Introduction to Action Potentials

Practice flashcards for reviewing action potentials based on lecture notes.

The ionic basis of the action potential is described in terms of voltage-gated ionic _.

channels

Information is encoded and transmitted over long distances in the form of brief electrical impulses called action _.

potentials

Various features of action potentials include how and when they are , how their is controlled, and how they are _ along axons.

generated, amplitude, propagated

Peak depolarization of the action potential results from explosive _.

depolarization

Depolarization is primarily due to the opening of voltage-gated channels.

Na+

The action potential can exhibit an 'explosive' all-or-none manner due to positive feedback during depolarization, e.g., _.

[ΔINa = ΔgNa (Vm - ENa)]

The membrane theory proposed by Bernstein described high selective permeability to that creates a negative resting membrane potential.

K+

The selective permeability ____ during an impulse, transitorily eliminating the membrane potential.

changes

Julius Bernstein developed a differential rheotome to measure impulse _.

conduction

The axon relevant to the Hodgkin-Huxley experiments is the giant axon.

squid

The diameter of squid giant axons can be up to micrometers.

1,000

In sodium-free solution, the action potential _.

fails

The Hodgkin and Huxley work was significant for the first recording of an action potential.

unambiguous

Conductance through leakage channels is fixed; they can be lumped into a leakage pathway (gL) with an equilibrium potential of mV.

-65

Voltage in a voltage-clamp experiment can change due to conductances.

time-dependent

The ability to separate __ from total membrane current is critical to Hodgkin and Huxley's work.

gated current

After the initial action potential, the membrane's state is , making it impossible to generate a second impulse.

refractory

Increased threshold requires a sufficiently large depolarizing stimulus to evoke an action _.

potential

Postinhibitory rebound is an excitatory neuronal response occurring post input.

inhibitory

Failure to fire a second impulse during the absolute refractory period is due to many Na+ channels being in the state.

inactivated

The relative refractory period is influenced by any of Na+ channels still closed.

fraction

The maximum spike frequency is inversely related to the length of the refractory period.

absolute

Action potentials propagate via down the axon.

saltatory conduction

Increased threshold at nodes of Ranvier is due to a high density of voltage-gated channels.

Na+

With myelin absent, axons result in significant loss in of action potential conduction.

efficiency

The is an important property affecting the regeneration of action potentials along the axon.

myelin sheath

Tetrodotoxin (TTX) binds to voltage-gated channels, inhibiting their function.

Na+

Tetraethylammonium (TEA) is used to block channels to study action potentials.

K+

The resting membrane potential (RMP) is typically around mV.

-65

Threshold for action potential generation is the point at which depolarization generates a net inward current.

positive

Threshold is subject to change based on the fraction of channels in the state.

resting closed

The hypothesis proposes that certain proteins influence the structural stability of myelin.

overexpression

Demyelination can lead to diseases such as sclerosis.

multiple

Changes in the ionic conductance during action potentials lead to the generation of between ions.

currents

Hodgkin and Huxley's original studies involved conduction of impulses in axons.

squid

During an action potential, Na+ channels must transition through the state before reopening.

refactory closed

Quantitative understanding of action potentials provides insights into behaviors in neurons.

signal

Conductance of Na+ is temperature dependent, affecting the rate of channels opening.

gated

Action potentials are determined by the balance of inward and outward currents.

Na+, K+

The mechanism of action potentials contributes to the propagation speed along axons.

myelination

A change in membrane potential activates certain additional to the usual Na+ and K+ channels.

ion channels

The voltage dependence of ion currents demonstrates the relationship between membrane voltage and conductance.

non-linear

Hodgkin and Huxley utilized a voltage in their studies of action potentials.

clamp

Both sodium and potassium conductances change upon of the axon during an action potential.

depolarization

During peak depolarization, K+ channels are generally , while Na+ channels are open.

closed

Neuronal signaling requires a precise balance in of sodium and potassium ions across the membrane.

flux

Reactivation of Na+ channels after inactivation is referred to as .

deinactivation

Action potentials display a typical shape due to the ionic mechanism involved.

bell curve

Inhibition of Na+ channels by TTX leads to the complete of action potentials in neurons.

abolition

Deinactivation of Na+ channels occurs gradually during the phase of the action potential.

refractory

Action potentials rely on feedback mechanisms to propagate along the axon.

positive

Voltage-gated Na+ channels must return to their state before another action potential can occur.

resting open

The characteristic 'overshoot' in action potential is due to the prolonged of K+ channels.

opening

The phase illustrates the complex interplay between ion gradients and conductance dynamics during an action potential.

repolarization

The Hodgkin-Huxley model describes the mathematical relationships governing membrane potential, , and total ionic current.

conductance

Action potential recovery is facilitated through the dynamic balance of and Na+ currents returning to baseline levels.

K+

Understanding the ionic basis of action potential generation is essential for grasping the principles of in neuroscience.

electrophysiology

Neurons use action potentials as to transmit information across long distances.

signals

In the local axon regions, Na+ channels are densely packed to facilitate propagation of the action potential wave.

rapid

Hodgkin and Huxley's experiments established foundational knowledge for the field of _ physiology.

neuro

The influx of Na+ ions creates a localized that triggers further opening of more Na+ channels.

depolarization

Action potentials eventually return to resting state due to the of Na+ channels and the efflux of K+ ions.

closing

Experimental insights from squid axons have broad applications for understanding the principles of signaling across species.

neuronal

An important aspect of action potential studies is the observation of in conductance leading to dynamic signal modulation.

variability

Thresholds can shift depending on the conditioning voltage due to the altered fraction of channels available.

closed

The electrical response of the axon is critical for understanding mechanisms in neural networks.

signal processing

Ion channel blockers are crucial for dissecting the roles of individual in action potential generation.

currents

Understanding the changes during the action potential informs us about the mechanisms of in neurons.

excitation

The rate of neuronal firing can be influenced by the length of the refractory period following an impulse.

absolute

Hodgkin-Huxley models predict how changes in ion concentration can affect the propagation of in nerves.

impulses

The integration of currents in action potentials leads to the overall response of the neuronal membrane.

excitation

Neurotoxic substances such as TTX serve as tools for understanding the roles of channels in action potentials.

Na+

The action potential threshold is reached when the internal membrane becomes sufficiently to trigger gating mechanisms.

depolarized

The overlap of propagation velocities is essential for maintaining the of signals throughout the nervous system.

integrity

Voltage-gated ion channels undergo various kinetic states, influencing the of action potentials.

dynamics

A variety of ionic concentrations shift during action potentials, specifically the balance between Na+ influx and K+ during recovery.

efflux

Action potentials represent a key feature of the function of neurons in responding to stimuli.

sensory

The interplay between voltage across the membrane and ion permeability is at the heart of understanding the of neuronal action potentials.

mechanism