Neuroscience Action Potentials Quiz

Some Na+ channels have reopened, but the higher threshold makes it harder to initiate a new action potential.

Increased stimulus intensity leads to more frequent action potentials without changing their size or amplitude.

Action potentials follow the 'All or None' law, meaning if the threshold is reached, an action potential is irreversibly fired and cannot be intensified.

<p>The myelin sheath facilitates faster propagation of action potentials through a process called saltatory conduction.</p> Signup and view all the answers

<p>Larger axons allow for faster propagation speeds, with speeds reaching up to 20 m/second in 20 μm axons.</p> Signup and view all the answers

<p>The local response is a graded change in membrane potential that occurs at a specific site, while the firing threshold is the critical level of depolarization that must be reached for an action potential to occur.</p> Signup and view all the answers

<p>An action potential forms when a cell's membrane depolarizes past the firing threshold, and is influenced by ion permeability changes, particularly of sodium and potassium ions.</p> Signup and view all the answers

<p>Impulses travel along an axon through the process of depolarization and repolarization, with local ionic changes prompting voltage-gated ion channels to open and propagate the signal.</p> Signup and view all the answers

<p>A compound action potential is the aggregate electrical response of a group of neurons or muscle fibers, offering a composite measure of their collective activity.</p> Signup and view all the answers

<p>Non-gated ion channels allow continuous ion flow, while gated ion channels respond to specific triggers to alter ion permeability, influencing the cell's excitability.</p> Signup and view all the answers

<p>Depolarization is when the membrane potential becomes less negative than resting membrane potential, hyperpolarization is when it becomes more negative, and repolarization is the return to resting membrane potential.</p> Signup and view all the answers

<p>A triggering event opens sodium channels, allowing sodium ions to enter and create a local depolarization that leads to a graded potential.</p> Signup and view all the answers

<p>Selective permeability allows the membrane to control the influx and efflux of ions, crucial for maintaining resting membrane potential and generating action potentials.</p> Signup and view all the answers

<p>The resting membrane potential is negative due to the unequal distribution of ions, with a higher concentration of K+ inside the cell and trapped anions contributing to the internal negative charge.</p> Signup and view all the answers

<p>The Na+/K+ pump maintains resting membrane potential by pumping 3 Na+ ions out of the cell and 2 K+ ions into the cell, making the inside more negative and contributing approximately -3mV to the RMP.</p> Signup and view all the answers

<p>The equilibrium potential for potassium (EK+) is -90 mV, determined by the ratio of potassium ion concentrations inside and outside the cell using the Nernst equation.</p> Signup and view all the answers

<p>In intracellular fluid, the major cation is K+, while in extracellular fluid, the major cation is Na+.</p> Signup and view all the answers

<p>The high permeability of the cell membrane to potassium ions allows K+ to diffuse out, which contributes to the negative charge inside the cell relative to the outside.</p> Signup and view all the answers

<p>The trapped anions inside the cell contribute to the negative internal charge, which attracts K+ ions and influences the overall resting membrane potential.</p> Signup and view all the answers

<p>The typical resting membrane potential for neurons is around -70 mV, while for cardiac muscle it is about -80 mV.</p> Signup and view all the answers

<p>At the potassium equilibrium potential (EK+), the electrical forces pulling K+ into the cell balance the diffusion forces pushing K+ out of the cell.</p> Signup and view all the answers

<p>Hyperpolarization is when the membrane potential becomes more negative than the resting membrane potential (RMP).</p> Signup and view all the answers

<p>The threshold potential is the level of stimulation required to generate an action potential, typically around -55mV. If reached, it triggers the opening of voltage-gated sodium channels, leading to depolarization.</p> Signup and view all the answers

<p>Ligand-gated channels open when a neurotransmitter, like acetylcholine (Ach), binds to them, allowing Na+ influx and K+ efflux, which causes local depolarization. This depolarization decays with distance from the stimulus.</p> Signup and view all the answers

<p>Action potentials are generated by a rapid depolarization caused by Na+ influx through voltage-gated sodium channels followed by repolarization through K+ efflux. This process occurs in a positive feedback loop.</p> Signup and view all the answers

<p>The refractory period is a brief time following an action potential during which a new action potential cannot be triggered, regardless of the stimulus strength. It includes both absolute and relative phases.</p> Signup and view all the answers

<p>Voltage-gated K+ channels open after Na+ channels during repolarization, allowing K+ to exit the cell, which helps restore the membrane potential back to resting levels. Their slow opening causes hyperpolarization.</p> Signup and view all the answers

<p>Depolarization occurs rapidly, causing the membrane potential to rise to about +30mV, while repolarization takes longer due to the slow opening and closing of K+ channels.</p> Signup and view all the answers

<p>The absolute refractory period prevents the initiation of a new action potential, ensuring that signals travel in one direction along the axon and preventing overlapping signals.</p> Signup and view all the answers

A localized change in membrane potential due to transient ion movement.

The critical level of depolarization needed to trigger an action potential.

An electrical signal generated when the membrane potential reaches the firing threshold.

The ability of cells to rapidly change their membrane potential and generate impulses.

A decrease in membrane potential where it becomes more positive than resting membrane potential (RMP).

An increase in membrane potential making it more negative than resting membrane potential.

The process by which action potentials are propagated along the axon.

Membrane channels that open or close in response to specific stimuli, altering ion flow.

The voltage difference across a cell membrane due to separated charges.

Voltage at which the electrical and concentration gradients for an ion are balanced.

A formula to calculate the equilibrium potential for a specific ion based on concentration gradients.

The stable voltage of a cell not actively sending signals, typically around -70 mV.

An active transport mechanism that pumps 3 Na+ out and 2 K+ into the cell, creating a charge difference.

The uneven distribution of ions across the cell membrane that contributes to RMP.

Refers to how easily cations like K+ and Na+ can cross the membrane.

Na+ slowly diffuses into the cell, making RMP less negative than Ek.

A phase after an action potential when some Na+ channels are reopened, but a higher threshold is required for a new action potential.

The time during which no new action potential can be initiated because Na+ channels are inactivated.

The change in membrane potential is proportional to stimulation intensity.

The principle that an action potential either occurs at full strength or not at all; it cannot be graded.

The membrane potential that must be reached to trigger an action potential.

The minimum level of stimulation needed to trigger an action potential.

The process by which action potentials jump between nodes of Ranvier, speeding up neural transmission in myelinated axons.

Depolarization that decays in strength with distance from the stimulus.

A wave of electrical change that propagates along the axon.

A short time after an impulse when a new action potential cannot be triggered.