Part 2

• Physiology


  The study of the normal functioning of a living organism and its component parts, including all its physical and chemical processes
• Emergent properties


  Properties of a complex, non-linear system that cannot be explained by knowledge of its parts
• Levels of organization in physiology

  • Molecules
  • Cells
  • Tissue
  • Organs
  • Organ System
• Function


  'Why' or a teleological approach
• Mechanism


  'How' or a mechanistic approach
• Physiology favours a mechanistic approach
• Homeostasis


  Maintaining a stable internal environment despite external changes. Homeostasis does not mean equilibrium, rather it is in a dynamic steady state or a stable disequilibrium
• Examples of external changes

  • Toxic chemicals
  • Physical trauma
  • Foreign invaders
• Examples of internal changes

  • Abnormal cell growth
  • Autoimmune disorders
  • Genetic disorders
• Pathophysiological state


  Occurs when compensation fails and results in a state of sickness
• Internal environment of the body

  Extracellular fluid: the buffer between cells and the external environment
• Dynamic steady state


  Movement of materials back and forth with a substance with no net movement within the substance
• Law of mass balance


  The amount of a substance in the body is to remain constant. Any gain must be offset by an equal loss
• Local control


  Restricted to the tissues or cells involved
• Reflex control


  Changes widespread throughout body (systemic) and uses more complex control systems to maintain homeostasis. It is any long-distance pathway that uses the nervous, endocrine system, or both. It has an acceptable set point and can be antagonistic. It contains two parts; the response loop and the feedback loop (which modulates the response loop and feeds back to ultimately influence the input)
• Types of feedback loops

  • Negative feedback loop: a pathway in which the response opposes or removes the signal. It stabilizes a system, is homeostatic, can restore the initial state
  • Positive feedback loop: reinforces the stimulus to drive the system away from a normal value rather than decreasing or removing it. It is not homeostatic. Requires intervention or event outside the loop to cease the response
  • Feedforward control: a few reflexes have evolved to allow the body to predict that a change is about to occur
• Biorhythms


  Variables that change predictably and create repeating patterns or cycles of changes. Can vary within an individual over time
• Anatomical compartments


  • The Cranial cavity
  • The thoracic cavity (pleural sac and pericardial sac)
  • Abdominopelvic cavity (Abdominal cavity and Pelvic cavity)
• Functional compartments


  • The Extracellular fluid (Blood plasma and Interstitial fluid)
  • Cells - Intracellular fluid (intracellular compartments)
• Functions of a cell membrane

  • Physical isolation: a physical barrier separating ICF and ECF as well as cell from environment
  • Regulation of exchange with the environment: Controls entry, elimination and release
  • Communication between the cell and its environment: contain proteins that allow for responding or interacting with the external environment
  • Structural support: proteins in the membrane are used to make cell-to-cell connections (tissue) and to anchor the cytoskeleton
• Cell membrane composition


  Proteins, lipids, and small amounts of carbohydrates. The more protein a membrane has, the more metabolically active it is
• Types of lipids in the cell membrane

  • Phospholipids
  • Sphingolipids
  • Cholesterol
• Fluid mosaic model


  Proteins are dispersed throughout the membrane, and the extracellular surface contains glycoproteins and glycolipids
• Integral proteins


  Transmembrane proteins, Lipid anchored proteins. Roles: Membrane receptors, Cell adhesion molecules, transmembrane movement, Enzymes, mediators of intracellular signalling
• Peripheral proteins


  Attach to integral proteins or loosely attached to phospholipid heads. Roles: Participate in intracellular signaling, form submembraneous cytoskeleton
• Lipid rafts


  Sphingolipid clusters with a high cholesterol content and high abundance of proteins. Planar lipid raft (Flotillin), Caveolae (Caveolin). Important in cell signal transduction
• Functions of glycoproteins


  • Structural molecule
  • Transport molecule
  • Immunologic molecule
  • Hormone
  • Enzyme
  • Cell to cell recognition
• Glycolipids


  Serve as recognition sites for cell-to-cell interactions
• Total body water


  60% of the body. 2/3 ICF, 1/3 ECF (1/4 Plasma, 3/4 Interstitial Fluid)
• Osmotic equilibrium


  Fluid concentrations are equal; the amount of solute per volume of solution is equal
• Osmosis


  The movement of water across a membrane in response to a solute concentration gradient
• Locations of solutes


  • Intracellular Fluid: High K+ and Proteins
  • Interstitial fluid: High Na+ and Cl-
  • Plasma: High Na+ Cl-, and Proteins
• Osmotic pressure


  The pressure that would have to be applied to oppose and prevent osmosis
• Osmolarity


  The overall solute concentration of a compartment, takes into account all solutes in the compartment, penetrating and non-penetrating. (relative/comparable term)
• Osmotic states


  • Isosmotic: equal
  • Hyperosmotic: higher osmolarity
  • Hyposmotic: lower osmolarity
• Tonicity


  How a solution would affect cell volume if a cell were placed in the solution and allowed to come to equilibrium. Concerned with non-penetrating solutes only
• Tonicity states


  • Hypotonic: Burst/Swell (cell has low solute concentration)
  • Isotonic: Equal concentrations
  • Hypertonic: Shrivelled (cell has low solute concentration)
• Diffusion


  The movement of molecules from an area of higher concentration to an area of lower concentration
• General properties of diffusion

  • Diffusion does not require and outside energy source
  • Diffuse from an area of high to low concentration
  • Diffusion continues until concentrations come to equilibrium
  • Diffusion is faster along higher concentration gradients, shorter distances, higher temperatures, for smaller molecules
  • Can take place in an open system or across partition
• Simple diffusion


  For small uncharged molecules. Rate of diffusion is faster if the membranes surface area is larger, the membrane is thinner, the concentration gradient is larger, the membrane is more permeable to the molecule. Membrane permeability depends on the molecules lipid solubility, size, and the lipid composition of the membrane