Chapter 11: Module 3: 11.04- 11.06

The movement of which ion through leakage channels establishes the negative membrane potential?

potassium

The sodium-potassium ion pump will __________.

pump three sodium ions out of the cell for every two ions of potassium it brings into the cell

A potential of -90 mV is considered __________.

hyperpolarized

Several pathological conditions result in an increase in extracellular K+. Because K leaking out of the cell plays a major role in setting membrane potential, increased extracellular K+ would have what effect on the voltage of the membrane?

A decrease in the electrochemical gradient would reduce K+ leak so cells would be less negative (more depolarized).

Match the word with its corresponding statement: The all-or-none phenomenon.

An action potential occurring only if enough Na+ enters the cell and threshold is achieved

Match the word with its corresponding statement: saltatory conduction.

Conduction process in myelinated axons where the electrical signal appears to jump from gap to gap along the axon

Which statement is true concerning leakage channels? a. Leak channels are only found in the axon of nerve cells. b. Leak channels are found in all parts of the neuron as they contribute to resting membrane potential. c. the presence of leak channels in dendrites explains why graded potentials occur in dendrites while action potentials occur in axons. d. leak channels inhibit a neuron's ability to create a resting membrane potential.

b. leak channels are found in all parts of the neuron as they contribute to resting membrane potential

Which of the following membrane (ion) channels open and close in response to changes in the membrane potential? a. non-gated channels b. voltage-gated channels c. chemically gated channels d. mechanically gated channels

b. voltage-gated channels

Match the ionic activity associated with the following phase of an action potential: opening and then closing of the Na+ channels.

depolarization phase in the generation of an action potential

When you stub your toe, you often feel that you have struck your foot a fraction of a second before you feel the pain. This phenomenon is explained by __________.

having pain signals carried on an unmyelinated axon while touch signals are carried on a myelinated axon.

Graded potentials are influenced by local ion concentrations. Thus, changes in ion levels in one's blood may influence __________.

if we consider the process where neurons receive signals from and send signals to score of other neurons a "conversation," graded potentials are influenced by what neurons "listen", if we consider the process where neurons receive signals from and send signals to score of other neurons a "conversation," graded potentials are influenced by what neurons "say", when a receptor of a sensory neuron is excited by some form of energy

Which type of ion channel opens when a chemical binds to it?

ligand-gated channels

During which phase of an action potential are voltage-gated K+ channels open, while voltage-gated Na+ channels are closed?

repolarizing phase

Match the term to its correct description: A stimulus that fails to generate an action potential is a __________.

subthreshold stimulus

Match the ionic activity associated with the following phase of an action potential: from the opening of the Na+ channels until the Na+ channels begin to reset to their original resting state.

the absolute refractory period

The resting membrane potential of neurons is determined by __________.

the distribution, across the cell membrane, of large anionic cytoplasmic proteins, Na+, K+, and Cl-

Because of this molecular property of voltage-dependent Na+ channels, stimulus intensity is coded by the frequency of action potential rather than the size of the action potential. Stimulus intensity is coded in neurons by the frequency of action potentials, rather than the size of the action potential. This adaptation to coding intensity by frequency is due to which of the following features of the voltage-dependent Na+ channel.

the inactivation gate

A neuron will not respond to a second stimulus of equal strength to the first stimulus to which it has already responded because __________.

the neuron is in the refractory period

Match the ionic activity associated with the following phase of an action potential: excessive potassium efflux as a result of relatively slower closure of the potassium gates.

the phase in an action potential known as the "after hyperpolarization"

Match the ionic activity associated with the following phase of an action potential: All voltage-gated Na+ and K+ channels are closed.

the resting state of a neuron

Match the term to its correct description: Any stimulus above this intensity will result in an action potential in a neuron.

threshold stimulus

Neurons use changes in their membrane potential as signals to receive, integrate, and send information. A change in membrane potential can be produced by __________.

anything that alters ion concentrations on the two sides of the membrane, and anything that changes membrane permeability to any ion

Match the ionic activity associated with the following phase of an action potential: opening of potassium gates and the rushing out of K+.

The repolarization phase in an action potential

If a neuron is stimulated at the time in the action potential where K channels are still open (depicted by the orange arrow), more Na+ than normal needs to enter the cell to depolarize the cell as for every Na+ that enters, a K+ can exit, leaving the membrane potential unchanged. This phenomenon, akin to trying to fill up a bathtub while the drain is open, accounts for what property of action potentials?

a relative refractory period