Human Physiology Overview

Cell Physiology

• Study of human organs and cells
• Understanding human physiology is crucial for various fields like medicine and fitness.
• Physiology investigates how organs and systems within the body work, how they communicate, and the combined efforts for survival.

What is Physiology?

• It studies how organs and systems function within the body.
• It examines the communication and coordination of these systems to maintain favorable conditions for survival.
• Physiology is essentially the study of life, examining how organisms operate internally and interact with their environment.

Major Systems Covered in Human Physiology

• Circulatory system
• Digestive/excretory system
• Endocrine system
• Musculoskeletal system
• Nervous system
• Renal/urinary system
• Reproductive system
• Respiratory system

The Cell: Basic Living Unit

• The cell is the fundamental unit of life within the body.
• Each organ is an aggregate of many cells interconnected by supporting structures.
• Every cell type is specially adapted to perform unique functions.

Organization of the Cell

• A typical cell, as viewed under a light microscope, comprises two major components:
  • Nucleus: Separated from the cytoplasm by a nuclear membrane.
  • Cytoplasm: Separated from the surrounding fluids by a plasma membrane.
• The various substances within the cell are collectively called protoplasm.
• Protoplasm mainly consists of water, electrolytes, proteins, lipids, and carbohydrates.

Physical Structure of the Cell

• Cells contain highly organized physical structures called organelles.
• The physical characteristics of each organelle are as vital as its chemical composition for proper cellular function.
• Figure 1 illustrates the key organelles and structures within a cell.

Cell Organelles (Detailed Information follows)

• Endoplasmic Reticulum (ER):
  • Rough ER (RER): Abundant in protein-secreting cells, involved in protein synthesis.
  • Smooth ER (SER): Associated with steroid hormone production and detoxification, especially in endocrine glands.
  • Sarcoplasmic Reticulum (SR): Crucial for muscle contraction and relaxation.
• Ribosomes: Protein synthesis, often bound to the endoplasmic reticulum.
• Golgi Apparatus: Protein glycosylation (addition of carbohydrates).
• Lysosomes: Breakdown of damaged or dead cellular components.
• Peroxisomes: Similar to lysosomes in function, primarily involved in detoxification.
• Mitochondria: Energy production for the cell (ATP).
• Nucleus: Control center of the cell, containing genetic information (DNA).

Membrane Transport (Detailed Information follows)

• Transport of Materials Across Plasma Membrane

  • Various methods exist for material transport, including: diffusion, osmosis, active transport, and transportation of large molecules.
    • Passive Transport: Includes simple diffusion (movement across a membrane according to a concentration gradient) along with facilitated diffusion (movement with the assistance of a carrier protein), both types require no energy input.
    • Active Transport: Moves molecules against their concentration gradient, requiring energy (e.g., Na-K pump).
    • Transport of Very Large Molecules: Includes endocytosis (cell taking in materials).

• Factors Influencing Passive Transport (Osmosis, diffusion) - Solubility of molecules, size of molecule, charge of molecule, concentration gradient, surface area.

• Osmosis: Movement of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration.

• Isotonic solutions: solutions with the same concentration of solutes inside and outside the cell , keeping the cell size normal.

• Hypertonic solutions: solutions with a higher concentration of solutes, causing water to leave the cell.

• Hypotonic solutions: solutions with a lower concentration of solutes, causing water to enter the cell.

• Types of Endocytosis

• Pinocytosis: Ingestion of fluids and dissolved substances.

• Phagocytosis: Ingestion of large particles (bacteria and other debris)