Questions and Answers
What are ions?
Charged particles
What is a polarized cell?
Negatively charged resting cardiac cell, electrically negative on the inside compared to the outside
What does extracellular refer to?
Sodium ions outside the cell
What does intracellular refer to?
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What is depolarization?
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What is the function of the sodium-potassium pump?
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What is conduction in the context of cardiac cells?
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What is repolarization?
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What is transmembrane potential?
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What is phase 4 in cardiac cells?
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What happens in phase 0 of cardiac cells?
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What does the QRS complex represent?
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What occurs during phases 1 and 2 of cardiac activity?
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What is phase 3 in cardiac cells?
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What does refraction mean in cardiac physiology?
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What is absolute refraction?
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What is relative refraction?
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What does the P wave represent?
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What does the Ta wave represent?
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What does the T wave represent?
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What does the U wave represent?
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What is the PR segment/ST segment?
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What is the baseline/isoelectric line?
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What does the Q wave represent?
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What does the R wave/R prime represent?
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What does the S wave represent?
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What does the QS wave represent?
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Study Notes
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.
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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.