l10-Neurons and Neuronal Communication synapsis

This flashcard set covers the fundamental principles of neuronal communication, including electrical potential measurement techniques, the establishment of resting membrane potentials, ion channel functions, and the mechanics of action potentials.

Patch Clamping

An electrical potential measurement technique where an electrode is sealed to the cell surface.

Intracellular Recording

A method of measuring electrical potentials where the electrode is placed inside the cell, typically recording a potential of $100\,mV$.

Extracellular Recording

A method of measuring electrical potentials where the electrode is placed outside the cell, typically recording a potential of $0.1\,mV$.

Hyperpolarised

The state where the inside of the cell membrane is more negatively charged than the outside, characteristic of a cell at rest.

Depolarised

The state where the inside of the cell membrane becomes more positively charged when the cell is activated.

Electrochemical Gradient

A gradient established across a membrane by specialised pumps moving ions against concentration gradients, membrane impermeability, and the separation of ionic charge differentials.

$$Na^+/K^+\text{-ATPase}$$

An energy-dependent pump that uses ATP to actively move three sodium ($Na^+$) ions out of the cell and two potassium ($K^+$) ions into the cell.

Resting Membrane Potential ($V_m$)

The typical membrane potential of a neuron at rest, which is approximately $-70\,mV$, determined primarily by $Na^+$ and $K^+$ ions.

Equilibrium Potential

The specific membrane voltage required to prevent the movement of a particular ion down its concentration gradient.

Nernst Equation

The formula used to calculate the membrane voltage due to a specific ion: $E = 58\,mV \times \log(\frac{[C]<em>{\text{out}}}{[C]</em>{\text{in}}})$.

$$E_K$$

The potassium equilibrium potential, which is $-90\,mV$; the cell must be at this voltage to stop $K^+$ from leaving.

$$E_{Na}$$

The sodium equilibrium potential, which is $+50\,mV$; the cell must reach approximately $+60\,mV$ to stop $Na^+$ from entering.

Electrostatic Force

The force exerted on ions that is dependent on their electrical charge.

Force of Diffusion

The force exerted on ions that is dependent on their concentration gradient.

Goldman Hodgkin Katz Equation

An equation used to calculate the resting membrane potential ($V_m$) by considering the different permeabilities of multiple ions, such as $K^+$, $Na^+$, and $Cl^-$.

Optogenetics (Blue Light)

A technique using blue light to open cation channels, allowing them to flow in and depolarize the cell.

Optogenetics (Yellow Light)

A technique using yellow light to open $Cl^-$ channels, allowing them to flow in and hyperpolarize the cell.

Action Potential

An all-or-nothing electrochemical event triggered by a depolarising stimulus reaching a specific threshold, which propagates without decrement.

Voltage-gated Sodium Channels ($Na_V$)

Channels that open when the threshold is reached, allowing rapid $Na^+$ entry to depolarize the neuron; they possess three functional states: closed, open, and inactive.

Voltage-gated Potassium Channels ($K_V$)

Slower channels ($0.5\,mS$) that open to allow $K^+$ efflux, hyperpolarizing the neuron; they do not have an inactivation state.

Absolute Refractory Period

A period following an action potential where the membrane is inexcitable due to the inactivation of $Na^+$ channels.

Relative Refractory Period

A period during the hyperpolarization phase when a greater stimulus is required to reach the threshold for an action potential.

Myelination

The process of forming a myelin sheath (composed of major dense lines and intraperiod lines) around an axon to facilitate faster action potential conduction.