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Prof Woods Unit 1 Summary Notes.docx

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Western University
Physiology 1021
John Ciriello

Homeostasis, Membrane Transport & Excitable Cells Summary Organ Systems Continuous with External Environment:  Respiratory  Urinary  Reproductive  Digestive Homeostasis:  Ability of the body to maintain a relatively constant internal environment  Regulated through negative feed back loops o Decrease the impact of change Body Fluids:  Extracellular fluid (interstitial fluid + plasma) – bathe cells o Act as a transition between external environment and intracellular fluid  cytoplasm o “Salty Bananas” Cellular Structure: Smooth ER: Makes lipids and fatty acids Centrioles: Cell division  splitting equally  directing DNA Golgi App: Modify/Package Proteins Rough ER: Manufacture protein Cytoskeleton: Provide support, enable motility Mitochondria: ATP Lysosome: digest bacteria and old organelles Nucleus: DNA Cell Membrane:  Maintain ion gradients  Selectively Permeable  Cell Signaling:  Long distance = ESSENTIAL for homeostasis o Nervous and endocrine coordinate many homeostatic functions  Metabolism, heart rate, body temperature o Chemical and electrical communication  Neurotransmitters: o Chemical signal: neuron  target cell o Only affect cells with receptor for chemical  Hormones: o Endocrine  bloodstream  target cell (with receptor)  Neurohormones: o Neuron  bloodstream  target cell (with receptor) Chemical Mediated Cell-Cell Communication:  Autocrine: cell makes and uses signal  Paracrine: signal acts on neighboring cells  Cytokine: chemical signal made by any cell in response to stimuli Contact-Dependent Signals:  GAP Junctions: o Protein channels form cytoplasmic bridges o Direct transfer of chemicals and electrical signals o Protein “connexin” Cell Membrane in Communication:  Must pass through in order to be processed o Ion channels o Enzymes o Receptors  Hormone/neurotransmitter o Membrane Carriers  Membrane Transport: o Endo/exocytosis o Diffusion  Movement of molecules from an area of high conc. To lower conc. Due to random thermal motion  Passive Process  At equilibrium: no net movement  No energy required  Lipid bilayer  Protein channels  Facilitated  Protein carrier – binds to specific molecule carried to other side of membrane  Competitive inhibition o Active transport  Requires energy  Chemically specific  Limited capacity Factors Affecting Diffusion Rate:  Conc. Gradient  Surface area  Molecule size  Membrane thickness  Lipid solubility of molecule OSMOSIS:  Movement of water across a membrane in response to a solute conc. Gradient  Dilute the more concentrated solution  Factors:
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