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Lecture 4

Week 4 - MY Powerpoints

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Simon Fraser University
Biological Sciences
BISC 101
Derek Bingham

BIOL1103–W eek4 Homeostasis Integumentary System Glycoproteins Glycolipids • Attached to membrane • Attached to phospholipids proteins • Named for what they are attached to • NOT proteins or lipids • Sugar (carbohydrate) groups that are attached to the extracellular membrane surface Glycocalyx–“SugarCoating” • Collective name for the glycoproteins and glycolipids on the extracellular membrane surface • Functions as a cell identifier • Examples • e.g., liver has a different glycocalyx than the heart • Different blood types (A, B, AB, O) • Ribosomes produced at rough ER are destined for extracellular export so the ribosomes “search” for the correct glycocalyx of the cell they are destined for Homeostatis • Homeostasis – the condition in which the body’s internal environment remains relatively constant • Internal environment – environment that exists outside all cells of the body; sum of the extracellular fluid ExtracellularFluids Examples • Interstitial fluid • Lymph • Plasma Conditions of ECF • Proper concentration of gases, nutrients, and water • Optimum temperature and pressure • pH (acidity – H ions) Stress Any stimulus that causes an imbalance in the internal environment Examples • External causes of stress • Lack of oxygen • Excess heat or cold • Internal causes of stress • Changes in blood pressure • Change in levels of nutrients HomeostaticControlMechanisms a. Variable – regulated factor or event; the input; what’s changed (like an increase in blood pressure) b. Receptor – specialized cell that monitors changes in the internal and external environment (like baroreceptors in vessel walls); closely associated with the terminal of adjacent axons of particular neurons c. Control center – brain – determines set point for a variable; analyzes input and coordinates an appropriate output d. Effector – a muscle cell or gland that carries out the response directed by the control center NegativeF eedback • Output is opposite to input • Negates input • Used in homeostasis • Most common feedback • Prevents sudden or severe bodily change
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