BIOL 4505 1st EditionExam # 2 Study Guide Lectures: 10 - 18Lecture 10 (September 19)Although the temperature of two organisms can be the same, heat is dependent on the mass of each. For the body temperature of an animal to be constant, heat gains must = heat losses. When a poikilotherm maintains a relatively constant body temperature, that is called behavioral thermoregulation. Behavioral is limited by the thermal opportunities inside the environment, and so must be capable of functioning at a variety of temperatures. Eurytherms = function over wide rangesof body temperature, stenothermal = narrow ranges.Metabolic rate is an exponential function of body temperature. The relationship between metabolic rate and body temperature is logarithmic. After chronic exposure, partial compensation can occur afteracclimation. Temperature directly affects the processes within an organism, such as the enzyme-substrate affinity must be kept relatively constant, as is the fluidity of the lipid bi-layer. Species with evolutionary histories in different environments often synthesize different molecular forms of protein molecules and different suites of cell-membrane phospholipids.Lecture 11 (September 22)A special case is that tuna are able to keep their bodies warm by exchanges in the blood that keep heat in tissue. Bloodflow without countercurrent heat exchange allows blood to lose heat slowly to the environment. Bloodflow with countercurrent heat exchange allows some of the heat lost from the arterial blood to short-circuit and enter the venous blood. Behavioral defenses include making burrows, resting during the heat of the day. Insulatory defenses involve the organism of the body acting as heat shields. Wild warm-bodied fish exhibit greater temperature differentials than captive fish. The bluefin tuna is an endothermic regulator, while the skipjack and yellowfin are endotherms without thermoregulation. Rete mirabiles are complex nets of veins, present in seals and whales as well. The regulation that occurs in billfish, sharks, and tunas are only in certain body parts such as the red swimming muscles, sometimes the stomach and brain, and the retinas. The heat source is metabolic heat except for billfish, which have “heaters” in their eye tissues.There are three methods in which ectotherms deal with low temperatures: Freeze tolerant who affectthe ice formation in their bodies, freeze intolerant who do not survive, and freeze avoiders who withstand by use of supercooling and specialized ice formation. Cells rupture when they are frozen, and ice crystals are sharp, which puncture the cell membrane. Ice also expands when frozen, and forms very rapidly. The goals of a freeze-tolerant animal are: 1) to freeze slowly and organize ice crystals in a less sharp shape, 2) freeze extracellular fluid, 3) use protein isonucleating agent with a hydrophilic center. Solutesare excluded from the ice formation, which increases the solute concentration and osmolarity, and decreases the freezing point. Colligative cryoprotectants are membrane protectants that keeps H2O out where it would usually bind. Endotherms have a zone of metabolic regulation. Upon graphing, an organism with less insulation with have a much steeper slope than one with high insulation. The greater the insulation, the greater the thermal neutral zone. The best insulation an endotherm can have is trapped air. Fur can serve to trap air, followed by fat. Fat is not the best insulator there is because its properties are closer to water. Blubber (fat) requires shunt vessels and surface vessels with a small skin layer. An endotherm might have the same amount of insulation in the summer as it does in the winter, but the peak metabolic rates will rise in winter due to thermoregulating in winter. Another organism might have far greater insulation in the winter than summer, so therefore the resting rate of 02 consumption will differbetween seasons. This is because arctic species will spend less energy to thermoregulate in cold temperatures than a species from the tropics (steeper slope with smaller metabolic range). Endotherms can undergo torpor and hibernation with a 100% to 7% resting metabolic rate by maintaining a body temperature above 0 degrees, around the air temperature. Vasoconstriction results in response to cold temperatures, while vasodilation results in response to warmth.Lecture 12 (September 24)Examples of ions in the body are: Na+, Ca2+, Cl-, K+ and are all charged particles. Current is the flowof charges. Voltage is the potential difference across two points; separation of positive and negative charges. Resistance limits the current or flow. Conductance is the ability of flow; opposite of resistance. Increasing the number of channels decreases the resistance. An increase in flux is an increase in the number of “doors” for the ions. Equilibrium will occur if diffusion goes long enough, which sets up the situation for the Donnan Equilibrium. As ions diffuse out, some are pulled back in because of the negative electrical gradient. The voltage difference across membranes inside measures-70 mV.The membrane potential is the charge difference of electrical potential across the cell membrane (Vm). These are selectively permeable membranes, like K+ leak channels. The membrane potential is calculated by the Nernst Equation, which describes equilibrium/diffusion potential of one ion and explains the relationship between chemical and electrical gradients. The resting potential (Vrest) is the membrane potential of a non-excited cell from -20 to -100mV due to channels, and unequal concentrations in and out of the cell. A Vm of -70mV with channels added to it will become -90mV, whereas removing channels would bring it to -40mV. The Goldman Equation describes a Vm for multiple ions, permeability of each ion, and provides a better estimate of the Vm.During depolarization, neurons make their membrane potentials positive by opening the channels. During repolarization, neurons make their membrane potentials negative by closing the channels, pumping them out, or by opening more K+ channels. The information transferred is a charge change very similar to the binary code (0 and 1) of computers. The channel that lets Na+ and K+ in are voltage gated channels.Lecture 13 (September 26)Neurons are nerve cells with long cable-like processes called axons that bring electrical signals (action potentials) to the rest of the body. Two types of integration are