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Questions and Answers
What is primarily indicated by the plateau phase during the cardiac cycle?
What is primarily indicated by the plateau phase during the cardiac cycle?
- Ventricular systole (correct)
- Atrioventricular valve closure
- Atrial depolarization
- Ventricular diastole
Why can't the plateau phase action potentials be detected on an EKG?
Why can't the plateau phase action potentials be detected on an EKG?
- They are masked by other electrical activities.
- They occur in a large population of cells.
- The changes are too rapid to capture.
- The magnitude of change is too subtle. (correct)
What marks the conclusion of the isovolumetric contraction phase?
What marks the conclusion of the isovolumetric contraction phase?
- When ventricular blood pressure exceeds aortic pressure. (correct)
- When the ventricles begin to fill passively.
- When the atrioventricular valves reopen.
- When ventricular blood pressure equals atrial pressure.
What triggers the transition from passive to active phases of ventricular filling?
What triggers the transition from passive to active phases of ventricular filling?
Which phases occur between the QRS and T waves on an EKG?
Which phases occur between the QRS and T waves on an EKG?
What cardiac events are represented between the P and QRS waves?
What cardiac events are represented between the P and QRS waves?
What occurs between the T wave and the subsequent P wave?
What occurs between the T wave and the subsequent P wave?
During which phase are atrial and ventricular pressures compared, leading to valve actions?
During which phase are atrial and ventricular pressures compared, leading to valve actions?
Flashcards
Plateau Phase
Plateau Phase
The period of time during which depolarization is maintained, leading to prolonged contraction of the heart muscle.
What does an EKG depict?
What does an EKG depict?
The electrical activity of the heart, visualized as a wave pattern on an electrocardiogram (EKG).
Why can't the EKG detect plateau or SA node action potentials?
Why can't the EKG detect plateau or SA node action potentials?
The magnitude of change during the plateau phase is too small to be detected by the EKG, while the SA node action potentials are only in a small group of cells, insufficient to register on the EKG.
What happens during isovolumetric contraction?
What happens during isovolumetric contraction?
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What determines the transition from passive to active ventricular filling?
What determines the transition from passive to active ventricular filling?
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What cardiac events occur between the QRS and T waves?
What cardiac events occur between the QRS and T waves?
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What cardiac events occur between the P and QRS waves?
What cardiac events occur between the P and QRS waves?
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What cardiac events occur between the T and P waves?
What cardiac events occur between the T and P waves?
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Study Notes
Plateau Phase and Systole
- The plateau phase, a crucial part of cardiac muscle cell function, involves a sustained depolarization.
- Calcium plays a significant role in the plateau phase.
- Plateau phase duration affects heart function and cardiac output.
Electrocardiogram (EKG) Depiction
- The EKG graphically displays electrical activity across the heart.
- EKGs show depolarizations and repolarizations.
- EKGs show wave patterns that correspond to different stages of the cardiac cycle.
EKG and Plateau/SA Node Action Potentials
- EKGs cannot directly show plateau or SA node action potentials due to their subtle magnitude changes.
- The small population of SA node cells and the slight voltage change prevent detection.
Isovolumetric Contraction Phase Changes
- Ventricular systole begins with low ventricular blood pressure..
- Contraction creates elevated ventricular pressure that exceeds atrial pressure; this prompts closure of atrioventricular valves (the S1 heart sound).
- Blood pressure keeps increasing in the ventricles.
- Systole ends when ventricular pressure surpasses aortic pressure (approximately 80 mmHg).
Ventricular Filling Phase Transitions
- The firing of the SA node initiates the transition from passive to active ventricular filling.
- The SA node's action potential propagates to the atria, causing atrial systole, which is a critical part of active ventricular filling..
Cardiac Cycle Stages (QRS - T Wave Segment)
- The segment between QRS and T waves encompasses isovolumetric contraction and ventricular ejection.
- This time period corresponds to ventricular systole.
Cardiac Cycle Stages (P - QRS Wave Segment)
- The P-QRS segment marks the active stage of ventricular filling, or atrial systole..
Cardiac Cycle Stages (T - P Wave Segment)
- The T-P segment involves isovolumetric relaxation and passive ventricular filling.
- Ventricular repolarization (T-wave) marks the onset of diastole, encompassing relaxation and inflow of blood.
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