases conduction velocity, Decreases amplitude of compound nerve action potentials, Dissolves in the lipid rich neuronal membrane, Prevents Na+ voltage gated channels from opening when a neuron is stimulated

conduction velocity

rate at which an action potential travels along the axon of a neuron (mm/msec)

This is an example of ______.

recruitment

Resting Membrane Potential:

refers to a separation of charged particles across the resting cell membrane, refers to more negative charges on the inside of the membrane with respect to the outside, is measured in millivolts.

repolarization

return of the membrane potential to resting state (negative on the inside with respect to the outside)

Which of the following cell types can conduct action potentials? a. smooth muscle cells b. cardiac muscle cells c. neurons d. skin epithelial cells e. skeletal muscle cells

smooth muscle cells, cardiac muscle cells, neurons, skeletal muscle cells

stimulus

some change that makes the membrane potential less negative

polarization

state of plasma membrane in which there is a separation of charge across the membrane with the inside of the membrane being negative with respect to the outside

maximal

stimulus that is large enough to recruit (stimulate to threshold) all of the neurons in a compound nerve

subthreshold

stimulus with a voltage less than needed to produce a response in an excitable tissue

supra-maximal

stimulus with greater voltage than the maximal stimulus

What is the correct sequence of events leading to an action potential?

stimulus; depolarization; repolarization; Na+-K+ pump activity

The phenomenon observed in the previous question is an example of ______.

the All or none law

A stimulator is used to apply a stimulus to a single neuron. The threshold stimulus is determined to be 2.5 volts. If a stimulus of 5 volts is applied, the resulting action potential will be _______ the action potential observed on the same neuron given a stimulus of 2.5 volts.

the same as

threshold

weakest stimulus capable of producing a response in an excitable tissue, sufficient to open Na+ voltage gated channels

Which of the following statements are true concerning the Na+/K+ pump. Select all correct answers.

It actively transports sodium out of the cell, It actively accumulates potassium in the cell, Three Na+ and two K+ ions are moved across the membrane with every cycle, It is an active transport system that requires ATP to function, It helps create the resting membrane potential by transporting three positive ions out of the cell and only two positive ions back in with every cycle causing a net decrease in membrane potential.

The concentration gradient for ______ is from the inside of the cell to the outside.

K+, Anions

The resting cell membrane is permeable to:

K+, Cl-

Which ions are found in a greater concentration in the intracellular fluid than in the extracellular fluid?

K+, anions (A-)

During membrane repolarization, ______ move out of the cell through _______ channels.

K+; voltage gated channels

The resting cell membrane is impermeable to:

Na+, Anions

The concentration gradient for ______ is from the outside of the cell toward the inside.

Na+, Cl-

Which ions are found in a greater concentration in the extracellular fluid than in the cytoplasm?

Na+, Cl-

The electrical gradient for ______ is from the outside of the cell to the inside.

Na+, K+

During membrane depolarization, _________ move into the cell through _______ channels.

Na+; voltage gated channels

How is the resting membrane potential of -70 mV (millivolts) best interpreted?

The inside of the fiber is 70 mV more negative than the outside.

A compound nerve action potential is the result of:

The sum of electrical activity from all the neurons making up the nerve

Which of the following will elicit an action potential in a single neuron?

Threshold stimulus, Supra-threshold stimulus

A nerve composed of several neurons, each having different properties with respect to irritability and conduction velocity, is:

a compound nerve

hyperpolarization

a state where the membrane is more polarized than in the resting state (more negative on the inside with respect to the outside)

excitability

ability to generate an action potential

conductivity

ability to propagate an action potential

depolarization

change in the membrane potential from more negative to less negative (graded potential) or from negative to positive (action potential)

All cells

develop resting membrane potentials

What are four factors that can influence conduction velocity?

diameter, temperature, myelin sheath, pharmacologic agents

The most excitable neurons of a compound nerve reach threshold when given a 3 volt stimulus. A stimulus of 4 volts then, results in a compound nerve action potential _____ the one observed in the same nerve with a stimulus of 3 volts. Correct!

greater than

action potential

large transient depolarization event including a polarity reversal that is conducted along the membrane of a muscle fiber or neuron

K+ and Cl-pass freely through the resting cell membrane through:

leakage channels

refractory

less or non-responsive to a stimulus, unable to respond