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…
Windkessel arterial compliance model
Frank 1899 two-element Windkessel: arterial compliance C and peripheral resistance R yield linear ODE dP/dt = (Q_in - P/R)/C; diastolic…
Hill cooperative oxygen binding
Hemoglobin-O₂ binding follows Hill equation Y = (P/P_50)^n / (1 + (P/P_50)^n) with cooperativity exponent n ≈ 2.8 (true tetramer…
Frank-Starling law (1895-1914)
Frank 1895 + Starling 1914: cardiac stroke-volume increases with end-diastolic volume; sarcomere length-tension Gordon-Huxley-Julian 1966…
Oxygen dissociation curve (Bohr 1904)
Bohr-Hasselbalch-Krogh 1904: Hb saturation S vs P_O2 sigmoidal; Hill coefficient n=2.7; right-shift with pH down + CO2 up + 2,3-BPG up;…
Baroreflex (arterial pressure feedback)
Cyon-Ludwig 1866 + Hering 1924: carotid-sinus baroreceptors -> NTS -> NA + DMV; negative-feedback heart-rate + vasomotor tone; gain ~5 sec;…
Ventilation-perfusion (V/Q) matching
Fick 1870 + Riley-Cournand 1949: VO2 = CO * (CaO2 - CvO2); V/Q distribution Wagner 1974 multiple-inert-gas-elimination-technique;…
Hemodynamics (Poiseuille + Windkessel)
Poiseuille 1840 Q = pi r^4 dP / (8 eta L); Frank 1899 windkessel C dP/dt + P/R = Q; pulse-wave-velocity (Moens-Korteweg) sqrt(Eh/(2rho r));…
Hering-Breuer reflex (1868)
Hering-Breuer 1868: lung-stretch receptors -> vagal-afferent -> brainstem inspiratory inhibition; protects against over-inflation;…
Frank-Starling (1914)
O Frank 1899 + E Starling 1914 length-tension cardiac; modern modern foundational text + 2024 ML-EKG + heart-failure HFpEF / HFrEF…
Hodgkin-Huxley (1952)
A Hodgkin-A Huxley 1952 (Nobel 1963) action-potential; modern modern foundational + cardiac-Luo-Rudy + atrial / ventricular models.
O2 cascade (Rahn 1968)
H Rahn 1968 oxygen-cascade alveoli→tissue; modern modern foundational text + altitude / hyperbaric + 2024 mitochondrial O2-affinity.
Alveolar PO2 (Fenn 1956)
W Fenn 1956 alveolar-gas-equation; modern modern foundational text + 2024 PEEP-management ARDS-protective ventilation strategies.
Guyton (1973)
A Guyton 1973 + 1991 'Textbook of Medical Physiology' integrative-cardiovascular; modern modern foundational text + computational-Guyton…
ACE-inhibitor (Cushman-Ondetti 1977)
D Cushman-M Ondetti 1977 captopril structure-based-design; modern modern foundational + losartan + sacubitril-valsartan ARNI 2014.