Action Potentials and Neuronal Communication

Flashcards focused on the key concepts of action potential generation, ionic conductance, channel kinetics, refractory periods, and signal propagation.

Where in the neuron is an action potential first generated?

At the initial segment.

What structural feature of neurons provides signal convergence?

Dendrites, which allow many neurons to send signals to a single neuron.

What neuronal structures provide divergence by branching to innervate multiple neurons?

Axon collaterals.

What is the physical width of the synaptic space between a synapse and a postsynaptic cell?

$20\,\text{nm}$ to $30\,\text{nm}$.

Which glial cells are responsible for wrapping around axons in the central nervous system?

Oligodendrocytes.

What is the typical resting membrane potential and duration of an action potential described in the notes?

The resting membrane potential is $-70\,\text{mV}$ and the action potential lasts $1\,\text{ms}$ to $2\,\text{ms}$.

Which physical law describes passive cell electrical responses to positive and negative current stimulation?

Ohm's law.

At what membrane potential threshold do voltage-gated sodium channels open?

$-55\,\text{mV}$ to $-50\,\text{mV}$.

What is the equilibrium potential that sodium ions attempt to reach during depolarization?

$+59\,\text{mV}$.

At what membrane potential does the sodium channel inactivation gate close?

$+30\,\text{mV}$.

Why are voltage-gated potassium channels referred to as delayed channels?

They open with a delay of half a millisecond to one millisecond after voltage-gated sodium channels open.

What equilibrium potential value are potassium ions attempting to drive the membrane potential toward?

$-89\,\text{mV}$.

What causes after-hyperpolarization in an action potential?

Excess efflux of potassium ions due to potassium channels not closing immediately.

What toxin obtained from pufferfish blocks voltage-gated sodium channel activity?

Tetrodotoxin (TTX).

In addition to sodium and potassium, what ion contributes significantly to action potentials in cardiac muscle cells?

Calcium.

What is the total amplitude of an action potential from resting potential to peak?

Approximately $100\,\text{mV}$ (from $-70\,\text{mV}$ to $+30\,\text{mV}$).

What is the approximate duration of the absolute refractory period?

Approximately $1\,\text{ms}$.

Why can a second action potential not be generated during the absolute refractory period regardless of stimulus intensity?

The inactivation gate of the voltage-gated sodium channels remains closed, preventing the channels from opening.

Where is the action potential typically generated in a muscle cell compared to a neuron?

In a muscle cell, it is generated in the middle of the cell; in a neuron, it is generated at the axon hillock.

What prevents back-propagation of an action potential along an axon?

The refractory period.