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Chapter 13 The Cardiovascular System Cardiac Function (Extended Notes)
Human Physiology (GNUR156)
Loyola University Chicago
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Term 2Preview text
Chapter 13 → The Cardiovascular
System: Cardiac Function (Extended
Notes)
3 overview of the cardiovascular system the heart blood vessels blood transport of substances O2 and nutrients to cell wastes from cells to liver and kidneys hormones, immune cells, and clotting proteins to specific target cells
blood vessels
vasculature arteries → large, branching vessels taking blood away from the heart arterioles → small branching vessels with high resistance capillaries → site of exchange between blood and tissue venules → small converging vessels veins → relatively large converging vessels that conduct blood to the heart CLOSED SYSTEM blood erythrocytes → red blood cells transport O2 and CO leukocytes → white blood cells defend body against pathogens platelets → cell fragments importation in blood clotting plasma → fluid and solutes 13 the path of blood flow through the heart and vasculature series flow through the cardiovascular system parallel flow within the systemic or pulmonary circuit series flow through the cardiovascular system pulmonary circuit supplied by right heart blood vessels from heart to lungs and from lungs to heart systemic circuit supplied by left heart
parallel blood flow within the systemic or pulmonary circuit aorta → arteries → arterioles → capillaries oxygenated blood enters each capillary bed parallel flow allows independent regulation of blood flow to organs capillaries → venules → veins
coronary circulation parallel with other organs in the systemic circuit blood in chambers does not suply nutrients to cardiac cells heart has its own set of capillaries heart capillaries are supplied by coronary arteries (left & right) that arise from the aorta
endothelium → inner layer of endothelial cells
valves and unidirectional blood flow pressure within chambers of the heart varies with heartbeat cycle pressure difference drives blood flow high pressure to low pressure normal direction of flow atria to ventricles ventricles to arteries valves prevent backward flow of blood all valves open passively based on pressure gradient artoventricular (AV) valves right AV valve = tricuspid valve left AV valve = bicuspid valve = mitral valve papillary muscles and chordae tendinae
keep AV valve from everting semilunar valves aortic valve pulmonary valve
13 electrical activity of the heart the conduction system of the heart spread of excitation through the heart muscle ionic basis of electrical activity in the heart electrical activity in cardiac contractile cells
cardiac cells are linked by gap junctions fastest depolarizing cells control other cells fastest cells = pacemaker = set rate for rest of heart action potentials per minute spread of excitation between cells atria contract, then ventricles contract coordination due to presence of gap junctions and conduction pathways intercalated disks junctions between adjacent myocardial cells desmosomes to resist mechanical stress gap junctions for electrical coupling
the conduction system of the heart initation and conduction of an impulse 1. AP initated in SA node; signals spread through atrial muscle via interatrical pathways 2. signal travels to AV node via internodal pathway; AV nodal delay 3. atrioventricular bundle (bundle of His)
- splits into left and right bundle branches
- purkinje fibers
spread of excitation through the heart muscle interatrial pathway SA node → right atrium → left atrium internodal pathway SA node → AV node AV node transmission only pathway from atria to ventricles slow conduction: AV nodal delay = 0 sec atria contract before ventricles ventricular excitation
repolarization open K+ channels
ionic basis of electrical activity in the heart 5 phases of electrical activity in cardiac contractile cells phase 0 = increased permeability to Na+ phase 1 = decreased permeability to Na+ phase 2 = increased permeability to ca2+ decreased permeability to K+
phase 3 = increased permeability to K+ decreased permeability to Ca2+ phase 4 = resting membrane potential cardiac contractile cell action potential long duration = 250-300 msec skeletal muscle = 1-2 msec
ionic basis of electrical activity in the heart excitation-contraction coupling in cardiac contractile cells properties similar to skeletal muscle
ionic basis of electrical activity in the heart relaxation of cardiac muscle removes calcium from cytosol Ca2+ ATPase in sacroplasmic reticulum Ca2+ ATPase in plasma membrane Na+ - Ca2+ exchanger in plasma membrane troponin and tropomyosin return to their positions covering myosin → binding sites on actin Recording the Electrical Activity of the Heart with an Electrocardiogram Can be recorded from electrodes on the skin Noninvasive technique Used to test for clinical abnormalities related to conduction of electrical signals in the heart Electrocardiogram → external measure of electrical activity of the heart Body = conductor Currents in body can spread to surface (ECG, EMG,EEG Distance and amplitude of spread depend on two factors size of potentials synchronicity of potentials from other cells Heart electrical activity—synchronize
Recording the Electrical Activity of the Heartwith an Electrocardiogram electrical activity of heart P wave → atrial depolarization QRS complex → ventricular depolarization and atrial repolarization T wave → ventricular repolarization PQ segment → ventricular systole QT interval → ventricular diastole figure 13 electrical activity of the heart
results in an extra systole permature atrial contraction (PAC), followed by an extra ventricular contraction ventricular fibrillation loss of coordination of electrical activity of heart death can ensue within minutes unless corrected figure 13 lead II ECGs showing various arrhythmias
13 the cardiac cycle phases of the cardiac cycle artial and ventricular pressure aortic pressure
Chapter 13 The Cardiovascular System Cardiac Function (Extended Notes)
Course: Human Physiology (GNUR156)
University: Loyola University Chicago
- Discover more from:
Students also viewed
- Chapter 20 The Gastrointestinal System
- Chapter 19 The Urinary System Fluid Electrolyte Balance
- Chapter 16 The Respiratory System Pulmonary Ventilation
- Chapter 15 The Cardiovascular System Blood
- Chapter 14 The Cardiovascular System Blood Vessels Blood Flow and Blood Pressure
- Chapter 12 Muscle Physiology (Extended Notes)
Related documents
- Chapter 11 The Nervous System Autonomic and Motor Systems (Extended Notes)
- Chapter 10 The Nervous System Sensory Systems
- Chapter 9 The Nervous System Central Nervous System
- Chapter 8 Synaptic Transmission and Neural integration
- Chapter 7 Nerve Cells and Electrical Signaling
- Chapter 4 Cell Membrane Transport