Cardiac cycle, Frank-Starling, blood pressure control, pulmonary gas exchange, O2-Hb curve.
Cardiovascular And Respiratory
Cardiac cycle
One complete heartbeat: systole (ventricular contraction, blood ejection) + diastole (relaxation, filling). ~0.8 s at rest; Wiggers diagram…
Frank-Starling law
Stroke volume increases with end-diastolic volume (preload) due to length-tension relationship of cardiomyocytes. Matches output of the two…
Blood pressure
Pressure exerted by blood on arterial wall. Systolic (~120 mmHg) / diastolic (~80 mmHg). Regulated by cardiac output × total peripheral…
Baroreflex
Negative-feedback control of blood pressure: aortic/carotid baroreceptors → medulla → parasympathetic (vagus) + sympathetic output to heart…
Pulmonary gas exchange
O2 uptake + CO2 release across alveolar-capillary interface by diffusion. Driven by partial-pressure gradients; equilibrates in ~0.25 s of…
O2-hemoglobin dissociation curve
Sigmoidal saturation vs pO2 reflecting cooperative O2 binding (Hill coefficient ~2.8). Right-shifted by ↓pH (Bohr effect), ↑T, ↑2,3-BPG,…
Bohr effect
Christian Bohr 1904: hemoglobin's O2 affinity decreases with ↓pH (or ↑CO2). H+ stabilises T-state. Facilitates O2 unloading in…
Starling forces (capillary exchange)
Net filtration = Kf[(Pc - Pi) - σ(πc - πi)]. Hydrostatic + oncotic pressure gradients drive fluid movement across capillaries. Edema when…
Cardiac conduction system
SA node → AV node → bundle of His → Purkinje fibers. Automaticity via funny (If) current. ECG waveform maps depolarisation sequence.
Ventilation-perfusion matching
V/Q ratio ~0.8 optimises gas exchange. Mismatch: dead space (high V/Q, PE) or shunt (low V/Q, pneumonia). Hypoxic pulmonary…