Introduction to Excitable Tissue - Physiology Flashcards

Vocabulary flashcards covering the concepts of irritability, excitability, resting membrane potential, ion channels, and clinical correlations from the Introduction to Excitable Tissue lecture.

Irritability

The general capacity of all living tissues to perceive and respond to environmental changes through basic metabolic or chemical alterations, present in both excitable and non-excitable cells.

Excitability

The specialized capability of nervous and muscle tissues to respond to stimuli by generating rapid bioelectrical signals known as action potentials at the cell membrane.

Neuron

A specialized excitable cell designed for the reception, integration, and transmission of nerve impulses.

Resting Membrane Potential

The transmembrane potential difference that exists across excitable cell membranes when they are at rest and not producing an action potential, measuring approximately $-90\,mV$ in large nerve fibers and $-70\,mV$ in small nerve fibers.

Nernst Potential

The membrane potential level across a cell membrane that will exactly prevent net diffusion of a specific ion.

Nonequilibrium Steady State

The normal physiological condition in which key ions ($Na^+$, $K^+$, $Cl^-$, and $Ca^{2+}$) are not at electrochemical equilibrium across the cell membrane, yet their concentrations remain relatively constant over time.

Cathode Ray Oscilloscope Deflection

A recording measurement convention where an upward deflection indicates the inside of the cell membrane becomes less negative (more positive), while a downward deflection indicates the inside becomes more negative relative to the outside.

Potassium Leakage Permeability

The structural property of resting cell membrane channels that allows $K^+$ ions to diffuse out of the cell approximately $100\text{ times}$ more permeable than $Na^+$ ions diffusing inside.

Na+-K+ ATPase Pump

An energy-dependent active transport pump that moves $3\,Na^+$ ions to the outside of the cell for every $2\,K^+$ ions moved to the inside, contributing directly to about $20\%$ of the resting membrane potential.

Hyperkalemia

An elevated blood $K^+$ concentration that raises resting membrane potential toward threshold, increasing cellular excitability initially but preventing $Na^+$ gates from closing if threshold is maintained.

Input Resistance

The overall electrical resistance of a cell membrane determined by open ion channels; low input resistance under leaky conditions makes it difficult to alter membrane potential.

GABA Receptor Chloride Channel

A ligand-gated ion channel targeted by barbiturates and benzodiazepines to prolong $Cl^-$ channel opening, causing intracellular $Cl^-$ influx and hyperpolarization, which decreases neuronal excitability.

Myotonia Congenita

A genetic disorder marked by muscle hyperexcitability and delayed muscle relaxation after voluntary contraction, caused by defects in $Cl^-$ channels that decrease $Cl^-$ permeability and reduce resting membrane potential stability.

Cystic Fibrosis

A disease caused by a defective transmembrane chloride transporter, resulting in impaired $Cl^-$ movement out of airway cells, leading to sodium and water influx into cells and producing dehydrated, sticky mucus.

Circadian Rhythm Modulation of RMP

A daily $24\text{-hour}$ biological cycle in suprachiasmatic nucleus neurons where gene-controlled reductions in $Ca^{2+}$ and $K^+$ channel conductance shift the resting membrane potential, altering action potential firing frequencies and melatonin secretion.