Homeostasis across Body Systems Evolution Notetaker Instructions You

Homeostasis across Body Systems & Evolution Notetaker Instructions: You and your partner will paraphrase— NOT copy—during the powerpoint lecture

Homeostasis O Homeostasis is a steady, yet dynamic state. O Homeostatic systems consist of: O receptor(s), control center, effector(s. ) O There are 2 primary homeostatic systems: O Positive Feedback: An increase in product results in increasing the rate of the synthesis of that product. This is the “finish what you started” mechanism. O Ex: A B C D; where the synthesis of D activates the enzyme A B “ase” thereby increasing rate of D O Negative Feedback: An increase in product results in a decrease in synthesis of more product. This is the mechanism by which levels of a substance remain relatively constant continually O Ex: A B C D; where the synthesis of D acts as an allosteric enzyme of the enzyme A B “ase” thereby stopping process

Positive Feedback: examples O Release of hormone, oxytocin causes the uterus to begin contracting. The contracting uterus pushes the baby and increases pressure on the opening of the uterus (cervix). This increase in pressure results in release of additional oxytocin which will increase contraction strength and intensity. . . which will increase pressure on the cervix. . . which will increase oxytocin release O Blood clotting, complement proteins in the immune system, and inflammation are additional examples of positive feedback loops.

Negative Feedback: examples O Blood glucose—you know this O Hemoglobin (Hb)- responds to heat and acidity. O Hb will begin to change shape as it encounters warmer or more acidic environments. O These fully reversible, slight changes in shape result in a decreased affinity for O 2. Exercising muscles are warm (friction) and acidic (lactic acid). Hb will therefore “know” to drop off more O 2 molecules at muscles that are contracting due to exercise.

Homeostasis: Thermoregulation O Why does an organism typically have such a narrow temperature range in which it can live? O Enzymatic reactions, protein shape, and other biochemical events all occur optimally in a specific temperature range. O Excessively high temperature may denature enzymes O Sharp decrease in temperature may result in too few collisions of reactants. O Endotherms & Ectotherms: O Endotherms (warm blooded) are able to maintain a steady body temperature regardless (to some extent) of environmental temperature. O Examples? O � Ectotherms (cold-blooded) are at the mercy of external temperature and must find other means to regulate body temperature O Examples?

• Partner A: A Explain to your partner what is going on with the mouse in this graph—use quantitative evidence from the graph • Partner B: Agree or Disagree? Explain to your partner what is going on with the lizard in this graph—use quantitative evidence from the graph • Partner A: Agree or Disagree?

Methods of Temperature Regulation O Evaporative Cooling O Raising your body temperature provides the heat needed to cause sweating, which cools the body O Controlling heat exchange O Dilation of blood vessels near the surface of the skin will receive the benefits of the evaporative cooling (sweating) O Increasing body temperature O Shivering, flapping of wings O Behavior O Ectotherms—movement to a warmer location O Acclimiation O Ability to produce specialized proteins--anti-freeze genes in artic fish & higher altitude tolerance, O Nonpermanent change

Homeostasis: Maintaining H 20 balance O Osmoregulation (water regulation) based largely on shuffling solutes and H 2 O between internal and external fluids. O Organisms must rid themselves (excretion) of toxic, nitrogenous waste resulting from protein catabolism. O Excretion of nitrogen waste: O Water dwelling organisms convert amino groups into ammonia (NH 3) and may simply excreted through diffusion via skin, gills, etc O Land dwelling organisms are forced to store nitrogenous waste for extended periods of time before excretion is possible. NH 3 is extremely toxic. Ammonia is modified in the liver and converted to urea. Urea is less toxic than NH 3 and can be stored more safely. In addition, urea is extremely water soluble.

Osmoregulation: Land-dwellers O Whether an earthworm, insect, or mammal the basic system to regulate water follows this: O Filter Reabsorb what is valuable Secrete toxins Excrete O More complex system in more complex organisms but follows the same pattern

Osmoregulation: Land-dwellers--Mammals O THE MIGHTY KIDNEY! O Physical filtration due to pressure across capillaries. O Filtrate proceeds into the Bowman’s capsule O The loop of Henle descends down and back up through the renal cortex and medulla. O The deeper portions of the medulla are more concentrated in salt and urea resulting in various stages of osmosis, diffusion, and active transport as primarily H 2 O is reabsorbed (98 -99% of all H 2 O in the filtrate is reabsorbed). O Excretion occurs when the “remnants” travel through the collecting duct and are eventually passed as urine