physiology

• Physiology


  The study of the normal functions of living organisms and how they are regulated and integrated
• Physiology is an integrative science that studies about the normal functions of complex living organisms at levels ranging from molecules and cells to organs and systems
• For a person to remain healthy, physiological conditions in the body must be kept at optimal levels and closely regulated
• Basic physiological functions


  • Motion
  • Digestion
  • Excretion
  • Respiration
  • Reproduction
  • Body defence
  • Sensation
  • Mental functions
• Nature of Physiology


  • It is an Integrative science
  • It is a Multi-disciplinary field
  • It is an Experimental science
  • It is a Quantitative science
• William Harvey laid the foundation of physiology by describing correctly about the "circulation of blood" in human body


  1578-1657
• Claude Bernard introduced the modern thought of physiology called ECF


  1813–1878
• Walter Cannon termed the maintenance of constant conditions in the ECF as homeostasis


  1871–1945
• Levels of Body Organization

  • Chemical
  • Cellular
  • Tissue
  • Organ
  • System
  • Organism
• Each system in the body is independent structurally but functionally all the systems are interdependent
• Cell


  The basic, living, structural & functional unit of body
• There are nearly 100 trillion cells in an average adult
• Most disease processes are initiated at the cellular level, an understanding of cell function is crucial to understanding the disease process
• Common Characteristics of Cells

  • Needs nutrition and oxygen
  • Grow, repair & die
  • Eliminates carbon dioxide and other metabolic wastes
  • Shows immediate response to the entry of invaders like bacteria or toxic substances into the body
  • Reproduces by division
• Parts of a Cell

  • Cell membrane
  • Nucleus
  • Cytoplasm
• Organelles


  Cellular structures embedded in the cytoplasm with definite structure and specific functions
• Modes of intercellular communication

  • Direct communication (through gap junction or pores)
  • Autocrine (self cell)
  • Paracrine (near cell)
  • Neural
  • Hormonal
  • Neuro-hormonal
• Apoptosis


  The natural or programed death of the cell under genetic control
• Necrosis


  The uncontrolled and unprogramed death of cells due to unexpected and accidental damage
• Functions of Plasma Membrane

  • Protective function
  • Selective permeability
  • Absorptive function
  • Excretory function
  • Exchange of gases
  • Maintenance of shape and size of the cell
• Chemical Composition of Plasma Membrane

  • Proteins (55%)
  • Lipids (42%)
  • Carbohydrates (3%)
• Proteins and lipids are two major components of the plasma membrane
• The phospholipid bilayer consists of two adjacent sheets of phospholipids, arranged tail to tail
• The polar heads of the phospholipids contact the fluid inside and outside of the cell
• Membrane Transport Mechanisms


  • Simple Diffusion
  • Facilitated Diffusion
  • Osmosis
  • Active Transport
  • Vesicular Transport
• Simple Diffusion


  Movement of substances down their concentration gradient, requires no direct expenditure of metabolic energy (ATP)
• Facilitated Diffusion


  Movement of substances down their concentration gradient, using carrier proteins in the membrane
• Osmosis


  The movement of water from an area of higher amount of water (less concentrated solution) to an area of lower amount of water (high concentrated solution) through a semi-permeable membrane
• Active Transport


  Uses metabolic energy (ATP) to drive solute transport against their concentration gradient
• Primary Active Transport


  Carrier protein is involved, consumes energy directly from ATP
• Secondary (Coupled) Active Transport

  Carrier protein is involved, consumes energy indirectly (from Na+ concentration difference or potential energy)
• Types of Active Transport

  • Symport (transports two molecules in the same direction)
  • Antiport (transports two molecules in opposite directions)
• Vesicular Transport


  Movement of large molecules (macromolecules) that cannot be transported by primary or secondary active transport
• Endocytosis


  The taking in of molecules or particles by invagination of the cell membrane forming a vesicle
• Phagocytosis


  The engulfing of large particles such as food particles and bacteria by forming a vesicle
• Exocytosis


  The release of macromolecules synthesized in the cell to the outside of the cell
• The approximate composition of an average adult human per body weight is: Water = 60%, Proteins = 18%, Fats = 15%, Minerals = 7%
• Body Fluid Compartments


  • Extracellular Fluid (ECF)
  • Intracellular Fluid (ICF)
  • Transcellular spaces
• Intracellular fluid (ICF) is two-thirds of Total Body Water (TBW), Extracellular fluid (ECF) is one-third of TBW
• The ECF is essential for the life of the cell as it contains the ions and nutrients needed by the cells to maintain cell life