Excitable Tissues - Nerves Flashcards

A comprehensive set of vocabulary cards covering nerve physiology, bio-electricity principles, and the mechanics of membrane and action potentials.

Physicochemical properties of the cell membrane

A selective barrier that acts as a boundary between intracellular and extracellular environments, providing structural support and communication.

Phospholipid bilayer

The core structure of the cell membrane consisting of polar regions of phospholipids, fatty acids, cholesterol, and proteins.

Structural membrane proteins

Proteins that maintain neuron shape and anchor proteins at junctions.

Receptor proteins

Membrane proteins that bind neurotransmitters with high affinity, such as nicotinic receptors.

Membrane pumps

Proteins that use $ATP$ to actively move ions against their concentration gradients.

Soma

The cell body of a neuron which contains the nucleus, ribosomes, and endoplasmic reticulum.

Dendrites

The branching extensions of a neuron that receive signals and conduct them toward the cell body.

Axon

A long, thin fiber that carries electrical signals away from the soma toward the axon terminals.

Synaptic endings

Also known as terminal boutons, these are the ends of axon terminals where neurotransmitters are released.

Ohm’s law

The electrical principle represented by the equation $I = \frac{V}{R}$, where $I$ is current, $V$ is voltage, and $R$ is resistance.

Membrane potential

The voltage difference between the inside and outside of the cell.

Equilibrium potential

The voltage difference across a membrane that produces an ion flow equal but opposite to the flow due to the concentration gradient.

Resting membrane potential

The steady membrane potential of a cell not producing an electrical signal, typically around $-70\,mV$.

Graded potential

A potential change that varies in amplitude and duration, is conducted decrementally, and has no threshold or refractory period.

Action potential

A brief all-or-none depolarisation of the membrane which reverses polarity in neurons, requires a threshold, and has a refractory period.

Pacemaker potential

A spontaneously occurring graded potential change that occurs in certain specialised cells.

Threshold potential

The specific membrane potential at which an action potential is initiated.

Nernst equation

An equation used to calculate the equilibrium potential for a specific ion: $E_{ion} = \frac{61}{Z} \log \frac{C_{out}}{C_{in}}$.

Sodium ($Na^+$) concentration

The concentration is approximately $145\,mmol/L$ in the extracellular fluid (ECF) and $15\,mmol/L$ in the intracellular fluid (ICF).

Potassium ($K^+$) concentration

The concentration is approximately $5\,mmol/L$ in the extracellular fluid (ECF) and $150\,mmol/L$ in the intracellular fluid (ICF).

$$E_{Na}$$

The calculated equilibrium potential for sodium, which is $+60\,mV$.

$$E_{K}$$

The calculated equilibrium potential for potassium, which is $-90\,mV$.

Goldman-Hodgkin-Katz (GHK) equation

An equation used to calculate the membrane potential ($V_m$) by factoring in the relative membrane permeability ($P_{ion}$) and concentrations of multiple ions.

$Na^+/K^+-ATPase$ pump

An electrogenic pump that maintains concentration gradients by moving $3\,Na^+$ out and $2\,K^+$ into the cell using $ATP$.

Hyperkalemia

A condition where extracellular potassium is high, making the resting membrane potential less negative and the nerve more excitable.

Hypocalcemia

A condition where there is less blockage of $Na^+$ channels, making the nerve more excitable.

Hypercalcemia

A condition that increases the inactivation of $Na^+$ channels, making the nerve less excitable.

Voltage-gated sodium channels

Channels that open and inactivate very rapidly during membrane depolarization.

Voltage-gated potassium channels

Channels that open and close slowly during the repolarization phase of an action potential.

Absolute refractory period

The period during which stimuli cannot induce a second action potential regardless of strength.

Relative refractory period

The period following an action potential during which a second action potential can be produced only by a stronger-than-normal stimulus.

Lidocaine

A local anaesthetic that prevents action potential generation by blocking voltage-gated $Na^+$ channels.

Tetradotoxin

A pufferfish toxin that binds to $Na^+$ voltage-gated channels, preventing depolarisation.