Acute rheumatic fever Mitral stenosis -- Accentuated first sound Mitral stenosis – Presystolic murmur Mitral regurgitation -- systolic murmur Aortic insufficiency -- Loud systolic ejection murmur, third sound
Mechanical Events of the Cardiac Cycle
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Flash Animation
Summary of events in the left atrium, left ventricle, and aorta during the cardiac cycle
Cardiovascular Physiology
（心血管生理学）
Excitation-Contraction Coupling In Cardiac Muscle
The mechanism that couples excitation – an action potential in the plasma membrane of the muscle cell – and contraction of heart muscle
calcium ions released into the cytosol bind to troponin.
The calcium-troponin complex “pulls” tropomyosin off the myosin-binding site of actin, thus allowing the binding of the cross-bridge, followed by its flexing to slide the actin filament.
RIS--right intercostal space LIS—left intercostal space ICS--intercostal space LLSB--left lower sternal border
（心音图）
Heart valve defects causing turbulent blood flow and murmurs
Excitation-contraction coupling in cardiac muscle
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Flash Animation
Cardiac cycle（心动周期）
• The cardiac events that occur from beginning of one heartbeat to the beginning of the next are called the cardiac cycle
Excitation-contraction coupling in skeletal muscle
Calcium ions regulate the contraction of cardiac muscle:
the entry of extracellular calcium ions causes the release of calcium from the sarcoplasmic reticulum (calcium-induced calcium release [钙诱导的钙释放]), the source of about 95% of the calcium in the cytosol.
What happens in the heart during each cardiac cycle?
• Pressure • Volume • Valves • Blood flow
Systole: ventricles contracting
Diastole: ventricles relaxed
Pressure changes in the right heart during a contraction cycle.
Role of atria and ventricles during each cardiac cycle
• Atria──primer pump • Ventricles──major source of power
Chest surface areas for auscultation of normal heart sounds
Four traditional value areas – Aortic space: 2RIS – Pulmonic valve: 2LIS – Tricuspid valve: 4ICS LLSB – Mitral valve: Apex
Passage of an action potential along the transverse tubule opens nearby voltage-gated calcium channels, the “ryanodine receptor,” located on the sarcoplasmic reticulum, and
Heart Sounds
• 1st sound – soft low-pitched lub – associated with closure of the AV valves – Marks the onset of systole
• 2nd sound – louder dup – associated with closure of the PA and aortic valves – Occurs at the onset of diastole