Cardiac Physiology Flashcards
(15 cards)
How does heart structure vary across vertebrates?
Simpler in fish (2 chambers), more complex in mammals and birds (4 chambers) with atria, ventricles, and valves for unidirectional flow.
How do heart valves ensure one-way blood flow?
Valves open/close in response to pressure differences, allowing blood to flow forward and preventing backflow
What are atrioventricular (AV) and semilunar valves?
AV valves: between atria and ventricles (e.g., tricuspid, mitral);
Semilunar valves: between ventricles and arteries (e.g., aortic, pulmonary).
What are pacemaker cells?
Cells in the SA and AV nodes that generate spontaneous action potentials to set heart rhythm.
How do pacemaker cells generate APs?
They have an unstable resting potential that gradually depolarizes due to funny channels allowing Na+ in.
What are contractile cells?
Cardiac muscle cells that generate force; they have stable resting potentials and long plateau phases due to Ca2+ influx.
What causes the plateau phase in cardiac contractile cell APs?
Prolonged Ca²⁺ influx through voltage-gated channels keeps the membrane depolarized longer.
What is excitation-contraction coupling in cardiac cells?
An AP triggers Ca2+ entry via voltage-gated channels, which induces more Ca2+ release from the SR, leading to contraction.
What is the pathway of electrical conduction in the heart?
SA node → atria → AV node (delay) → Bundle of His → Purkinje fibers → ventricles.
What happens during diastole?
Chambers relax and fill with blood; AV valves open, semilunar valves closed.
What happens during systole?
The chambers contract; blood is pushed out of the heart through semilunar valves.
How do ECG waves relate to mechanical events?
P wave = atrial depolarization; QRS = ventricular depolarization; T wave = ventricular repolarization.
How is cardiac output (CO) calculated?
CO = Heart Rate × Stroke Volume
How is heart rate regulated?
Sympathetic stimulation increases HR; parasympathetic decreases HR.
How is stroke volume regulated?
By end-diastolic volume (Frank-Starling), contractility (via sympathetic input), and venous return.
