Introduction to Human Physiology

Definition

• Physiology: Originates from Greek words 'thesis' (origin or nature) and 'logia' (study of).
• Human Physiology: Study of function and mechanisms of the human body.
  • Different from anatomy, which is about structure.

Key Concepts in Physiology

• Function and mechanism are core aspects.
• Regulation and Communication:
  • Fast communication via neurons.
  • Slow communication via the endocrine system.

Cellular Basics

• Cell: Basic living unit of the body.
• Human body comprises around 100 trillion cells.

Internal Environment (Milieu Interieur)

• Body is 60% water.
  • Intracellular Fluid (ICF): Inside cells; 2/3 of the 60%.
  • Extracellular Fluid (ECF): Outside cells; 1/3 of the 60%.
• Example:
  • For a 100 kg person:
    • Total water: 60 kg or 60 liters (density of water = 1).
    • ICF: ~40 liters.
    • ECF: ~20 liters.

Extracellular Fluid (ECF)

• Surrounds cells, also called the internal environment.
• Contains:
  • Ions: Sodium, chloride, bicarbonate.
  • Nutrients: Amino acids, fatty acids, glucose.
  • Waste Products: CO2 (expelled via lungs), other waste (excreted by kidneys).
• Circulation:
  • Arteries → Capillaries → Tissue diffusion → Veins → Heart.

Intracellular Fluid (ICF)

• Inside cells, containing water and ions.
• Different from ECF:
  • Common Ions: Potassium, magnesium, phosphate.
• Ion concentration difference between ICF and ECF is regulated.

Next Topic

• Upcoming video on Homeostasis (not to be confused with hemostasis).

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Conclusion

• Emphasis on safety, happiness, and diligent study.