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Chapter 1 & 6:Homeostasis 9/5/14 7:33 PM Homeostasis- keeping internal environment stable relative to the outside Law of mass balance- what comes in must equal what comes out Two options: Excretion- elimination of material from the body Convert substances through metabolism Mass flow=concentration of x * volume flow Clearance-rate at which something leaves the body.

Physiology Notes

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Chapter 89/5/14 7:33 PM

Homeostasis- keeping internal environment stable relative to the outsideLaw of mass balance- what comes in must equal what comes out Two options:Excretion- elimination of material from the bodyConvert substances through metabolismMass flow=concentration of x * volume flowClearance-rate at which something leaves the body.

Homeostasis is not equilibrium Instead its a dynamic steady state To maintain the body regulates certain variables at a setpoint There is an input signal, integrating center, output signal then a response

Local control- starts in one tissue and is handled in that tissueReflex control uses long distance signaling Two parts: a response and feedback loop Three parts to a response loop: input signal, integrating center and an output signal

Negative feedback loops are homeostatic Positive feedback loops are not homeostaticFeedforward loops anticipate change

Chapter 1 & 6:Homeostasis9/5/14 7:33 PM

Tonicity: how cell volume would be affected if placed in a certain solutionHypotonic- cell gains waterHypertonic-cell loses waterIsotonic-nothing happens Tonicity depends on the concentration of non-penetrating particles only Diffusion: Passive transport that uses kinetic energy of molecules Higher to lower concentration-down concentration gradientOccurs until the concentration is equal everywhereFaster over short distancesFaster with high temperaturesFaster with smaller particles Diffusion directly across a phospholipid bilayer is called simple diffusionOnly nonpolar lipophilic molecules can diffuseException is water-depends on concentration of membraneRate of diffusion is determined by surface areaFicks law of diffusion and membrane permeability determine diffusion rate

Protein-Mediated Transport-carried out by transporters 4 classes: structural proteins, enzymes, receptors and transportersStructural proteinsConnect membrane to cytoplasmCreate cell junctionsAttach cells to the extracellular matrixTransport proteins are either channel or carrier Most channel ones are water filled Selectivity of a channel protein is determined by the diameter and the amino acid charge of the protein its membrane

Facilitated Diffusion uses carrier proteinsFor example GLUT transporters Takes advantage of concentration gradientActive transport is opposite-requires energyDown concentration gradient Primary uses ATP, secondary freeloads by using the concentration gradient potential energy of another moleculeSodium-Potassium pump-primary active transport SGLT transporter-secondary

Vesicular TranportPhagocytosis-think amoebaEndocytosis-creates smaller vesicles

Chapter 5: Membrane Dynamics9/5/14 7:33 PM