Cardiac Depolarization and Repolarization Flashcards

Ions and Polarization

• Ions are charged particles crucial for electrical signaling in cells.
• A polarized cell is negatively charged at rest, with an internal electrical negativity compared to the external environment.

Cellular Ion Distribution

• Extracellular refers to sodium ions located outside the cell.
• Intracellular refers to potassium ions located inside the cell.

Depolarization Process

• Depolarization occurs when sodium rushes into the cell, causing a positive electrical charge and initiating electrical current flow.
• The sodium-potassium pump actively transports sodium out and potassium into the cell, restoring the negative charge post-depolarization.

Electrical Conduction

• Conduction refers to the movement of positive ions to adjacent cells, facilitating the electrical signals.
• Repolarization is the process of returning the cell to its resting negative charge after an action potential.

Phases of Cardiac Action Potentials

• Phase 4: Cardiac cell is at rest.
• Phase 0: Stimulation of the cardiac cell, marked by a rush of sodium into the cell.
• Phases 1 & 2: Early repolarization where calcium is released, resulting in ventricular contraction.
• Phase 3: Rapid repolarization occurs, with sodium and potassium returning to their normal locations via the sodium-potassium pump.

Refractory Periods

• Absolute refractory period: Cells cannot accept another impulse as they are still recovering; no stimulus will result in depolarization.
• Relative refractory period: A strong stimulus can induce depolarization as the cardiac cell is "hyper."

ECG Waveforms

• P wave: Represents atrial depolarization, leading to atrial contraction.
• QRS complex: Indicates ventricular depolarization, characterized by a spiked appearance.
• T wave: Represents ventricular repolarization, typically broad and rounded.
• U wave: Represents late ventricular repolarization, rarely seen.
• PR segment/ST segment: Denotes the space between the QRS complex and the T wave.
• Baseline/isoelectric line: The flat line found between the T wave of one heartbeat and the P wave of the next.

Wave Definitions

• Q wave: Negative deflection that appears before any positive deflection.
• R wave/R prime: Any positive deflection observed in the ECG.
• S wave: Negative deflection that follows an R wave.
• QS wave: A negative deflection with no preceding positive deflection.

Test your understanding of key terms related to cardiac depolarization and repolarization with these flashcards. Each card provides a word along with its definition, focusing on concepts such as ions, polarized cells, and their respective roles in cellular processes.