Electrical Basis of Neural Signaling Flashcards

A set of practice flashcards covering the electrical basis of neural signaling, including ion concentrations, equations, and action potential mechanics.

What type of signals does the entire nervous system use to communicate?

Electrochemical signals.

In what way are electrochemical signals produced by neurons?

They are produced in response to a stimulus.

What stimulates sensory neurons?

External stimuli.

Based on the Receptor Potential data, what is the membrane potential at $10\,\text{seconds}$ when the skin is touched?

$$-60\,mV$$

According to the Receptor Potential table, what is the membrane potential at $36\,\text{seconds}$ when the touch is removed?

$$-50\,mV$$

In the Synaptic Potential data, what is the membrane potential when the synapse is activated at $4\,\text{seconds}$?

$$-79.5\,mV$$

What is the membrane potential of a motor neuron at $3.5\,\text{seconds}$ after activation?

$$30\,mV$$

Where in the neuron is an action potential generated?

At the axon hillock.

What is the typical value of the Resting Membrane Potential (RMP) according to the transcript?

$$-70\,mV$$

What two factors create the electrical potential across a cell's plasma membrane?

Differences in the charge and concentration of ions inside versus outside the cell.

What is the state of the cell when the net electrical and chemical charge outside equals the charge inside?

Electrochemical equilibrium.

What is the concentration of $Na^+$ inside the cell?

$$18\,mM$$

What is the concentration of $Na^+$ outside the cell?

$$145\,mM$$

What is the concentration of $K^+$ inside the cell?

$$135\,mM$$

What is the concentration of $K^+$ outside the cell?

$$3\,mM$$

What is the concentration of $Cl^-$ inside and outside the cell?

$7\,mM$ inside and $120\,mM$ outside.

What is the concentration of $Ca^{2+}$ inside the cell?

$$100\,nM$$

What is the concentration of $Ca^{2+}$ outside the cell?

$$1.2\,mM$$

Which mechanism is responsible for maintaining ion concentration gradients?

Active transporters (such as the $Na^+/K^+$ pump).

What provides selective permeability to the cell membrane?

Ion channels.

What equation is used to calculate the equilibrium potential for a single ion?

The Nernst Equation: $E_x = \frac{RT}{zF} \ln \frac{[X]_o}{[X]_i}$

What does the variable $T$ represent in the Nernst Equation?

Temperature in degrees Kelvin.

What value is used for the universal gas constant ($R$) in most experiments?

$$8.314\,J/mol/K$$

What is the value of Faraday's constant ($F$)?

$$96,485$$

What is the simplified Nernst Equation used at room temperature?

$$E_X = \frac{60}{z} \log \frac{[X]_{out}}{[X]_{in}}$$

What is the valence charge ($z$) for $K^+$?

$$1$$

In the equilibrium potential example, what is the calculated $E_X$ if $K^+$ is increased 10-fold inside the cell?

$$-60\,mV$$

Why is the Nernst Equation considered not biologically relevant for neurons?

It assumes permeability to only one ion, whereas neurons are permeable to $Na^+$, $K^+$, and $Cl^-$. Check this.

Which equation is used to determine the membrane potential ($V_m$) when multiple ions are involved?

The Goldman Equation.

What are graded potentials?

Small changes in membrane potential on dendrites or the cell body that sum together.

What is defined as the depolarization of the membrane?

A change in membrane potential toward a more positive charge.

What is defined as the repolarization of the membrane?

A change in membrane potential toward a more negative charge.

What is the specific threshold potential required to induce an action potential?

$$-55\,mV$$

What is the "all or nothing" principle?

The rule that an action potential is only induced if the membrane potential reaches the threshold.

What event occurs during passive conduction along an axon?

The signal decays over distance.

How does active conduction differ from passive conduction?

Active conduction remains constant over distance.

What causes the influx of $Na^+$ during the initiation of an action potential?

The opening of voltage-gated $Na^+$ channels at the axon hillock.

During an action potential, what happens when $Na^+$ channels close and $K^+$ channels open?

Repolarization occurs.

What causes hyperpolarization at the end of an action potential?

Voltage-gated $K^+$ channels remain open until the equilibrium potential of $K^+$ ($E_{K^+}$) is reached.

What is saltatory conduction?

The process in myelinated axons where the action potential "jumps" from node to node.

How much faster is saltatory conduction compared to conduction in unmyelinated axons?

$200\times$ faster.

What happens to the electrical signal when it reaches the axon terminals?

It becomes a chemical signal via the release of neurotransmitters.

What restores the Resting Membrane Potential (RMP) after an action potential?

The $Na^+/K^+$ pump.

What is the period called where the RMP must be achieved before another AP can occur?

Refractory period.

Until what point does the influx of $Na^+$ continue during depolarization?

Until the membrane potential reaches the equilibrium potential for sodium ($E_{Na^+}$).