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Lecture 5

AN100 Lecture 5: BIO 111 Final Study Guide (Autosaved)

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Wilfrid Laurier University
Amalia Philips

BIO 111 Final Study Guide ❖ THERMAL PHYSIOLOGY o Thermal physiology is how animals adapt to temperature change in the environment. Fur has insulating power, depending on thickness. EX: Animals that live in very cold places have thick fur. But why do animals that live in hot places like African mammals need to have fur as well? • Metabolic Rate o If you are interested in the energy usage by animals, the standard way to look at that is by measuring metabolic rate. Metabolic rate is the amount of energy released by the animal. o Old method called Direct Calorimetry: which is measuring energy lost as heat by the animal, or heat production. It happens like this: 1) place animal in a chamber, 2) surround it with ice, 3) measure rate of melting of ice, which gives an estimate of rate of heat production. o Since almost all animals are primarily aerobic metabolic organisms, you can use oxygen uptake as a proxy (representation) for metabolic rate, which is very common today. This is called Indirect Calorimetry: measuring the oxygen consumption gives you a good measure of the metabolic rate of the animal. o Smaller animals have higher (mass specific) metabolic rates. EX: shrews have a much higher metabolic rate pound per pound than an elephant. Why? This has to do with the ratio of surface area to volume. As an animal increases in size, that ratio decreases. The surface area is a major determinate of amount of heat loss to the environment. o EX: an animal with a small size and a large surface area that has to keep its body warm will have to have a very high metabolic rate because it is losing a tremendous amount of heat. (Shrews have to eat 10x their body weight every day to stay alive) o EX: contrarily, an elephant has a small surface area to volume ratio, so it loses less heat and can have a lower metabolic rate. • Animals’ Response to Changes in Environmental Temperature o Ectotherms (temperature conformity): have a body temperature similar to that of their surroundings. EX: if we change the temperature from 0° to 40° and measure the body temperature of a lizard, we’d find that if it was 20° outside, the body temperature of the lizard would be 20°. If it were 40° outside, the body temperature of the lizard would be 40°. o Endotherms (temperature regulator): maintain a fairly stable body temperature despite swings in the environmental temperature. They use their metabolism to maintain body temperature that is different from the environment. The cost is energy. The larger the difference between the body temperature and environmental temperature, the more energy it costs the animal to maintain that body temperature. EX: if its 10° outside, a bunny’s body temperature is 36°. If its 40° outside, the bunny’s body temperature is still 36°. At 38°, the bunny’s body temp is lower than the environment, so it has to cool its body by evaporative cooling (panting, sweating, etc.) o Heterothermy: some animals show intermediate behavior between endothermic and ectothermic. Heterothermic animals can maintain parts of their body at temperatures different than environmental temperature (usually above). EX: Sharks stay 5° warmer than the water he is in. What is the advantage of this? If it’s chasing a fish that has a lower body temperature than the shark, the shark’s muscles contract faster, therefore it can swim faster. • Circulatory Heat Exchange o In Heterotherms: heat exchangers in warm-blooded fish allow them to keep their body core temperatures higher than the ambient (surrounding area or environment). This is accomplished by a change in the anatomy of the circulatory system. EX: Typical cold-blooded fish have main blood vessels in the center of the body and the veins & arteries go out to the skin. But in heterothermic fish, the main blood vessels are under the skin and the capillaries beds are in the interior body core of the animal. This means blood coming back from the gills, where its been exposed to cold water, goes down into the body core and it warmed up by blood flowing in the opposite direction from the muscles. This keeps capillary beds warmer. o Countercurrent exchange systems require two fluids flowing in opposite directions in close proximity. EX: Fish gills perform countercurrent flow. They take up oxygen from water into the blood. The same idea is present in the process mentioned above: takes heat from warmer outflowing blood to the cooler blood going down into the body core. This keeps the animal’s body temperature slightly higher than the ambient water. o In Endotherms: many endotherms have heat exchangers. EX: Whales take in big amount of water and trap shrimp and food on their baleen plates. These animals spend much of their time in cold water. The tongue is highly vascularized with a lot of blood flowing through it, so this is a major site of heat loss for the whales while taking in cold seawater. If you look at the blood supply leading to the tongue, you’ll find a big artery surrounded by veins. Warm blood in the artery is going out to the tongue, which is exchanging heat with the cold blood in the veins gong back into the body core. This is a way to reduce loss of heat through the tongue. EX: Temperatures in the legs of waiting birds in cold water. The artery in the leg of these birds is surrounded by veins, which allows for heat exchange between warm arterial blood and the cooler venus blood. The animal isn’t losing as much heat through its legs, even though its legs are not insulated because they have no feathers. (So this process is how they make up for that. When feathers or fur get wet, they do not work as insulators.) o In desert animals: Desert animals still have heat exchangers. They use it to keep their brains cools. • Mechanisms of Energy Exchange with the Environment o Animals in the environment use radiation and convection (heat moving from one body to a fluid moving over that body) and evaporative cooling and energy flowing as heat from a warmer body in contact with a slightly cooler body all as mechanisms of energy exchange. The transfer of heat energy depends on: the temperature difference between animal and outside, surface area of the animal, and the transfer of heat through the skin. You can adjust the rate of movement of heat through the skin by adding fur to an animal. Insulating the skin reduces the rate of heat exchange. o Adaptations to extreme cold: o Can be: Homeoviscous, Behavioral, Antifreeze, Insulation, or Heat Exchangers 1. Homeoviscous – adaptations at the biochemical level in lipids. Has to do with maintaining the function of proteins in the plasma membrane. o EX: at lower temperatures, lipids are very tightly packed and ion channels can’t open to let ions through. This inhibits nerve action potentials. At very high temperatures, the lipids move around, therefore the proteins move around and do not function correctly. To make up for these temperature effects, organisms can change the composition of lipids in the plasma membrane two ways. One way is to change the amount of cholesterol in the membrane. Cholesterol affects the membrane fluidity by tying the lipids together (counteracting the effects of warm temperatures?). You could also change the fatty acid chain on the phospholipid molecules. C-C double bonds in the fatty acids makes kinks; many kinks means the lipids do not pack as tightly, which counteracts the effects of lower temperatures. These adaptations occur in animals chronically exposed to extreme temperatures. o EX: Frozen Frog: as soon as these frogs touch ice, signals are sent that pull water away from the center of the frog’s body, which rids them of water and turns them to solid ice. There is no kidney function or heartbeat for days or even weeks. The frog distributes its blood sugar through its circulatory system that keeps it alive, acting like antifreeze. When spring arrives, the animal comes back to life in 10 hours. The inside of the frog warms up before his outsides. It has freeze tolerance. 1. In the winter, a shrew (1-3 g weight) cannot eat enough to maintain its body temperature. 2. Shrews migrate to warmer latitudes in the fall. (T, F) *They hibernate instead 2. Behavioral – when it gets so cold that some endotherms cannot maintain their body temperature, they will go into: o Torpor – elastic heterothermy. In torpor, animals allow their body temperature to change depending on environmental conditions. There are different gradations of torpor. EX: Some animals go into a state where body temperature falls dramatically. Others can do this for a day or two. Others can sleep during the winter and their body temperature will not change. These are all ways to avoid heat loss in the winter. There is lot of variability. EX: Hummingbirds undergo diurnal torpor. When it gets cool at night, they’ll hang on a tree and let their body temperature decrease. (This is possible because of its surface area to volume ratio and their high metabolic rate.) They become active again in the morning. o Hibernation – found mostly in small rodents; animals allow their body temperature to fall from about 36° F to 15° or 20° F and become inactive. They do not stay this way for months. They rouse every 2-3 weeks and eat, then return to sleep. True hibernators are animals that allow their body temperature to fall by a large amount. EX: Bears are not true hibernators. A bear’s body temperature during winter sleep is the same as when it is active. Although their metabolic rate does drop, their body temperature does not fall like a squirrel. Bears usually give birth in winter, despite not eating. The fetus gets energy from fat reserves. Some black bears have stopped hibernating. 3. Antifreeze – When you get ice formation in the extracellular fluid, water freezes, and it excludes solutes. This increases the osmotic concentration in the extracellular fluid that is not frozen. This will draw water out of the cells, causing them to shrink to a damaged state. (Antifreeze animals can prevent this) o EX: Freeze tolerant animals like the frog have to control the ice crystal formation and make sure the ice crystals form outside of the cells. If they form on the inside, the sharp ice will poke edges into the cell membrane. The frog will break down glycogen and increase its glucose levels in the circulatory system. The cells will take up glucose, which will increase the osmotic concentration of the cytoplasm (in the cell). Then, as the extracellular fluid freezes, the cytoplasm will not lose water by osmosis to the extracellular fluid. o EX: Fish in cold water produce antifreeze molecules. There is also a decrease in the freezing point of its blood. (Anytime you add solute (antifreeze) to water, it decreases the freezing point of the solution.) 4. Insulation – to reduce heat exchange, you reduce the transfer of heat across the skin. Animals exposed to cold temperatures have a huge temperature difference (if they’re an endotherm) between their body temperature and the outside. Insulating is the major mechanism for reducing that heat loss. o EX: Animals on land, like wolves, need a heavy fur coat. Animals that swim in water, like seals, need blubber because when fur gets wet, it is no good. Animals like the polar bear have both because they live on land and water. They can swim for several days in the Arctic Ocean because they can maintain high metabolic activity in these harsh conditions. Their hair is transparent to allow the little sunlight of the arctic to reach their skin. Their skin is black to absorb that heat. o Adaptations to extreme heat: o Can be: Homeoviscous, Behavioral, Insulation, Heat Exchangers, Evaporative cooling, and Absorption of Water Vapor o Some of the same mechanisms occur as in animals exposed to extreme cold 1. Homeoviscous chemical adaptations occur at the biochemical level 2. Behavioral adaptations still occur o EX: Lizards’ burrow’s temperatures stay constant despite the outside temperature. In the morning, the lizard comes out of its burrow with a cold body temp, it then basks in the sun until its muscles are warm enough for it to go catch food, then when the body temp gets too high, it will sit under a rock until it cools down. During the day, the body temperature fluctuates a little throughout the day while going in and out of the sun. These lizards are ectotherms, so when it gets cold, their body temp cools down and they cannot move very fast. This is why they retreat to a burrow when it is cold. 3. Insulation – fur serves as insulation even in desert animals. o EX: The Arabian Oryx is the world desert champion. They can live for months without drinking liquid water. They get water from plants it eats and its metabolism. They have a heat exchanger in their circulatory supply to the brain. It is a system where veins surround arteries, providing countercurrent heat exchange. This allows the animal to keep its brain cooler. The nasal anatomy shows highly folded flaps of skin, nasal turbinates, which function like air conditioners. The animals breathe in hot, dry air, which evaporates water from the nose, and as this happens, the flaps of skin cool. The veins going through here are, as a result, cooler. It will breathe out moist, warm air, and water will condense on the turbinates. This conserves water and powers the brain’s cooling mechanism. 4. Heat Exchangers 5. Evaporative Cooling – using sweat glands to take heat away from the body as the water evaporates. Or panting. o EX: Animals that do not have sweat glands, like dogs, get rid of their body temperature by panting. This is moving air in and out of the upper respiratory passages. Hyperventilating to get more air to your lungs screws up the pH balance of your body because you loose lots of carbon dioxide. This is why dogs move air quickly in and out, but not into their lungs. There is a trade off between maintaining pH balance and cooling the body. 6. Absorption of Water Vapor – is possible in very few animals. Under certain conditions, they can absorb water vapor directly from the atmosphere. o EX: desert cockroaches have specialized mouthparts that have a dense mat of hydrofuse hairs that promote the condensation of water on the mouthpart. They can stick their mouthpart out in 70% humidity and water will condense on it. o EX: flower beetles take up water vapor from the air with a special organ. 1. On a hot summer day in the Australian outback, temperatures can reach 120° F; kangaroos urinate on their legs. 2. This reduces body heat by evaporative cooling. (A, A, related) • “The Ship of the Desert” – Camels o Camels exemplify the adaptations you find in animals that are highly adapted to desert environments. o EX: when a camel lies in the sun, it lays horizontally with its face pointing the sun to minimize the surface area exposed to the sun. The less surface area you have, the less heat energy you absorb. o A scientist tested the value of fur in camels by comparing the drinking rate of shaved and unshaved animals. He found that the shaved camels drank more than the unshaved animals. A shaved camel drinks 1.5 times more water. Fur insulates them and reduces the amount of heat energy they take in. (Energy coming into an animal depends on the surface area, the temperature difference of the body and outside, and the heat conduction of the skin.) Putting hair on skin reduces the thermal conductivity. o Camels show temporal heterothermy. Camels with access to water allow its body temperature to fluctuate a little, but a dehydrated camel will allow its body temperature to fluctuate more. As it’s hot in the day, the camel is hotter. As its cold at night, the camel is cooler. Why does it do this? A “heat budget” for camels shows that the camel without water’s body temperature is closer to that of the environment so it takes in less heat energy. So it has less heat to dissipate by evaporative cooling. A watered animal will dissipate a lot of heat by using its sweat glands because it can afford to lose water. By allowing its body temperature to fluctuate, the dehydrated animal reduces the amount of heat it takes in. o Kidney Function in Camels – the primary organ in maintaining salt/water balance is the kidney. Humans can concentrate their urine to about 3x the concentration of the blood plasma. Camels concentrate their urine 8x the concentration of the blood plasma. Some desert rodents can concentrate their urine to 12x. o Water loss in feces: Cows lose 75 g water/100 g poop. Camels only lose 44. Camels do anything to conserve water. o Dehydration in Humans vs. Camels: Camels can last weeks without water. Humans die when we lose 10% of our body weight. Camels can lose 50% of their body weight. They are more resistant to water loss. A dehydrated camel can drink 20 gallons of water in 5 minutes. The blood cells will swell because of all the osmosis that occurs. o Camel Red Blood Cells: animals in the camel family are the only mammals that have nucleated red blood cells because the nucleus allows the blood cells to be more resistant to osmotic shrinkage and swelling. They can tolerate swelling of 240% of normal volume. They are also oval-shaped so they can squeeze through capillaries even when the blood is super thick. ❖ ANIMALS: CIRCULATION o The components of a circulatory system are hemolymph, vessels, and pumps. o The function of a circulatory system is transport. It transports: 1. Gases – oxygen, carbon dioxide 2. Metabolites – sugars, amino acids 3. Signal molecules - hormones 4. Ions 5. Heat energy – (in endothermic animals) 6. Force – responsible for filtration and production of urine in the kidney by hydrostatic pressure o The blood pressure of a giraffe is very high because it has to pump blood all the way up its neck to the top of its head. • Circulatory Systems o There are 2 types of circulatory systems in animals: open & closed o Open circulatory systems: there is a major blood vessel with a few branches that come off that. There are no capillary beds connecting arterial circulation with venus circulation. There is a heart that pumps the hemolymph out of the main vessels that then mixes with the extracellular fluid. An animal with an open circulatory system’s circulating fluid is not separate from the extracellular fluid. This fluid is called hemolymph in animals with open systems. o Closed circulatory systems: there is a closed system of blood vessels with capillary beds connecting the arterial and venus vessels. The advantage of having a closed system is that by altering the blood flow through these capillaries, you can control the amount of blood flowing to different body parts. o EX: in vertebrates, all of the arterials leading into the capillary beds have a ring of vascular smooth muscle around that arterial. By adjusting contraction of this muscle, you can change the diameter of the blood vessel. • Components of Human Blood (from an animal with a closed circulatory system) o Plasma Portion 1. Mostly water 2. Plasma proteins 3. Ions, sugars, lipids, amino acids – things being transported by the circulatory system o Cellular Portion (formed elements) 1. Mostly red blood cells 2. White blood cells – involved in immune functions 3. Platelets – involved in clotting of the blood o Hematocrit is the proportion of red blood cells. It = vol. red blood cells/vol. whole blood. A typical human hematocrit is 40%. • All these blood cells originate from stem cells in the bone marrow. o Red blood cells (erythrocytes) carry oxygen o Platelets are involved in clotting o All other cells have immune functions • Regulation of Hematocrit: Negative Feedback o A hormone called Erythropoietin is produced in the kidney and is responsible for stimulating the production of more red blood cells. Oxygen deficiencies stimulate the release of this hormone to produce more red blood cells. o Athletes can cheat in athletic competition by blood doping. This is when some blood is removed and stored until game day, and then it is transfused back into the body, which increases oxygen supply to the muscles by raising their hematocrit. Another way to cheat is to inject erythropoietin into their blood. • Clotting – when a blood vessel is damaged, blood can leak out. The way to control this damage is: The smooth muscle surrounding that vessel constricts it, then platelets stick together to plug the hole, and there is a cascade of enzymes and plasma proteins that results in the formation of a fibrin network, which will trap more blood cells and platelets, and forms a blood clot. o Genes that are defective in producing some of these proteins results in the disease, Hemophilia, where blood will not clot. 1. Many people at risk for heart attacks take aspirin as a prophylactic to prevent blood clots in coronary arteries. 2. Aspirin makes platelets less sticky. (A, A, related) • The Human Circulatory System o There is a heart and major blood vessels and arteries leaving the heart. There are veins that bring blood back to the heart. There are capillaries connecting the veins and arteries. o Artery = red, warm, oxygenated blood = away from heart o Vein = blue, cooler, non-oxygenated blood = to the heart • Hearts o Hearts come in 2 kinds: 1. Neurogenic hearts – (in arthropods) the rhythmic contractions are initiated by pacemaker nerve cells, or neurons, in the cardiac ganglion, which is on the ventral side of the inside of the heart. 2. Myogenic hearts – (in humans and mollusks) rhythmic contraction of the heart is driven by modified muscle cells called pacemaker cells. They generate a regular electrical signal that causes other muscles in the heart to contract. • Mammalian Heart o The mammalian heart has 4 chambers – Right Atrium, Right Ventricle, Left Atrium, Left Ventricle, one-way valves connecting the atria and ventricles, valves that prevent back-flow of blood both in the pulmonary arteries and in the aorta. o This is a 4-chamber heart with 2 pumps working at the same time. The right side receives blood from the rest of the blood and sends it through the lungs to be oxygenated. The blood then moves into the left side and pumps it to the rest of the body. Pulmonary circulation involves the right side of the heart and the lungs. The systemic circulation involves the left side of the heart. The muscle on the left is much thicker than the right because the left side has to pump blood through more blood vessels and resistance to deliver it to places like the head and feet. The right side only has to deliver it to the lungs, so there is not much resistance. o Cardiac Muscle o is striated like skeletal muscle but the difference is that cardiac muscle cells tend to be branched and they have special junctions called intercalated disks which prevent the muscle cells from tearing apart when the heart fills with blood and contracts. o Heart Valves o Prevent backflow of blood. Leaky valves are called heart murmurs. Some diseases cause problems with the heart valves, like Rheumatic Fever or Stenosis, which causes the flaps of heart valves to become calcified and less flexible, which will prevent the heart valves from functioning properly. o Cardiac Cycle o When the heart is relaxed, it is called diastole. o Blood flows into the right side of the heart, then the atria contract and fill with blood to top off the ventricle, then ventricles contract which closes and opens new valves, leading blood into the lungs, then as the heart relaxes again, that blood enters the left atrium. o Electrocardiograms o There are 2 sets of pacemaker cells in the heart: one set in the sinoatrial node and one in the atrioventricular node. These cells generate electrical signals. When the heart contracts, all the muscle cells generate an action potential. The heart is a large organ, so this is a big enough electrical signal that it can be recorded with electrodes on your skin. o This is what electrocardiograms do. An EKG is the electrical activity of the heart. The graph has a P wave due to depolarization of the atria. The QRS complex is the ventricles contracting. The T wave is when the ventricles relaxing. The relaxation of the atria is masked by ventricular contraction. The shape of the waves allow cardiologist to assess where the damage is occurring in the heart or irregularities in the heartbeat. o Measuring Blood Pressure o Blood pressure can be monitored with a device called a sphygmomanometer. The average blood pressure is 120/80, Systolic/Diastolic, contracted/relaxed. o Called a sphygmomanometer, these devices usually include a pressure cuff. When it is inflated, it collapses the arteries in the arm, and no blood flow will be heard. When the pressure in the cuff = the systolic pressure the heart is generating as it contracts, it squirts blood through that artery and you can hear blood flow again. That point is the systolic pressure. You continue to release the pressure on the cuff and when the artery fills all the way with blood, you get a steady flow and that pressure is the diastolic pressure. o Pressure in the Circulatory System o There is a big decrease in blood pressure going from arteries  arterioles  capillaries  veins. Blood pressure is almost 0 in veins. So how does blood get back to the heart? By blood vessels o Blood Vessels o Veins vs. Arteries. Arteries must withstand the pressure pulse of the heart. They have a thick layer of connective tissue and smooth muscle. Veins are thinned walled with less of the pressure- withstanding mechanisms. o Blood flow can be controlled in a closed system by the smooth muscle in the arteries that can constrict a blood vessel and reduce the flow through. Veins have few layers of smooth muscle and connective tissue. Capillaries tend to have one cell layer and some have holes (like in kidney). o Blood flow through capillaries: red blood cells can squeeze through single file in some capillary beds. o Pressure relations in capillaries: There is high hydrostatic pressure on the arterial side (where water an solutes leave capillary), which draws water out of a blood vessel, and low hydrostatic pressure on the venule side (where water and solutes enter capillary). Water leaving makes the solute content higher on the venule side, but these forces are not equal. There is always a net loss of blood plasma into the extracellular fluid, then that leakage is taken up by the lymphatic system and is returned to the venule blood flow. o Venous return: one way that this venous return is enhanced is by the action of skeletal muscles and large veins. Veins with one-way valves work like this: as muscles work and squeeze the vein that drives blood back toward the heart, the blood cannot move backwards because of these valves. o EX: witting on an airplane for a while, your feet will swell because your blood vessels aren’t returning blood as quickly as they usually do. o EX: swelling in the legs due to a disease called Elephantiasis, which is caused by an infection of parasites that accumulate in the lymphatic vessels. 1. Blockage of the lymphatic vessels in the leg will cause swelling. 2. Blockage of the lymphatic vessels in the leg will cause blood clots. (T, F) *False because the components necessary to form a blood clot don’t leak out of a capillary. Only plasma leaks out of capillaries (not platelets and blood cells) • The Lymphatic System o Lymphatic vessels take in fluid that leaks from the capillary beds and have one-way valves. There are many white blood cells in lymph nodes that remove bacteria and other pathogens from your plasma as it flows through these lymphatic vessels. • Cardiovascular Disease o #1 killer for both men and women in America. o 30% of all 1 heart attack are fatal o Hypertension: (high blood pressure) can damage kidneys, causes heart to work harder. o Aneurisms: places in the blood vessels where connective tissue and smooth muscle surrounding the artery has become weak. A blood vessel can bulge and burst with internal bleeding. o Atherosclerosis: thickening of arteries due to plaque. Plaques are cause by excess cholesterol. They can occur at places where a blood clot is occurring. If this blood clot is in a coronary artery, it can lead to a heart attack. If the blood clot occurs in the brain, it leads to a stroke. o EX: if you eat too much boudin, it causes these plaques. They have a fat core and are very calcified. Excess cholesterol contributes to these. They narrow the diameter of the artery. Damage to a cap of this plaque causes serious problems. o What to do about these blockages in coronary arteries of the heart? A common procedure called Angioplasty, where they put a catheter in your leg and a tiny drill will grind plaque or a balloon will compress the fat out of the way. A more permanent fix is a wire. o Another option is coronary bypass surgery. If there is a blockage in the artery, surgeons can remove a piece of a large vein from the leg and graph it between the aortas and downstream of the blockage so blood can flow around the blockage. A triple bypass surgery is 3 of these graphs. ❖ Heart Attack Video • The man’s heart pumps enough blood to fill 40% each day. Red blood cells containing oxygen are pumped with amazing force. They provide oxygen to every muscle in the man’s body. The heart supplies itself with oxygen too. Coronary arteries feed blood to the walls of the heart. The walls are full of elastic muscle cells contracting together. • Inside a coronary artery is a ticking time bomb, a growth of cholesterol. Excess cholesterol seems into the blood and turns into a plaque, a fat-filled plaque. It will reduce the blood flow to his heart. We all have some plaques but this man has a lot and the blood is squeezed through vessels half the width they should be. • This man has advanced heart disease. A patch of his heart muscle became oxygen deprived. New muscles grew, like a natural heart bypass. This takes 2 days to grow, which is not fast enough to save John from what has happened. • The heart is the only organ with its own power supply. A natural pacemaker generates electrical pulses, which ensures the regular beat. Each pulse surges through the cells, causes everything to beat in unison. • When John becomes active, the heart needs to beat faster to supply his muscles with more oxygen. His brain sends a signal to the heart for more electrical pulses. It doubles his heart rate and he breathes faster to supply his hungry muscles with oxygen. John’s heart is working at its limit and putting him in danger. • The blood flows faster and faster, allowing more red blood cells to clot on the ripped open plaques in his coronary arteries. The flow of blood to John’s heart slows down and the heart’s oxygen supply dwindles. The heart sends pain signals to the brain and John doesn’t realize this is the start of a heart attack. • When the brain sends adrenaline through the bloodstream, and it arrives in his heart, it soaks into the walls. The pacemaker accelerates and his heart starts to accelerate, but the adrenaline can’t help the clot. It fills 90% of his artery and the supply of oxygen is almost nothing. They are forced to shut down the function, which absorbs most of his energy. • When the artery becomes completely blocked, the heart membranes do not have energy to hold together and the thin membranes start to leak. The lungs fill with liquid and John could drown in his own body fluid. The lack of oxygen affects John’s brain, making him dizzy. The starved muscle cells are beginning to die. The doctors use a drug to clear John’s artery soon enough before too many heart cells die and before he dies. • When one surviving cell beats out of sync, creating its own electricity, it throws the heart into chaos. The signal clashes with the pacemaker’s. The oxygen supply crashes to nothing. The electrical “clear” thingys jumpstart his heart back into beat. He’ll have to take blood-thinning pills for the rest of his life to prevent more clots. • Deaton’s correction on the video: in the initial formation of the clot, it would be platelets, not red blood cells. Risk factors for cardiovascular disease: overweight, smoking, stress, unhealthy diet, lack of exercise. Genetic factors like propensity toward cardiovascular disease, high blood pressure, etc. Angiogenesis is the growth of new blood cells. EX: John’s first problem made adjacent blood vessels grow new ways to the heart. This process is stimulated by exercise. ❖ ANIMALS: RESPIRATION (GAS EXCHANGE) • EX: At high altitudes, the bar headed goose flies at high altitudes. As you go up in altitude, gas pressure of the atmosphere decreases, so the partial pressure of oxygen decreases. Humans use oxygen tanks in high altitudes, but how do birds maintain vigorous exercise in high altitude conditions? • Not all animals have lungs or gills. Respiration does not have to happen in lungs only. Many organisms do not have a specific organ for gas exchange. EX: jellyfish, flatworm, and sponges. They use cutaneous gas exchange, that is, they take up oxygen from the water through their skin. Therefore, they rely on diffusion. Diffusion is slow and can only deliver oxygen in required amounts over a short distance. The tissues are close to the water so a lot of water can move past the tissues. (Skin has to be wet to dissolve gas. This works well for low metabolic activity (low O2 demand), usually in ectothermic animals. Aquatic animals must be thin because of the O2 availability in water. For most land animals, the portion of gas exchange that occurs cross the skin is very low.) o EX: Lungless salamanders do not have gas exchange organs. All O2 uptake is through their skin. They can only live in wet habitats. They like to stay under leaf littler and close to water. • Animals’ Oxygen Uptake from Air or Water o This process releases CO2 back to the environment. o Some animal’s breath air, while some breath water. These two media are very different. Our atmosphere is 19% O2. So there is a lot of oxygen in the air. Water, on the other hand, is 0.7% O2. The solubility of oxygen in water is low. This causes problems for aquatic animals. o As the temperature of the water increases, the solubility of O2 decreases and if you add solutes to the water, it decreases the solubility of O2. EX: Animals that live in tropical waters have much less available oxygen than animals that live in fast flowing freshwater. • Aquatic Respiration o As you add solute to water, it decreases the solubility of O2. o Increasing temperature or increasing salinity reduced solubility of gases. o Many aquatic animals can have internal gills or external gills o EX (external): Larval salamanders have external gills. Ventilation is moving the respiratory fluid past the cells of the gas exchange organ. Many animals pump water past their gills. They do not actively ventilate, which means you can get formation of unstirred layers around the gills. When the animal sits still, the water that passes through its gills has a low O2 content. These animals are not very efficient at extracting O2 from water, and as a consequence, they do not move quickly. 1. Ventilation of a gill with water costs more energy than ventilating a lung with air. 2. The gills of aquatic animals with high metabolic rates have very efficient oxygen extraction. (T, T, related) *What would you rather carry all day; a bucket of air or water?* o Animal living in water with a high metabolic rate. EX: Bluefin Tuna. What adaptations are present in its gas exchange organs compared to the salamander? o Fish Gills. Fish Gills have filaments. Gills have a lot of surface area. Water flow is opposite flow of blood. This is countercurrent blood flow. These fish have one-way/flow through ventilation: the fish open its mouth and takes in water and pushes it past the gills. So the gills are always exposed to high O2 water as the fish takes in a new mouthful of water. o Summary: fish ventilate their gills to prevent unstirred layers, they have a large surface area of gills, one-way ventilation, and countercurrent exchange of blood and O2. o The advantage of countercurrent exchange is that the O2 partial pressure in the blood is a little lower than the O2 partial pressure in the water. This means that the whole surface of the gill lamellae is functioning to take up water. o Mechanisms of Ventilation in Fish 1. Buccal pumping: used to ventilate their gills. It is mechanism that involves opening the mouth, lowering the jaw to draw water into the buccal cavity, then closing the mouth, raising the jaw, and forcing the water over the gills. 2. Ram ventilation: EX: Tunas. Some fish use this mechanism to forego wasting the energy of the jaw movement in buccal pumping. These fish swim through the water with their mouth open, which forces O2 past their gills. Tuna will suffocate if held still because they have to move to ventilate their gills. The efficiency of oxygen extraction in ram ventilators like tuna is pretty high. It approaches 90%, while human efficiency reaches only 10%. Although, it does not matter for us because there is so much O2 in the air that we can get along with poor O2 extraction. • Terrestrial Respiration o The O2 levels in the atmosphere are high to the partial pressure. 1 atm = 760 mm Hg at sea level. As you go up in altitude, that partial pressure decreases, therefore the O2 availability decreases. EX: On Mount Everest, the O2 availability is about half of what it is at sea level. o Terrestrial animals that breathe air’s problem is not how much oxygen is available, but it is losing water to the air that they bring into their lungs (desiccation). This is why land animals’ gas exchange organs are on the inside of their body cavity. Otherwise, they’d lose way too much water. The main problem of terrestrial animal gas exchange is loss of water by evaporation. o Insect (Terrestrial) Gas Exchange o Insect tracheal system is unique. It is a network of tubes that branch into finer and finer branches throughout the entire insect. These branches connect to the outside by spiracles that the animal can open and close. This is a way to reduce evaporative loss of water. Since this entire process works by diffusion, the circulatory system of an insect does not play a role in gas exchange. The tracheal system is part of the exoskeleton (made of chitin) that is shed during molts. (stopped this lecture to do sickle cell anemia video) ❖ Sickle Cell Anemia Video • Sickle Cell Anemia causes pain in its victims. Understanding sickle cell can tell us a lot about how the blood works. Sickle cell is a disease of the blood. How does Rose’s blood differ from healthy people’s? • Blood: cells suspended in a watery fluid called plasma. Plasma contains proteins, nutrients, and cells. There are 2 kinds of cells: white and red. White blood cells protect the body against disease. 95% of cells are red blood cells. They are very distinct, donut shaped, oxygenated, and no nucleus. • Rose’s blood: some cells are not donut shaped. These are the sickle cells that named the disease. How does this cause Rose’s pain? To understand the disease, we have to understand how blood circulates throughout the body. You have to start at the heart: • The heart: is 2 pumps working together. Each pump has 2 chambers. Blood enters the upper chamber, the atrium, and from there it is pumped through a valve into the lower chamber, the ventricle, the valve that closes so that the blood cannot flow back. From the ventricle, blood is pumped out of the heart (into the lungs). Process: Blood in the body is collected by veins and flows into the heart. It enters the right atrium. The heart contracts and the blood is forced through a valve into the right ventricle. Another contraction and the blood is pumped from the right ventricle, through the pulmonary artery, to the lungs. Here, the blood picks up O2. The new oxygenated blood then enters the left atrium in the heart. The atrium contracts and blood is forced into the left ventricle. From there it is pumped out of the heart, through the main artery, the aorta. This provides the entire body with oxygenated blood. • What does that tell us about sickle cell? Open-heart surgery shows how the blood works. Surgeons stop the heart while operating. A heart-lung machine replaces the functions of the heart and lungs. Tubes carry deoxygenated, darker red, blood away from the right side of the heart. To replace the lungs, oxygen, bright red, is passed through the blood. This color change is caused by the red blood cells picking up O2. If this were sickle cell blood, the cells would be deformed. What happens when O2 is bubbled through sickle cell blood? The cells return to their normal shape. • Rose’s pain comes from the cells changing shape. Her pain can be anywhere, depending on what activity she’s doing. Being cold, or doing strenuous activity all have the same affect on her blood; they slow down circulation and cause the red blood cells to lose oxygen more quickly. The problem occurs in the capillaries where oxygen is given to living tissues. Capillaries carry oxygenated blood to tissues through thin tubes. This is a tight squeeze through capillaries but the red blood cells are flexible. The red cells release oxygen when they are moving through the capillary, releasing it to surrounding tissues. Sickle cells look normal when they arrive in the capillary, but when their oxygen is released, they change shape, become less flexible, and cause blockage so other red blood cells cannot pass. This means no more oxygen supply. This causes pain and may cause permanent damage. • This sickle blood reduce/sickle crisis can happen anywhere there are capillaries, even affecting bones. Bone marrow can die, and bacteria can orient in these unhealthy bones and cause pain. Lungs can be sickled in, which sets up a vicious cycle of loss of oxygen in the lungs, therefore the entire body. • The red blood cells sickling and blockage circulation causes pain. But what makes the cell sickle? • Each blood cell contains thousand of molecule of the special protein, hemoglobin. Hemoglobin is a large protein molecule responsible for the transport of O2 in red blood cells. It is made up of 2 alpha units and 2 beta units. It holds the oxygen under these. These 4 heme groups look like a ring structure with an iron atom at the center. This is why you need iron to have healthy blood. In the lungs, where oxygen is plentiful, an oxygen molecule will attach to each heme group. This is the oxygen that will be carried in the blood and released to tissues. • Sickle cell hemoglobin’s only difference is in a small area. It is a change in one tiny molecule. The effect of this change is that the sickle cell hemoglobin molecule will form tiny threads, which makes a cell stiff and causes it to change shape. • Sickle cell is a genetic disease. Some are more susceptible to it. It is mainly in black people. • Deaton: sickle cell anemia is due to a recessive gene. You need 2 copies of the recessive gene to have the disease. Being heterozygous (1 copy) makes you a carrier of the disease. The difference in the hemoglobin is one amino acid difference. This disease is an example of stabilizing selection. The heterozygous form of the disease is maintained because it gives rise to resistance of Malaria. The spleen will detect cells affected by Malaria more readily. Malaria is hard to tackle because it lives in our own red blood cells. The immune system cannot destroy these molecules. Sickle Cell Anemia is more common in places where Malaria is more common like: Mediterranean Sea, Italy, North Africa, India, Africa, and Southeast Asia. (continuing gas exchange lecture) o Respiratory Organs of Terrestrial Animals Vary o EX: Land snail, pulmonate snail (pulmon=lungs), have lost gills that are typical in aquatic snails and instead have an opening into the body cavity called a pneumostome which allows the animal to open this hole, take in air, and provide the skin inside (which is richly supplied with blood vessels) with oxygen like a gas exchange organ. o EX: Book lungs in spiders have layers of thin tissues with lots of blood flowing through so the animals can take up oxygen. o These mechanisms are still inside the body cavity to reduce loss of water by evaporation. o EX: Frogs vs. Snakes. Frogs use their skin for gas exchange, so this restricts their choice of habitat and they must live in water. • Human Respiration o We have nasal cavity, airway to trachea, which splits to the bronchi and bronchial tubes, which supply air to alveoli (air sacs). There are 2 sets of muscles: muscles between the ribs are intercostal muscles. The flat muscle is the diaphragm, which separates the brachial cavity from organs below. o Lungs o Cleaning the airway: there is a lot of crap in the air. Breathing all this in will eventually coat your lungs. The cleaning mechanism consist of cells that line the epithelium that have goblet cells that secrete mucus and ciliated cells that move the mucus up out of your lungs into your mouth and then you swallow that mucus. This cleans the airway. A consequence of smoking is that it will eventually kill these cilia, making it almost impossible to clear all of the atmosphere’s crap in your lungs. o Bronchioles & Alveoli: Bronchiole tubes lead down to air sacs called alveoli. Air sacs are surrounded by capillaries to maximize the uptake of oxygen from the air inside the sac. There are smooth muscle fibers around the bronchiole tubes. When these smooth muscles squeeze down on the airway, it causes asthma attacks. The air sacs of the alveoli are a bunch of small air bubble. This creates more surface area. If it was one huge air bubble, it would collapse and you would be unable to re-inflate it. The epithelial cells produce protein surfactant molecules that reduce surface tension, which prevents collapse of your lungs. Infants do not have these surfactants, and premature babies often die because they have breathing problems and their lungs collapse. o Gas Exchange in an Alveoli: a blood vessel containing red blood cells takes up O2 and releases CO2. o Ventilation in the Human Lungs: We have tidal ventilation. During inhale, the diaphragm contracts (flattens) and the intercostal muscles contract, moving the rib cage up and out, creating a vacuum that pulls air into the lungs. During exhalation, the diaphragm relaxes, intercostal muscles relax, the rib cage moves down, and pushes air out. Inhalation is active. Exhalation is passive. • Bird Respiration o Birds have a lung with many air sacs attached to the airway. People hypothesized that these air sacs were accessory lungs. o Nielsen (camel dude) looked at birds as well. He wanted to know what the function of air sacs in birds was. EX: He used an ostrich. He stuck needles in the air sacs and sample the gases in the air sacs. He wanted to know how much O2 and CO2 were in the posterior and anterior air sacs. 1. If the CO2 content of the posterior air sacs is low, the air in them has not passed through the lungs. 2. If the CO2 content of the anterior air sacs is high, the air in them has not passed through the lungs. (F, F) 1. *If the air had passed through the lungs, the CO2 content would be high. 2. *? o The data of Neilson’s experiment showed: the posterior air sacs are high in O2 (this means the air in them has not gone through lungs, because the O2 content is the same as the outside air) and low in CO2. The anterior air sacs are low in O2 and high in CO2, (this means the air here has passed through the lungs). ((Ada tip): Air will be less oxygenated after it leaves the lungs because it gives it oxygen to red blood cells.) This creates a model of movement of air. It works like dis: When the bird inhales, air enters the nose and goes into the posterior air sacs. The bird exhales and the air sac contracts and pushes the air through the lung. The bird inhales again, the posterior air sac relaxes and that air moves from lungs to the anterior air sacs. When the bird exhales again, the air sacs contract and the air is pushed out. This means every time the bird ventilates, fresh air is going through the lungs. This is one-way ventilation. o The metabolic rate of birds is high. They have a large surface area to volume ratio because they are such small animals. Flight is very strenuous. Their blood flow is a mix of con-current and counter-current: crosscurrent. Blood flows opposite of air (like in fish gills, used to increase the efficient of oxygen extraction.) o Crosscurrent blood flow in bird lungs: 1. Convergent evolution is when organisms that are not closely related show the same adaptations to similar selection pressure. 2. The respiratory systems of birds and fish are an example of convergent evolution. (T, T, related) *EX: this is how bar headed goose can fly at high altitudes; they have a highly efficient respiratory system at extracting oxygen, just like fish. The adaptations like one-way ventilation, large surface area in gas exchange organs, countercurrent air/water to blood flow are similar. • Control of Ventilation in Terrestrial Animals o The ventilation rate of terrestrial animals is controlled by a set of neurons in the hindbrain called the respiratory center. These neurons send messages to the diaphragm and intercostal muscles to control both the rate of breathing and the depth of breathing. EX: running requires an increase in both. In terrestrial animals, this is controlled by changes in blood pH. When the muscles start working, it produces more metabolic CO2. Because CO2 dissolves in water, it will form carbonic acid; therefore, increase in CO2 in your body will lower your blood pH. Chemoreceptor cells in the blood vessels that monitor the pH of the blood. If the pH goes down, signals will be sent to increase your breathing rate (increases CO2). EX: holding your breath for a long period of time puts a person in respiratory acidosis. Eventually the neurons in the hindbrain will overrule the conscience control and make you inhale. Hyperventilating has the opposite effect, putting a person into respiratory alkalosis. The blood pH will increase because of the loss of CO2. Again, the neurons will eventually take over. • Respiratory Proteins o Hemoglobin’s primary function in animal blood is to increase the O2 carrying capacity of the blood. (Remember: the solubility of O2 in water is fairly low. So if you depend on blood to carry O2 to your tissues, it wont be very affective. Hemoglobin helps this out.) These proteins bind O2 reversibly so the O2 carrying capacity of blood will increase. Hemoglobin is found in vertebrates, annelid worms, mollusks, etc. o Hemocyanin is found in mollusks, arthropods. Instead of iron binding O2 (like Hemoglobin), this protein has copper. • Oxygen Binding Curve (shows how these proteins are involved in O2 transport) o These show the partial pressure of O2 vs. the % saturation of Hemoglobin (which means the % of heme units that are bound to an O2 molecule). o ‘P50’ is the partial pressure of O2 that saturates 50% of the Hemoglobin. This curve is S-shaped, due to cooperativity. Hemoglobin has 4 heme units, which are on the inside of the folded protein. When the first heme binds O2, it unfolds the Hemoglobin molecule, making it easier for other O2 molecules to reach the other heme units. That is why this binding curve’s slope grows then levels off when all 4 of the heme groups have bound O2. • The Bohr Effect (shows the effect of changes in pH on the binding of O2 and hemoglobin) o Under normal conditions, the P50 could be about 28. o If you reduce the pH by increasing the CO2 content (increases Co2 increases carbonic acid, which decreases pH), the curve shifts to the right, making the new pH about 35. This means the binding affinity of the O2 and the protein is lower (because it is taking a higher amount of O2 to cause the binding of the same amount (50%) of hemoglobin). o Many blood proteins show these Bohr shifts because if you have tissues that are metabolizing rapidly, they’re producing CO2. This is going to increase CO2, decrease pH, and the shift will curve to the right. This means that because the oxygen binding affinity has decreased, more oxygen is going to be released to those tissues from the hemoglobin. • Oxygen Binding Curve for Hemoglobin of Different Sized Animals o The smaller the animal, the further to the right the O2 binding curve is. This means that the hemoglobin has a lower affinity for binding O2. EX: At the same partial pressure of O2 (PO2), a mouse’s hemoglobin could be 60% saturated with O2, while an elephant’s could be 80% saturated with O2. o Mammals have venous reserves that store O2 in its blood incase the animal has to increase its metabolic rate. • CO2 Transport in Blood o Most CO2 is transported in the form of bicarbonate ions. o Process: the body tissues produce CO2 as a byproduct of metabolic activity. The CO2 diffuses into red blood cells. The enzyme carbonic anhydrase catalyzes the formation of bicarbonate, which then diffuses into the plasma. At the lung, the bicarbonate ion diffuses into a red blood cell. Carbonic anhydrase then converts bicarbonate to water and CO2. CO2 then leaves the lungs. o This is all driven by the partial pressure of CO2. If there is high CO2, the reaction ends at the lungs. If there is low CO2, the process begins at the lungs. 1. At high altitudes, the available oxygen is lower than at sea level. 2. The Hb (hemoglobin) of animals adapted to high elevations will have a lower oxygen affinity than animals from sea level. (T, F) • Respiratory Adaptions to High Altitudes o EX: Llamas live in high altitudes, and their Hb’s oxygen binding affinity is very high. Their oxygen-binding curve is much farther to the left than other mammals’. This is what you expect, because not much O2 is available. You need a good protein. • Human Respiration & High Altitude o Some peoples have lived at high altitudes for many years. There are many adaptations for these groups of people. o EX: Incan Indians and Tibetans live at high altitudes. Some things that occur to help these people are: they hyperventilate (higher rate of breathing), larger vital capacity (lungs take in more O2 with each breath), high hematocrit (have more red blood cells per unit volume of blood (this is just in Incans, which shows that the adaptations are not always the same)) • Air Breathing Divers o For a long time, people did not understand the physiology of these animals. o When these animals started to be understood, it was discovered that these animals would dive down for a period then come up for air for a period. o Sperm whales can dive about 1 mile, while penguins can dive 600 m. Some things sperm whales do when they dive: hyperventilate prior to dive, have lots of myoglobin (form of hemoglobin with one heme per molecule that has a high oxygen affinity; acts as an oxygen storage molecule found in muscle cells), have large blood volume (high hematocrit), blood distribution (they can control the flow of blood to certain body parts because they have a closed circulatory system. They send more blood to the brain and their swimming muscles.), they minimize their metabolism by sinking rather than swimming to save energy • How to Damage Your Gas Exchange Organs (Lungs) o Smoking causes buildup of lots of soot, and the lung volume to decrease. The alveoli in the lungs tend to collapse into one big bubble (this occurs in emphysema patients). o In emphysema patients, oxygen uptake and gas exchange is much less efficient. • How do Siamese fighting fish survive in a small bowl without an air pump? o The O2 availability of this water is low. The fish uses a lot of this oxygen, so the only oxygen coming in is what is diffusing in through the atmosphere through the tops of the bowl. o These fish stay alive by breathing air. They come up to the top of water and take in a mouthful of air. This how fish survive in stagnant water with low O2 availability. ❖ Secretariat (for funsiez) Circulatory System: • Secretariat: ran 1.5 miles in time 2:24. • His resting pulse was 30 beats/minute, and his racing pulse was 250 beats/minute; which shows that a larger animal has a lower pulse rate. (EX: hummingbird’s hearts beat 200 beats/minute) • When Secretariat was running at 40 mph, his pulse rate was way higher. • In a typical mammal, the heart is .3% of their body weight, while an average horse’s heart weighs 6 lbs. • Secretariat’s heart weighed 22 lbs., (in thoroughbred racehorses, a horse with an unusually large heart will be bread every once in a while and they turn out to be very good.) Respiratory System: • Our resting ventilation rate is about 7 breaths/minute. Secretariat’s resting ventilation rate was 10 breaths/minute and his racing ventilation rate was 150 breaths/minute. • All this combined with the circulatory data during racing shows that the horse is taking in a tremendous amount of oxygen. The heart is pumping blood through the body very fast. These animals are bred very close to the limit of how fast an animal could possibly run. ❖ Salt & Water Balance o EX: The Kangaroo Rat is a champion mammal at reducing the need for water. • Water: Inputs and Outputs o Animals take in water from food, drinking liquid water, producing water from your metabolism. (Remember: when we hydrolyze carbohydrates, it produces CO2 and metabolic water). In small animals, metabolic water is a major contribution to their needs. o Animals lose water by evaporative cooling, evaporation from the air they breathe, and in their urine and feces. o The inputs must equal the outputs for the animal to stay alive. Otherwise, it would dehydrate and die. • Osmotic Regulation in Fish o You have to think about what passive forces are moving water and ions in or out the body of the animal. If an animal has a net loss of water, it has to balance that by taking in more water. If it has a net gain of ions, it has to get rid of those ions somehow. o Freshwater Fish: o In a freshwater fish, the fish’s body fluids are much more concentrated with salt than the water it’s swimming in (the fish is hypertonic compared to its environment). This will cause the animal to gain water by osmosis. The fish will also lose ions by diffusion. o The fish has to make up for these passive movements by taking up ions from the water and get rid of the water it is gaining from osmosis. The fish does this this way: o Most freshwater fish do not drink a lot of water, so the gills pump NaCl into the animal against the concentration gradient, which requires an active transport mechanism. This requires the fish to expend lots of energy to take up ions. To get rid of the water, it produces a large volume of very dilute (unconcentrated) urine. o These characteristics are typical of all freshwater fish; they have some part of the body that actively transports ions in and they produce lots of urine with a low salt content. o Marine Fish: o In a marine fish, the fish’s body fluids are mu
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