John A. Ferguson Senior High School



BENCHMARK SC.912.L.14.36Describe the factors affecting blood flow through the cardiovascular system.Students will identify factors that affect blood flow and/or describe how these factors affect blood flow through the cardiovascularsystem.Items may address factors such as blood pressure, blood volume,resistance, disease, shape, and exercise.DiseaseA healthy cardiovascular system is very important to maintain good health. Failing to maintain good cardiovascular health can result in heart disease or atherosclerosis. In atherosclerosis, cholesterol, fatty substances, calcium, and other substances start to build up in the inner lining of an artery. This buildup, called plaque, leads to a narrowing (smaller diameter) of the artery. If a plaque breaks, it can cause a blood clot to start. A blood clot can block blood flow or can travel to a different part of the body. Depending on where the clot occurs, it can cause a heart attack or a stroke. A heart attack or stroke is a very dangerous health problem, but even plaque that stays put can cause issues by contributing to poor blood flow. Poor blood flow can cause chest pains, high blood pressure, shortness of breath during light exercise, leg pain, and loss of oxygen to the brain.Blood PressureThe blood pressure in the circulation is principally due to the pumping action of the heart.[2] Differences in mean blood pressure are responsible for blood flow from one location to another in the circulation. Arteries become less flexible.ResistanceA high viscosity of blood causes an increased resistance in the blood vessels and leads toslow blood flow.The rate of mean blood flow depends on the resistance to flow presented by the blood vessels. Mean blood pressure decreases as the circulating blood moves away from the heart through arteries, capillaries and veins due to viscous losses of energy. Mean blood pressure drops over the whole circulation, although most of the fall occurs along the small arteries and arterioles.[3] GravityGravity affects blood pressure via hydrostatic forces (e.g. during standing) and valves in veins, breathing, and pumping from contraction of skeletal muscles also influence blood pressure in veinsExerciseWe breath in more oxygen and we have to respire quickly. Our heart has to pump the oxygenated blood around our body faster and take the deoxygenated blood to the lungs to get the carbon dioxide out. 180/90 blood pressure while doing exerciseBlood VolumeBlood volume is the volume of blood (both red blood cells and plasma) in the circulatory system of any individual. Determines the viscosity of the blood.Things to Ponder Blood FlowBlood PressureResistanceExtra NotesGravityLow+─Laying in bed, high altitudesGravityHigh─+Standing, dehydration, divingViscosityLow +─Viscosity High ─+Vomiting,Diseaseatherosclerosis─+Heart diseaseBlood VolumeHigh─+Blood VolumeLow──DehydrationCell ShapeNormal cellnormalnormalCell ShapeAbnormal sickle ─+Any abnormal shape causes resistance and high Blood pressureExercise++Increase pressure does not increase blood flowIncrease blood volume does not increase blood flowIncrease resistance does not increase blood flowExercise increases resistance, pressure, and blood volumeHigh Viscosity increases resistanceThe rate at which blood flows through the human body changes in response to many factors.Which statement describes one of these factors and its effect on blood flow?A. A high viscosity of blood causes an increased resistance in the blood vessels and leads to slow blood flow.B. A low blood pH decreases the rate of diffusion through the blood vessels and leads toslow blood flow.C. The changing of the shape of red blood cells to a crescent shape decreases resistance and leads to a faster blood flow.D. The narrowing of blood vessels increases pressure and leads to a faster blood flow. ................
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