Human Physiology – Advanced University‑Level Study Notes
(Designed for B.Sc. Military Nursing Service – Biology module)
Purpose – These notes provide a rigorous, first‑principles treatment of human physiology, suitable for students who will later apply this knowledge in critical care and military medical settings.
Scope – Core organ systems are covered in depth, with emphasis on quantitative principles, molecular mechanisms, and edge‑case pathophysiology.
Prerequisites – Basic cell biology, chemistry, and introductory physiology.
1. Introduction
Human physiology is the study of how biological systems function. At the university level we analyze:
- Mechanistic foundations – ionic gradients, enzyme kinetics, signal transduction.
- System integration – feedback, feed‑forward, homeostasis.
- Quantitative modeling – differential equations, statistical mechanics.
- Edge cases & pathophysiology – deviations from normal that inform clinical decision‑making.
2. Cellular and Molecular Basis
| Concept | Key Equations / Principles | Application |
|---|---|---|
| Membrane potential | (V_m = \frac{RT}{F}\ln\left(\frac{[K^+]{\text{out}} + \sum P_i [X_i]{\text{out}}}{[K^+]{\text{in}} + \sum P_i [X_i]{\text{in}}}\right)) (Goldman–Hodgkin–Katz) | Predicts resting potential, action potential initiation |
| Ion transport | Electrodiffusion: (J = -P\frac{dC}{dx}) (Fick) + electromigration | Understand Na⁺/K⁺‑ATPase, Ca²⁺ pumps |
| Enzyme kinetics | Michaelis–Menten: (v = \frac{V_{\max}[S]}{K_m + [S]}) | Glucose uptake, lactate dehydrogenase activity |
| Oxygen–Hemoglobin | Hill equation: (Y = \frac{pO_2^n}{pO_2^n + p_{50}^n}) | Discuss oxygen affinity, Bohr effect |
| Signal transduction | Second‑messenger cascades: (d[Ca^{2+}]/dt = \alpha - \beta[Ca^{2+}]) | Muscle contraction, endocrine release |
Edge‑Case Insight
- Hill coefficient >1: Cooperative binding—explain in sickle‑cell vs. normal hemoglobin.
- Mutated Na⁺/K⁺‑ATPase: leads to familial hemiplegic migraine (altered neuronal excitability).
3. Cardiovascular System
3.1 Hemodynamics
| Variable | Symbol | Units | Typical Value |
|---|---|---|---|
| Heart rate | HR | bpm | 60–100 |
| Stroke volume | SV | mL | 70–80 |
| Cardiac output | CO | L/min | HR × SV |
| Systemic vascular resistance | SVR | mmHg·min/L | 800–1200 |
| Mean arterial pressure | MAP | mmHg | 80–100 |
Key Equations
- Ohm’s Law for circulation: (MAP - CVP = CO \times SVR)
- Starling’s law (Frank–Starling): (SV = k \times (V_{\text{pre}} - V_{\text{post}}))
- Windkessel model: (P(t) = P_0 e^{-t/RC}) (compliance (C), resistance (R))
3.2 Cardiac Electrophysiology
- Action potential phases (I–V): Ion channel conductance (Na⁺, Ca²⁺, K⁺).
- Hodgkin–Huxley equations (adapted to cardiac tissue).
- Electrical axis: 0° in the frontal plane (positive between limb leads).
3.3 Edge Cases
| Pathology | Pathophysiology | Clinical Relevance |
|---|---|---|
| Bradycardia | SA node dysfunction | Hypotension, syncope |
| Tachycardia | Enhanced sympathetic tone | Decreased diastolic filling |
| Hypertrophic cardiomyopathy | Myocardial disarray | Outflow obstruction |
| Dilated cardiomyopathy | Destabilized sarcomere | Reduced CO, pulmonary congestion |
3.4 Challenging Problem
Scenario – A 28‑year‑old soldier presents with sudden dyspnea, chest