12_H14_CO_Flow_BP1 - CH 14 Cardiac Output, Blood Flow, and...

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Unformatted text preview: CH 14 Cardiac Output, Blood Flow, and Blood Pressure Cardiac Output Regulation of cardiac rate Regulation of Stroke Volume Venous return Blood & Body Fluid Volumes Exchange of Fluid Between Capillaries and Tissues Regulation of Blood Volume by the Kidneys Factors Affecting Blood Flow Vascular Resistance to Blood Flow Physical Laws Describing Blood Flow Extrinsic Regulation of Blood Flow Regulation of Blood Flow Through Skeletal Muscles Circulatory Changes During Exercise Blood Flow to the Heart and Skeletal Muscles Blood Flow to the Brain and Skin Blood Pressure Hypertension, Shock, and Congestive Heart Failure Volume of blood pumped/min by each ventricle. CO = SV x HR Stroke volume (SV) = blood pumped/beat by each ventricle Total blood volume is about 5.5L Cardiac Output (CO) Regulation of Cardiac Rate SAN pacemaker establishes baseline heart rate; ANS & hormones modify it. Autonomic nerves to the SAN are main controllers of heart rate. Sympathetic & parasympathetic nerves change heart rate (a chronotropic effect) by modifying rate of spontaneous depolarization of SAN. Fig 13.18: Pacemaker potentials and action potentials in the SA node. action potential SA Node Pacemaker Regulation of Cardiac Rate RATE INCREASES NO R & Epine phrine s tim ula te o pe ning o f pa c e m a ke r HC N c ha nne ls c a us ing fa s te r Na + influx. This de po la rize s S AN fa s te r, & inc re a s e s he a rt ra te . RATE DECREASES ACh opens K + channels. The resultant K+ outflow counters the Na+ influx; this slows depolarization & decreases heart rate. Fig 14.1 Fig 14.1 Base rate Nor/Epi: Increased rate ACh: decreased rate Cardiac control center in medulla oblongata coordinates activity of autonomic nerves. Sympathetic nerves to atria & ventricles stimulate increased strength of contraction (inotropic effect). Regulation of Cardiac Rate continued Stroke Volume (CO = SV x HBR) SV determined by 3 variables: 1.Contractility (strength of contraction); 2.Preload: amount of blood in the heart just before contraction (EDV); 3.Afterload: mean arterial pressure (total peripheral resistance, TPR) slows ejection from ventricle. SV is dire c tly pro po rtio na l to : (1) Strength of contraction which va rie s dire c tly with EDV (stretching): i nc re a s e c o ntra c tility, inc re a s e S V; (2) Preload : inc re a s e pre lo a d, inc re a s e S V) Ejection fraction = SV/ EDV....
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This note was uploaded on 02/12/2012 for the course BI 202 taught by Professor Winn during the Fall '10 term at Northern Michigan University.

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12_H14_CO_Flow_BP1 - CH 14 Cardiac Output, Blood Flow, and...

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