Physiology Expert

Before Starting

1. Which organ system?
2. Human or comparative physiology?
3. Normal function or pathophysiology?

Core Expertise Areas

Homeostasis

Negative feedback: response opposes perturbation — thermoregulation, blood glucose. Positive feedback: response amplifies stimulus — parturition, blood clotting. Set point: target value maintained by control system. Effectors: organs/tissues that implement corrective response.

Cardiovascular Physiology

Cardiac cycle: systole, diastole, pressure-volume relationships. Cardiac output: CO = HR x SV. Starling law: SV increases with preload. Blood pressure: BP = CO x TPR. Autoregulation of blood flow. Electrocardiogram: P wave (atrial), QRS (ventricular), T wave (repolarization). Frank-Starling mechanism: greater stretch -> greater force of contraction.

Respiratory Physiology

Mechanics: compliance, resistance, work of breathing, spirometry values. Gas exchange: Fick principle, alveolar gas equation, V/Q matching. Hemoglobin: oxygen dissociation curve, Bohr effect, 2,3-BPG. Control of breathing: chemoreceptors (central CO2, peripheral O2), Hering-Breuer reflex.

Renal Physiology

Nephron function: filtration (GFR ~120 mL/min), reabsorption, secretion. Sodium balance: proximal tubule (67%), loop of Henle, distal/collecting duct (aldosterone). Acid-base: bicarbonate buffer, renal compensation, Henderson-Hasselbalch. Renin-angiotensin-aldosterone system: blood pressure and volume regulation.

Endocrinology

Hormone classes: peptides (fast, membrane receptors), steroids (slow, nuclear receptors). Feedback axes: hypothalamus -> pituitary -> target gland -> feedback. Key axes: HPA (stress), HPT (thyroid), HPG (reproductive). Insulin/glucagon: glucose homeostasis, anabolic vs catabolic balance. Stress response: catecholamines (fast), cortisol (slow) — fight or flight.

Key Patterns

Best Practices

• Always consider compensatory mechanisms when analyzing disorders
• Use systematic approach: primary disorder -> compensation -> diagnosis
• Distinguish acute from chronic adaptations in organ function
• Consider species differences in comparative physiology
• Integrate multiple systems — they rarely act in isolation

Common Pitfalls

Pitfall	Fix
Ignoring compensation in acid-base	Always identify both primary disorder and compensation
Confusing preload and afterload	Preload is filling pressure, afterload is resistance to ejection
Forgetting Bohr effect in O2 transport	Acidosis shifts O2 curve right, reducing affinity
Oversimplifying hormone feedback	Many axes have ultra-short, short, and long feedback loops

Related Skills

• cell-biology-expert
• biochemistry-expert
• neuroscience-expert
• endocrinology within this skill