Biology Exam 4 Notes

Biology Exam 4 Notes - Biology Exam 4 Notes Chapter 32...

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Chapter 32 Review (from book) What Are the Major Features and Functions of Circulatory Systems? Circulatory systems transport blood rich in dissolved nutrients and oxygen close to each cell, where nutrients can be released and wastes absorbed. All circulatory systems have three major parts: blood, a fluid; vessels, a systems of channels to conduct the blood; and one or more hearts that pump the blood. Invertebrates have open or closed circulatory systems. In open systems, blood is pumped by the heart into a hemocoel, where the blood directly bathes internal organs. Nearly all vertebrates have closed systems, in which the blood is confined to the heart and blood vessels. How Does the Vertebrate Heart Work? Vertebrate circulatory systems transport gases, hormones, and wastes; distribute nutrients; help regulate body temperature; and defend the body against disease. The vertebrate heart evolved from two chambers in fishes, to three in amphibians and most reptiles, to four in birds and mammals. In the four-chambered heart, blood is pumped separately to the lungs and through the body, maintaining complete separation of oxygenated and deoxygenated blood. Deoxygenated blood is collected from the body in the right atrium and passed to the right ventricle, which pumps it to the lungs. Oxygenated blood from the lungs enters the left atrium, passes to the left ventricle, and is pumped to the rest of the body. The cardiac cycle consists of two stages: (1) atrial contraction, followed by (2) ventricular contraction. The direction of blood flow is maintained by valves within the heart. The contractions of the heart are initiated and coordinated by the sinoatrial node, the heart’s pacemaker. Heart rate can be modified by the nervous system and by hormones such as epinephrine. What Is Blood? Blood is composed of both fluid and cellular materials. The fluid plasma consists of water that contains proteins, hormones, nutrients, gases, and wastes. Red blood cells, or erythrocytes, are packed with iron- containing called hemoglobin, which carries oxygen. Their numbers are regulated by the hormone erythropoietin. There are five types of white blood cells, or leukocytes, that fight infection. Platelets, which are fragments of megakaryocytes, are important for blood clotting. What Are the Types and Functions of Blood Vessels? Blood leaving the heart travels (in sequence) through arteries, arterioles, capillaries, venules, veins, and then back to the heart. Each vessel is specialized for its role. Elastic, muscular arteries help pump the blood. The thin-walled capillaries allow the exchange of material between the body cells and the blood. Veins provide a path of low resistance back to the heart, with one-way valves that maintain the direction of blood flow. The distribution of blood is regulated by the constriction and dilation of arterioles under the influence of the sympathetic nervous system and local factors such as the amount of carbon dioxide in the tissues. Local
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Biology Exam 4 Notes - Biology Exam 4 Notes Chapter 32...

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