biol_119_lecture_10_9-23-09

biol_119_lecture_10_9-23-09 - Exchange of oxygen and carbon...

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Exchange of oxygen and carbon dioxide between blood and respiring tissues occurs across the walls of A. Arteries B. Veins C . Capillary beds D. Arterioles E. Venules
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C. Maintaining the Heart’s Rhythmic Beat Because the timely delivery of oxygen to the body’s organs is critical for survival, several mechanisms have evolved that assure the continuity and control of heartbeat. Certain cells of vertebrate cardiac muscle are self-excitable, meaning they contract without any signal from the nervous system. Each cell has its own intrinsic contraction rhythm. However, these cells are synchronized by the sinoatrial (SA) node, or pacemaker, which sets the rate and timing at which all cardiac muscle cells contract. The SA node is located in the wall of the right atrium (next slide, and figure 42.9). The nervous system (sympathic and parasympathic), hormones and body temperature can also affect heart rate
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The control of heart rhythm A region of the heart called the sinoatrial (SA) node, or pacemaker sets the rate and timing at which all cardiac muscle cells contract Impulses from the SA node travel to the atrioventricular (AV) node At the AV node, the impulses are delayed and then travel down the Bundle of His to the Purkinje fibers that make the ventricles contract Figure 42.9 SA node (pacemaker) AV node Bundle branches Heart apex Purkinje fibers 2 Signals are delayed at AV node. 1 Pacemaker generates wave of signals to contract. 3 Signals pass to heart apex. 4 Signals spread Throughout ventricles. ECG •The impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG)
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Concept 42.3: Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels The same physical principles that govern the movement of water in plumbing systems also influence the functioning of animal circulatory systems
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A. Blood Vessel Structure and Function The “infrastructure” of the circulatory system is its network of blood vessels (Figure 42.10) All blood vessels Are built of similar tissues Have three similar layers On the outside , a layer of connective tissue with elastic fibers allows the vessel to stretch and recoil. A middle layer has smooth muscle and more elastic fibers . Lining the lumen of all blood vessels, including capillaries, is an endothelium , a single layer of flattened cells that minimizes resistance to blood flow.
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B. Blood Flow Velocity Within the body, the most surface area is in the capillaries. The velocity is fastest in the arteries >veins >capillaries (The resulting slow flow rate in the capillaries and the thin capillary walls enhance the exchange of substances between the blood and interstitial fluid. Pressure is greatest in
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This note was uploaded on 05/04/2011 for the course BIO 119 taught by Professor O'donnellandspear during the Spring '07 term at SUNY Geneseo.

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biol_119_lecture_10_9-23-09 - Exchange of oxygen and carbon...

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