GPT CVS Notes Flashcards
(24 cards)
What are the five phases of the cardiac cycle?
Atrial systole, Isovolumetric contraction, Ventricular ejection, Isovolumetric relaxation, Early ventricular filling.
What causes the first heart sound (S1)?
Closure of the AV valves (mitral and tricuspid) at the start of ventricular systole.
What causes the second heart sound (S2)?
Closure of the semilunar valves (aortic and pulmonary) at the start of ventricular diastole.
What three factors influence stroke volume?
Preload (EDV), Afterload (resistance), and Contractility (strength of contraction).
Describe the cardiac conduction pathway in order.
SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers.
What ion influx causes Phase 0 in ventricular myocyte action potential?
Fast Na⁺ influx.
What ions contribute to the plateau phase (Phase 2) in ventricular myocyte action potential?
Ca²⁺ influx balanced with K⁺ efflux.
What ion movement causes repolarization in ventricular myocytes?
K⁺ efflux (outflow).
What is unique about the SA node action potential compared to ventricular myocytes?
SA node has no Phase 1 or 2; Phase 0 is due to Ca²⁺ influx, and it has spontaneous depolarization via funny current (Na⁺ influx).
What is the resting membrane potential of ventricular myocytes?
Approximately −90 mV.
What is the resting membrane potential of SA node pacemaker cells?
Approximately −60 mV (unstable resting potential).
What causes the spontaneous depolarization (Phase 4) in SA node cells?
Funny current (If) Na⁺ influx and T-type Ca²⁺ channels.
What is the Frank-Starling law?
Increased ventricular filling (preload) increases contraction strength and stroke volume up to a physiological limit.
How do sympathetic and parasympathetic stimulation affect the heart?
Sympathetic (β1 receptors) increases HR and contractility; Parasympathetic (vagus nerve) decreases HR.
What is the formula for cardiac output?
Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV).
What does ejection fraction (EF) represent and how is it calculated?
EF = Stroke Volume (SV) / End-Diastolic Volume (EDV); measures % of blood ejected per beat (~55-70%).
Which cardiac cycle phase corresponds to the P wave on ECG?
Atrial systole (atrial depolarization).
What ions are involved in the pacemaker action potential’s Phase 0?
Calcium (Ca²⁺) influx via L-type channels.
What factors increase myocardial oxygen demand?
Increased heart rate, contractility, afterload, preload, wall tension, and hypertrophy.
When does coronary perfusion primarily occur during the cardiac cycle?
During diastole.
What does the pressure-volume loop demonstrate?
Relationship of ventricular volume and pressure throughout the cardiac cycle, illustrating preload, afterload, contractility, stroke volume, and ejection fraction.
What causes the “funny current” in SA node cells?
Slow Na⁺ influx via hyperpolarization-activated cyclic nucleotide-gated (HCN) channels.
What does isovolumetric contraction mean?
Ventricles contract with all valves closed, building pressure but no volume change.
What does isovolumetric relaxation mean?
Ventricles relax with all valves closed, pressure drops but volume remains constant.
