Physiology (9)

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Physiology (9)

  1. 1. Physiology Cell Membrane/Plasma Membrane • functions: 1. integrity of the cell 2. controls transport = “selectively permeable” 3. excludes unwanted materials from entering the cell 4. maintains the ionic concentration of the cell & osmotic pressure of the cytosol 5. forms contacts with neighbouring cells = tissue • lipid bilayer - with embedded proteins and carbohydrates • about 75% of these lipids are phospholipids • also made up of cholesterol and glycolipids • ion channels = gates for specific ions only -open in response to: 1. changes in voltage 2. binding of a ligand e.g. calcium, sodium, chloride, potassium -affected by drugs e.g. anti-hypertensives - calcium, potassium local anesthetics - sodium diuretics - sodium muscle relaxants - chloride anti-diabetics - potassium -disease states affect channel function e.g. cystic fibrosis Membrane function: 1. Physical isolation - from the surrounding ECF -allows the cell to create different environments outside and inside 1
  2. 2. -allows for the creation of gradients – electrical and chemical 2. Integrity of cell - cell shape and size -increase cell size, increase surface area/volume -increase exchange surface 3. Sensitivity - first part of cell that is affected by changes in the extracellular environment 4. Structural support - connections between cells provides tissues with support and stability 5. Controls transport = “selectively permeable” -two types: Passive - Diffusion, Osmosis, Facilitated Active - Active transport, Exocytosis, Endocytosis, -Osmosis is controlled by tonicity = degree to which a the concentration of a specific solute surrounding a cell causes water to enter or leave the cell hypertonic 2

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