Lecture 29 Intro to Physiology and the Circulatory System Understand that diffusion is the major mechanism for the movement of substances in organisms that diffusion rate is a function of surface area and the distance over which diffusion must occur That a circulatory system is required for delivery of nutrients and removal of wastes whenever cells are more than 1 mm from an external surface o Diffusion is a major mechanism for the movement of chemicals in a liquid surrounding organisms and inside of organisms o Rate of Diffusion area x concentration gradient distance o Effective diffusion distance for organisms is or equal to 1 mm Know the difference in structure between open and closed circulatory systems Know the meaning of the terms hemolymph interstitial fluid and blood o Large multicellular animals rely on pumping systems to deliver nutrients and take away wastes Circulatory system delivers nutrients to all the cells and removes wastes Respiratory system uptake of oxygen and excretion of CO2 o Circulatory system is composed of the heart blood vessels and blood or hemolymph o Closed circulatory systems have the blood closed at all times within vessels of different size and wall thickness In this type of system blood is pumped by a heart through vessels and does not normally fill body cavities In short blood is completely enclosed in blood vessels capillaries o Open circulatory systems pump blood into a hemocoel primary body cavity of most invertebrates with the blood diffusing back to the circulatory system between cells Blood is pumped by a heart into the body cavities where tissues are surrounded by the blood In short with absorbed Cavity is filled blood and gets back into the heart through open ended pores there are no blood vessels transporting the blood o Hemolymph occupies the hemocoel the combination of interstitial fluid and blood in invertebrates o Interstitial fluid a solution that bathes and surrounds the cells of multicellular animals It is the main component of the extracellular fluid which also includes plasma and transcellular fluid o Blood red liquid that circulates in the arteries and veins of humans and other vertebrate animals carrying oxygen to and carbon dioxide from the tissues of the body Know that transport in the vertebrate circulatory system is pressure driven and understand the relationship between flow rate pressure and resistance o Pumping depends on hydrostatic pressure o Water is an incompressible fluid when pressure is applied to it a hydrostatic pressure results o Water flows from regions of high pressure to lower pressure regions o Blood flow rate change in pressure between two points resistance o Resistance increases with decreasing diameter of vessels As vessels get smaller the resistance of blood flow increases because its harder to get through Know the organization of the circulatory systems with two three and four chambered hearts which vertebrate groups have which and how the three and the four chambered hearts increased efficiency of the circulatory system o Two chambers atrium ventricle Fish Blood flows unidirectional from the two chambered heart through the gills and then to the rest of the body o Three chambers left and right atrium one ventricle Amphibians Reptiles Two circulatory routes one for oxygenation of the blood through the lungs and skin and the other to take oxygen to the rest of the body Blood is oxygenated through the lungs The heart is three chambered but the ventricles are partially separated so some mixing of oxygenated and deoxygenated blood occurs except in crocodilians and birds o Four chambers two atria and two ventricles Mammals Completely separate the oxygenated and deoxygenated blood it pumps only oxygenated blood through the body and deoxygenated blood to the lungs o The number of heart chambers atria and ventricles moderate the amount of mixing of oxygenated and deoxygenated blood in the heart as more chambers mean more separation between the systemic and pulmonary circuits The three and four chambered hearts increase efficiency because the oxygenated blood completely separated from the deoxygenated blood Know the parts of the mammalian heart and the pattern of blood flow in our circulatory system Know the contraction pattern and be able to correctly use the terms diastole and systole Know the function of the sinoatrial node pacemaker region and the AV atrioventricular node in controlling heart contraction o The heart has valves to prevent the backflow of blood between contractions o Diastole relaxation o Systole contraction o Sinoatrial SA node function impulses and then sending electrical signals through the heart muscle causing the heart to contract and pump blood throughout the body Controls the heart rate by generating electrical o Atrioventricular AV node function takes the signal from the SA node slows the signal down and regulates it and then sends the electrical impulses from the atria to the ventricles The AV node regulates the signals to the ventricles to prevent rapid conduction atrial fibrillation as well as making sure that the atria are fully contracted empty and closed before stimulating the ventricles Know the differences in structure between arteries and veins the difference in hydrostatic pressure in arteries and veins and the mechanism of blood flow in the veins o Arteries pump blood out under high pressure Arteries have narrow diameters and thick muscular walls carry the blood under high pressure to the capillaries o Veins return blood under low pressure Veins are larger in diameter carry blood under low pressure and have valves to prevent backflow o Flow is pressure driven Flow of blood is regulated in response to the demands of the body for oxygen Sphincters in the capillary beds open and close depending on where oxygen is needed changing the blood flow to that place Understand the mechanism of fluid transfer between the capillaries and our body tissues Fluid flows out from the capillaries and back in from the tissues o Capillary branching blood vessels that form a connection between the arterioles and venules They are the sites of the transfer of oxygen and other nutrients from the bloodstream to the other tissues in the body o Nutrients transferred from the blood to the interstitial fluid are pressure driven o Fluid moves between the cells lining the capillary Cells and proteins are held back in the blood o Blood pumps from the arteries into the capillary bed The pressure causes
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