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The circulatory system is great because we don’t have to rely on diffusion. Why is this a good thing? The circulatory system rapidly transports fluid in great quantities to the body allowing exchange of gasses, absorption of nutrients, and disposal of waste products by the cells with much greater efficiency. Math problem? Chapter 42 – Circulation and Gas Exchange If it takes 3 hours for a given quantity of glucose to diffuse 1 cm, how long would it take (in years) for that same quantity to move 2 meters (the approximate distance from your liver to your big toe)? The time it takes for a substance to diffuse form one place to another is proportional to the square of the distance. Multiply the square of the increase in distance (square the factor that the distance increased by and multiply that by the amount of time given for the previous diffusion distance). Math Problem – really it’s diffusion with the problem! Why again are they necessary? Gastrovascular Cavities – we know them well! Open circulatory system? It’s like a bellows! Bring on the hemolymph! Closed circulatory system That’s what you have – blood and tissues are separate. Which one is less costly in terms of energy? Types of Circulatory Systems Open and closed cardiovascular systems Different types of closed systems have been shaped by environmental factors The heart – mechanical pump consisting of two atria (receive blood) and two ventricles (pump blood to body). The vessels – arteries, veins, and capillaries (100,000Km is how many miles?). You also have arterioles and venules. We needed that four chambered heart and double circulation to deliver the energy needed for homeostasis – endotherms require a great deal of energy to sustain themselves. Vertebrate (and specifically mammal) cardiovascular systems Let’s follow Ms. RBC through the circulatory system. Below the sternum, the heart is about the size of your fist and is made mostly of cardiac muscle. The atria are thin walled and function mainly to collect blood returning to the heart (from where?). Ventricles are thicker and pump blood out to the pulmonary and systemic circulation. The Heart Thoughts about the pig heart dissection: Anterior and Posterior view of heart Different Chambers Find where the heart was cut by the butcher (anything missing?) ID Vessels – pulmonary artery, aorta, coronary arteries Semilunar and AV valves Muscle fibers Trace the path of blood flow Contraction (called systole) is the pumping of blood. Relaxation (called diastole) is the heart filling with blood. One complete contraction and relaxation is called the cardiac cycle. The volume of blood/minute that left ventricle pumps to the systemic circulation is the cardiac output. The heart is rhythmic. If not, you’re in trouble… The rate of contraction, or heart rate (heart beats/min and measured by taking your pulse) and stroke volume (amount of blood pumped by each ventricular contraction – averages 75mL). What is your cardiac output if your heart rate is 80 beats/min and your stroke volume equals the average? Many things can affect heart rate and stroke volume for better or worse. Cardiac output depends on two factors. How does your stamina (ability to sustain physical activity) increase with exercise? It has to do with an increased ability to get oxygen to your tissues. It turns out, the more you exercise, the thicker and stronger the muscle making up your ventricle becomes (as with any muscle – the myofibrils increase to increase muscle mass, not the number of cells). This increases the volume of blood the ventricles can pump with each contraction (called _______) Increased stroke volume means you body can decrease the other factor (called ______) that contributes to cardiac output. So Carmen asked me a question and my answer was lackluster. So I gave it some thought… We need the heart to maintain its rhythm or our tissues go without _______ and _________. We would also build up ________. Certain cardiac muscle cells are selfexcitable and have their own rhythm. When things function normally, the pacemaker of the heart excites all other cardiac cells. How the heart maintains it’s beat… Let’s see how impulses are conducted through the heart. Nervous system Hormones Temperature Exercise What’s are ECGs and AEDs? What affects heart rate? Arteries, Veins, and capillaries (arterioles and venules, too). Arteries are thicker because they move blood rapidly under higher pressures. Veins have valves and take advantage of muscle movement. Capillaries are thin. All are lined with endothelium. Which ones carry oxygenated blood? http://www.biosbcc.net/doohan/sample/h tm/vessels.htm Da pipes… When you build up muscle, do you make new capillaries to accommodate the increase muscle size. The answer is yes, which is surprising, because in most instances we don’t. Blood vessels grow to line the uterus each month and new vessels grow in the process of repairing a wound. Turns out exercise causes chemicals to be released that stimulate vessel growth when muscle mass increases. Then Anthony asked me a question… The majority of the 100,000km of vessels in your body are capillaries. If volume per minute is constant, velocity of fluid will increase when diameter decreases If total diameter of the pipe determines velocity, why does blood slow down in the capillaries? Why is this good? Blood velocity and pressure in the cardiovascular system. Force exerted by blood on walls of vessels Blood pressure is pressure on arteries during contraction – systolic pressure and relaxation – diastolic pressure). Blood enters arteries faster than it can leave and the arteries stretch. You can feel your pulse and take your blood pressure because of arterioles. Arterioles cause peripheral resistance. Pressure, coming down on me… Peripheral resistance and cardiac output play off each other to maintain appropriate pressure. As blood pressure decreases, cardiac output (pulse x stroke volume) increase and vice versa. Position, exercise, hormones, nerve signals, and other factors affect blood pressure. Blood pressure is a team effort. What’s up with this? Lymphatic system has capillaries intertwined with blood capillaries to catch excess fluid and protein that would otherwise be lost after leaving the blood capillaries. Dumps back into circulatory system into the vena cava near the right atrium. Lymph capillaries to lymphatic vessels passing lymph nodes along the way. Lymph Several cell types are suspended in a liquid matrix called plasma. Mostly water, but also contains ions for osmotic balance and to help buffer the blood. Cells in the blood include erythrocytes (RBCs), leukocytes (WBCs – several different kinds) and platelets (chunks of cells that help with clotting). Cellular elements don’t last forever. Thank the Good Russo for pluripotent stem cells in red marrow of bones. Blood Negative Feedback involves a set point. In the case of RBC production, the set point is for _____ in the blood. Low O2 getting to tissues, kidneys release _____, stimulating production of _________. What happens if the tissues get more than they need. What does this get us back to? Naughty, naughty! Homeostasis! Fibrinogen to fibrin…thanks _______! It’s positive feedback because there’s no _____________. What’s hemophilia? Positive feedback – we are so lucky to have an example of each in the same chapter! Heart attack Stroke Atherosclerosis (plaque builds up) Arteriosclerosis (hardening of the arteries) Hypertension LDLs (bad) and HDLs (good) What lifestyle choices will you make (are you heart smart or heart stupid?). It feels like an elephant is sitting on my chest. Exchange gas with what? How do we exchange gas or perform respiration (don’t confuse with cellular respiration)? What are the two respiratory mediums? What happens at an animal’s respiratory surface? How does water play a role regardless of the terrestrial or aquatic nature of the animal? Why do endotherms have a larger surface area for gas exchange? How do you expel…oh, oh, I mean exchange…gas? The majority of cells that make up an animal usually don’t have direct access to a respiratory medium. Fish use gills Insects use tracheal systems – tubes that deliver air directly to body cells. We (mammals, birds, reptiles, and amphibians, spiders, and snails) use lungs. Some also exchange through skin – these animals must live in moist environments. What is ventilation? Where it starts! Let’s follow an O2 molecule through the respiratory system. Here’s a real larynx! Here’s the alveoli! Positive and negative pressure breathing Lung volume increase when intercostal (rib) muscles and the diaphragm contract. Other muscles help when you are really working. The volume of air that goes in and out is your tidal volume and the max is your vital capacity. Don’t smoke unless you want more residual air lurking in your lungs. Again, what creates the negative pressure? What influences the breathing centers? CO2 levels. But how? Once CO2 dissolves into the CSF, what happens? How is the pH of CSF affected by CO2? Jim Newman, you fool! Why you shouldn’t chase the dragon… A gas always diffuses from a region of higher partial pressure to a region of lower partial pressure…oh wait, what’s partial pressure? CO2 has a higher partial pressure in lungs than atmosphere and its just the opposite for O2…oh goody! Know your hemoglobin…and who cares if elephant seal can dive down over a mile and hold their breath for two hours! Thank goodness for partial pressure