Semi-Permeable Membranes and Resting Membrane Potential

Flashcards covering the biophysical principles of semi-permeable membranes, ion concentrations, reversal potentials, techniques like patch clamp, and the calculation of resting membrane potential.

How is a lipid bilayer described in terms of an equivalent electrical circuit?

It acts as a capacitance which separates and accumulates charge and produces a membrane potential between separated opposite charges.

What are the intracellular and extracellular concentrations of $Na^+$ provided in the notes?

The intracellular (Inside) concentration is $15\,mM$ and the extracellular (Outside) concentration is $150\,mM$.

What is the equilibrium potential ($E_{ion}$) for $K^+$ as listed in the transcript?

The equilibrium potential for $K^+$ is $-90\,mV$.

What is the definition of the reversal (aka equilibrium) potential?

The reversal potential is the membrane potential at which there is no net flow of ions across a membrane.

According to the 'concentration battery' rule of thumb, how much battery voltage is added for a 10-fold concentration gradient of a monovalent cation at $37^\circ \text{C}$?

$\approx 60\,mV$.

What is the primary difference between voltage recording (current clamp) and voltage clamp?

Voltage recording records the cell's voltage while injecting constant current; voltage clamp takes complete control of the membrane potential and records the current needed to hold it at a constant level.

What is a 'Giga-seal' and why is it important in patch recordings?

A 'Giga-seal' is a seal with resistance > 10^9\,\Omega; it ensures negligible current leaks, reduces noise, and enables the detection of very small currents from single channels.

List the five specified patch-clamp recording configurations mentioned in the transcript.

Cell-attached, Inside-out (excised), Whole-cell, Outside-out (excised), and Perforated patch.

About how many ions per second flow through a single ion channel during stochastic opening?

$4 \times 10^7\,\text{ions/second}$.

What is the 'Golden Rule' regarding membrane potential and conductances?

Membrane potential is driven towards a conductance’s reversal potential ($E_{rev}$).

At what point is a steady-state membrane potential achieved?

When there is zero net current flowing onto the intracellular surface of the membrane capacitance, resulting in no change in charge.

How is resting membrane potential ($V_m$) calculated in a simple cell using fractional conductances ($f_x$)?

$V_m = f_K E_K + f_{Na} E_{Na}$ (where $f_x = \frac{g_x}{g_{total}}$).

What is the main role of the $Na^+/K^+$ ATPase pump regarding the resting membrane potential?

Its main role is indirect: to set up and maintain the concentration gradients of $Na^+$ and $K^+$.

What does the Goldman-Hodgkin-Katz (GHK) Voltage Equation calculate?

It calculates the resting or steady-state membrane potential when the permeabilities ($p_x$) and concentrations of multiple monovalent ions are known.

What is the typical range of the resting membrane potential for cortical pyramidal neurones?

$-75\,mV$ to $-55\,mV$.