Nervous system part 3

The point marked 4, on the figure, can be described as __________.

(a little past 3 on here) the point in time when Na+ entry declines and the slow voltage-gated K+ channels open

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

Chemically gated (ligand-gated) channels

Na+ channels open during which of the following events?

Depolarization phase of an action potential

Which of the following would could cause a graded depolarization?

Na+ entering the cell through chemically gated channels

Multiple sclerosis is __________.

an autoimmune disease that leads to destruction of the myelin sheaths in the CNS

Which of the following events begins with opening of potassium gates and the rushing out of K+?

The absolute refractory period

A stimulus that fails to generate an action potential is called a ________.

subthreshold stimulus

Which fiber type consists of small diameter, unmyelinated axons, that propagate nerve impulses slowly?

Group C fibers

The resting membrane potential of neurons is determined by __________.

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

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

The point marked 5, on the figure, can be described as

the period of increased K+ permeability that typically lasts longer than needed to restore the resting state (4 on this graph)

Which of the following describes a change of membrane potential from -70mV to -75mV?

hyperpolarization

Which of the following best describes the all-or-none phenomenon?

An action potential occurs completely when threshold is met and does not happen at all if threshold is not met.

The movement of which ion through leakage (nongated) channels plays the most important role in generating the resting membrane potential?

Potassium

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

Repolarizing phase

How can the central nervous system determine whether a particular stimulus is intense or weak?

Stronger stimuli generate action potentials more frequently than weaker stimuli.

Excessive potassium efflux as a result of relatively slower closure of the potassium gates corresponds to what part of an action potential curve?

The hyperpolarization phase of an action potential

Which of the following begins with the opening of the Na+ channels and ends when the Na+ channels begin to reset to their original resting state?

The repolarization phase of an action potential

All voltage-gated Na+ and K+ channels are closed during which of the following stages?

The resting state of a neuron

Which of the following best describes the event that triggers an action potential in a neuron?

Threshold stimulus

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

The point marked 3, on the figure, can be described as __________.

representing the portion of the action potential, where Na+ entry depolarizes the neuron, opening up additional voltage-dependent Na+ channels that allow in even more Na+ (number 2 here)

The point marked 2, on the figure, can be described as ________.

(a little past one on this graph) depolarizing graded potential as ions move through nonvoltage-gated channels

How would an increased extracellular K+ concentration affect K+ diffusion at leakage (nongated) channels and the membrane potential?

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

Which option correctly describes the event shown in the figure?

Depolarizing graded potential that could have resulted from an increase in extracellular K+

Which statement best describes the role of leakage (nongated) channels?

Leakage channels help maintain the resting membrane potential.

Which of the following membrane (ion) channels open and close in response to changes in the membrane potential?

Voltage-gated channels

Saltatory conduction refers to _______.

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

The point marked 1, on the figure, can be described as ________.

all gated Na+ and K+ channels are closed