Lecture 1 Homeostasis: Why things don’t (usually) go wrong! Homeostasis: • Maintain stability of internal environment (fluid bathing cells) in face of changes to external & internal environment by body systems • Blood pressure, body temperature, water content, food intake, etc. BODY FLUID COMPARTMENTS TOTAL BODY WATER (TBW) = 60% BWkg Normal BW 70 Kg so TBW = 42 L INTRACELLULAR FLUID Volume = 28 L, 2/3 TBW H 2O INTERSTITIAL FLUID Volume = 11 L 80% of ECF H 2O H2O SALTS PLASMA Volume =3L 20% of ECF H2O SALTS EXTRACELLULAR FLUID Volume = 14 L, 1/3 TBW Homeostasis: Why things DON’T (usually) go wrong! Homeostasis: • Stability – balancing inputs & outputs • dynamic compensatory processes • Keep regulated variable within normal range • Cell function maintained by constancy of internal environment (ECF): pH, volume, ionic composition, energy level COMPONENTS OF FEEDBACK SYSTEMS Stimulate or inhibit Start 1 4 Stimulate or inhibit 2 3 Stimulate or inhibit NEGATIVE Feedback System 1. Response of body in opposite direction of change in that variable 2. Most variables in body under negative feedback control 3. Blood pressure, blood glucose, body temperature POSITIVE Feedback System 1. Response of body in same direction of change in that variable 2. Exacerbates or amplifies change 3. Rare in body – destabilizing 4. Blood clotting, nerve & muscle action potential, parturition Intracellular Homeostasis 1. Ionic Homeostasis • Cell membrane integrity • Passive transport • Diffusion, osmosis, filtration • Active transport • 10, 20, co- & countertransport • Membrane potential to maintain internal environment: • Channels & transporters • Nutrient & waste transport Fig 4.15 Intracellular Homeostasis 2. Volume homeostasis • ECF stabilizes ICF 3.pH Homeostasis • Enzyme regulation • Metabolic control 4.Energy Homeostasis • [ATP] regulates energy flux Lecture 2 TERMINOLOGY: • Tonicity–qualitative-relativeconcentration of 2 solutions thatdetermines the direction and extent ofdiffusion of water • Isotonic soln: no net diffusionof water • Hypotonic soln: water moves into cells causing them toswell • Hypertonic soln: water moves out of cellscausing them toshrink Tonicity-Relative Response of Cells in Solution TERMINOLOGY: • Isosmotic- sameosmolarity as plasma • hypoosmotic - below • hyperosmotic - above Major Cations & Anions TERMINOLOGY: • Oncotic pressure ( ; mmHg)–a type of osmoticpressure generated bymolecules too large to crosssemipermeable membranes(usuallyproteins): “pullingpressure” • Hydrostatic pressure (P; mmHg)–pressureexerted by gravity effects orpumping ofliquids:“pushing • pressure,”e.g. bloodpressure Body Fluid Compartments Terminology • Oncotic pressure (pi; mmHg)– a type of osmotic pressure generated by molecules too large to cross semipermeable membranes (usually proteins) • “Pulling Pressure” • Hydrostatic pressure (P; mmHg)– pressure exerted by gravity effects or pumping of liquids • “Pushing Pressure” e.g. BP IV Fluids • Main types of IV Fluids – Isotonic fluids – Hypotonic fluids – Hypertonic Fluids • Groupings of IV Fluids – Blood & blood products – Crystalloids: electrolytes – Colloids: create oncotic pressure, albumin – Plasma expanders Lecture 3 Solubility in Water Molecules with ionic or polar covalent bonds have an electrical attraction to water molecules. Fig 2.4 • When NaCl is placed in water, the polar water molecules are attracted to the charged sodium and chloride ions. • Clusters of water molecules surround the ions, allowing the sodium and chloride ions to separate from the salt crystal and enter the water… or to DISSOLVE. Lipids Lipids are non-polar and have a very low solubility in water. Lipids can be divided into four subclasses: Cholesterol/steroids Fatty acids Triglycerides Phospholipids Lipids provide a valuable source of energy, are a major component of all cellular membranes and are important signaling molecules. Phospholipid Bilayer *Image via Bing This is our CELL MEMBRANE!!