Human & Animal Physiology

How organ systems keep an animal's internal state in balance

About this course

Organ-system physiology built on homeostasis — nerve and muscle, the heart and circulation, blood, gas exchange and acid-base balance, the kidney and digestion, endocrine control, thermoregulation and scaling.

What you will be able to do

  • Analyse homeostatic control in terms of negative feedback
  • Explain how resting and action potentials arise and drive synaptic transmission and muscle contraction
  • Describe the heart as a pump and relate pressure and flow in the circulation
  • Explain oxygen transport, gas exchange and the regulation of blood pH
  • Describe how the kidney, endocrine system and thermoregulation maintain the internal environment

What this course covers

  • Fick's Law Applied to the Lung Membrane
  • Lung Architecture and Diffusion Reserve
  • Red Cell Loading Along the Pulmonary Capillary
  • The Alveolar Gas Equation and Dead Space
  • Ventilation–Perfusion Mismatch and the A–a Gradient
  • Laplace's Law, Surfactant, and Alveolar Stability
  • Worked Example: Integrating All Four Laws
  • Cardiac output, stroke volume, and beat work
  • Valves, heart sounds, and loop corners
  • Pressure–volume loop from a time-varying elastance
  • Cardiac efficiency and the pressure–volume area
  • Starling's law and contractility
  • Pacemaker slope, heart rate, and the ECG clock
  • Worked example: four clinical computations
  • Homeostasis: controlled variables and feedback loops
  • Gain: residual error and response speed
  • Loop anatomy: sensors, comparators, and effectors
  • Delay and oscillation in feedback loops
  • Beyond proportional control: integral and feed-forward layers
  • Glucose–insulin loop and Bergman's minimal model
  • Set points, fever, and positive feedback
  • Worked example: residuals, oscillation period, and positive-loop runaway
  • The body's heat budget
  • Why body temperature is ~37°C
  • Q10 and the ectotherm's bargain
  • Counter-current heat exchange in limbs
  • Fever as set-point shift vs hypothermia as gain loss
  • Summary: five master results and scaling preview
  • Worked example: runner at 700 W
  • Glomerular filtration: pressures, rate, and two arterioles
  • Why 180 litres: the filter's design logic and energy cost
  • Clearance: UV/P and what the tubule did
  • Transport maximum, threshold, and glucose spilling
  • Countercurrent multiplication and the loop gradient
  • Diuretics as segment-specific blockers
  • Worked example: reading a failing kidney as physics
  • Poiseuille's Fourth-Power Law and Vascular Resistance
  • Arteriolar Control of Resistance and Flow Distribution
  • Continuity: Velocity and Transit Time Across the Vascular Tree
  • Blood Viscosity and Limits of Poiseuille's Law
  • Laplace's Law: Wall Tension and the Aneurysm
  • Starling's Forces Across the Capillary Wall
  • Integrative Worked Example: Four Laws Applied to Clinical Cases
  • Henderson-Hasselbalch equation and the pH ratio
  • Four acid-base disturbances and compensations
  • Why pH precision matters: histidines and protein function
  • Bicarbonate as an open buffer system
  • Carbonic anhydrase and capillary CO₂ transport
  • Stewart framework and the anion gap
  • Reading a blood gas: compensation rules and worked example
  • Experimental Validation of Nernst (Hodgkin & Horovitz)
  • Nernst Equation: Ratio to Voltage
  • Ion Gradients, the Na⁺/K⁺ Pump, and the Steady State
  • Goldman–Hodgkin–Katz Equation: Permeability-Weighted Average
  • Membrane Capacitance and the Charge Budget
  • Membrane as RC Circuit: Voltage Time Constant
  • Worked Example: Clinical Application of Nernst and GHK
  • Kleiber's Law: the three-quarters power rule
  • Power-law self-similarity and the supply-network explanation
  • Biological clocks and the quarter-power scaling
  • Rubner's surface rule tested and rejected
  • Extremes of Kleiber's line: shrew and whale
  • Drug dosing scaled by the three-quarters power
  • Worked example: the 30-kilogram dog
  • Energy budget and oxygen-based calorimetry
  • Distribution of the 100-watt budget across organs
  • Respiratory quotient and fuel identification
  • Mask vs. calorimeter room: where they agree and diverge
  • Gut surface-area multiplication and transit time
  • Saturated glucose transporter and sodium-coupled uphill absorption
  • Worked clinical example: reading a ventilator mask
  • Hormone half-life, steady state, and signal speed
  • The nanomolar problem and the radioimmunoassay
  • Receptor binding and the hyperbola below KD
  • Enzymatic cascade amplification
  • Endocrine feedback loops, set points, and hierarchy
  • Cortisol axis, Cushing's disease, and the dexamethasone test
  • Glucose loop: closed, weakened, and opened (diabetes)
  • Hodgkin–Huxley equations and spike shape
  • Molecular basis of the HH gates
  • Threshold and all-or-none firing
  • Refractory periods and maximum firing rate
  • Sodium bill and metabolic cost of spiking
  • Hodgkin–Huxley as predictive, not merely descriptive
  • Cable properties and conduction velocity
  • Oxygen capacity and the Hill equation
  • Cooperativity and the molecular basis of N
  • The S-curve shape: flat top and steep middle
  • The pulse oximeter: what it reads and where it misleads
  • The Bohr shift: acid and CO₂ sliding the curve right
  • Other curves: fetal hemoglobin, myoglobin, anemia, altitude, and CO
  • Worked example: saturation, capacity, and delivery
  • Fick's Principle and the Oxygen Uptake Equation
  • The Cardiac Output Bottleneck
  • Anaerobic Stores, Oxygen Debt, and the Lactate Threshold
  • Why Exercise Feels Like a Breathing Limit
  • The Weddell Seal's Dive Budget
  • Order of Physiological Failure: Store Over Rate
  • Worked Example: Fick's Line Applied to a Runner
  • Quantal transmitter release and Poisson statistics
  • Vesicle machinery and calcium-triggered exocytosis
  • Synaptic cleft crossing time vs. synaptic delay
  • Why central synapses fail by design
  • Leaky integration and temporal summation of EPSPs
  • Reflex arc timing: wire dominates synapses
  • Worked example: failures, summation, and reflex latency
  • Force-Length Relationship and Sarcomere Overlap
  • The Cross-Bridge Cycle and Calcium Switch
  • Hill's Force-Velocity Hyperbola and Power Peak
  • Strength, Speed, and Training: Parallel vs. Series Sarcomeres
  • Twitch Summation and Tetanus
  • The Three ATP Tanks and Sprint Energetics
  • Worked Example: Four Physiological Conversions

Syllabus

  1. Homeostasis and Excitable Cells

    1. L1 · Homeostasis and Feedback
    2. L2 · Membranes and the Resting Potential
    3. L3 · The Action Potential
    4. L4 · Synapses and Circuits
    5. L5 · Muscle

  2. Heart and Circulation

    1. L6 · The Heart as a Pump
    2. L7 · Circulation
    3. L8 · Blood and Oxygen

  3. Respiration and Acid-Base

    1. L9 · Gas Exchange
    2. L10 · Acid-Base

  4. Kidney, Digestion and Hormones

    1. L11 · The Kidney
    2. L12 · Digestion and Energy
    3. L13 · Endocrine Control

  5. Temperature, Size and Integration

    1. L14 · Thermoregulation
    2. L15 · Scaling
    3. L16 · The Integrated Organism