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BIOL 1412 (89)
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BIOL1412 01 08 2014.docx

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Department
Biological Sciences
Course
BIOL 1412
Professor
Paul Messing
Semester
Winter

Description
BIOL1412 01 08 2014 Homeostatic Regulation a) Negative Feedback - Most common homeostatic control mechanism - Result of "output" - variable moves back toward the set point ie. in opposite (neg.) direction to the change that triggered the response ("input") - eg. body temp. ( = variable) set point 36 to 37.8° C If ⇑ temp. (eg. 40° C) "input" "output" hypothalamus ⇒ Brain ⇒ E=smooth thermostat muscle of cells (r) blood vessels detect high in skin relax temp. (stimulus) (causing dilation) + sweat glands secrete sweat - Result = core blood to skin surface and sweat evaporates = ⇑ heat loss and ⇓ temp. (opposite direction of input) eg. 2 ⇓ temp. ⇒ shiver ⇒ ⇑ temp. - set point can change eg. fever = cause by bacterium b) Positive Feedback - less common - NOT homeostatic - output intensifies the input (enhances it) eg. childbirth - labour * uterine contractions ⇓ +ve feedback = NS ⇑ contractions ⇓ posterior pituitary gland ⇓ releases oxytocin (hormone) - *con'ts until endpoint ( = baby born) Topic 2: Cell Physiology I The Cell Membrane (Fig.3.3) 1) Phospholipid Bilayer - con't-ous layer around the cell - barrier to H2O soluble substances - NOT to small mol.s (O2 & CO2) & lipid soluble mol.s 2) Membrane Proteins a) Transport Proteins
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