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This is also the reason why we tend to look like our parents. Even though the genetic variability is huge, we only have the chromosomes our parents started out with3/8•Physiology and the Internal Environment
“The study of an animal and its component parts”Cells are very sensitive to the environment around them (pH, temperature, tonicity, etc. must be regulated very carefully)Homeostasis: maintenance of relative constancy of the internal environment•Negative Feedback Regulation of Plasma [Glucose]Plasma= blood minus the cell (liquid part of the blood)Clusters of cells inside the pancreas; 1 particular kind of cell is the βcell•βcells: sensors, control centers, effectors (a cell or organ that brings about an effect by taking an action•βcellsenses glucose levels and regulates an action as a resultHomeostasis: 90 mg glucose/100 mL blood Stimulus: blood glucose level rises after eating βcells release insulin glucose uptake in cellsSpecific mechanism: Insulin stimulates the cell to insert glucose transports into the membrane (facilitated diffusion transporters that allow glucose to cross the lipid bi-layer down its concentration gradient GLUT)Glucose can be converted to glycogen, and it becomes a pool of stored glucose that the body can draw on (for example, when you are sleeping)Eventually, these effects cause a DROP in glucose (negative feedback loop), which keeps glucose at homeostasis. Most control systems in biology are negative feedback systems.•Clicker Q: Which is not an example of negative feedback regulation?Low body temperature causes shivering (the point of shivering is to generate body heat) – negative feedbackSalty food triggers salt excretion (a rise in plasma glucose will stimulate sodium excretion through urine and feces) – negative feedbackStools in rectum stimulate defecation– positive feedbackExercise stimulates breathing (exercise produces a deficit of oxygen in the body and a build up of CO2 breathing blows off this CO2) – negative feedback•Cardiovascular systemsThe Heart•The Need for Circulatory SystemsoDiffusion is adequate only over short distancesoTiny, flat, or porous animals can live without a circulatory systemsoParamecium DOES have a circulatory system—constantly circulating a cytoplasmoGlucose can diffuse about 100 micrometers in one second—not fast enoughoHearts are PUMPSPumps create pressure gradients in fluidsFluids (liquids and gases, e.g. blood) flow down pressure gradientsSo, at the downstream end of blood vessels, BP is lowHeart restores BP to enables re-circulationLeft side of the heart is pumping blood into the aorta (HIGH pressure), then into the artieries, then into arterioles, then into capillaries, then into venuoles, then into bigger veins, then back to the heart on the right side of it (LOW pressure). This must be because of a pressure gradientUnits are mms of mercury
Maximum pressure of the heart: systolic pressureMinimum pressure of the heart: diastolic pressureoClicker Question