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Final Exam 4.2.8-5.2.1.docx

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Anatomy and Physiology
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428Cardiac CycleoSystole the periods of contractionoDiastole the periods of relaxationoCardiac Cycle includes all the events associated with the blood flow through the heart during one complete heart beat atrial systole and diastole followed by ventricle systole and diastoleMarked by a succession of pressure and blood volume changesThe starting point is an arbitrary one since blood flows continuouslyoVentricular filline mid to late diastolePressure in the heart is lowBlood returning to the heart is flowing passively through the atria and the open AV valves into the ventricleAortic and pulmonary valves are closedMore than 80 of ventricular filling occurs during this periodFollowing depolarization p phase of the ECG the atria contracts compressing the bloodThis cause a slight rise in atrial pressure which propels the remaining 20 of residual blood out of the atria and into the ventricleVentricles are at the last stage of diastole and contain the maximum amount of blood This is called end diastolic volume EDVThe atria relaxes and the ventricle depolarizes QRS complexAtrial diastole persists through the rest of the cycleoVentricular systole atria in diastoleventricles walls close in on the blood and ventricular pressure rises rapidly and sharply closing the AV valvesDuring the split second when the ventricles are completely closed chambers and the blood volume in the chambers remains constantAs the ventricles contractit is known as the isovolumetric contraction phaseVentricular pressure continues to riseWhen it finally exceeds the pressure in the large arteries issuing from the ventricles the isovolumetric stage ends The SL semilunar valves are forced open and blood rushes from the ventricles into the aorta and pulmonary trunkThe pressure of the aorta normally reaches 120 mmHg during this stageoIsometric relaxation early diastoleBrief stage following the T wave the ventricles are relaxedThe blood remaining in their chambers end systolic volme ESV is no longer compressedVentricle pressure drops rapidly and blood in the aorta and pulmonary trunk flows back toward the heart closing the SL valvesAortic pressure raises when the aortic valve closesThis is caused by the blackflowing blood rebounding off the closed valve cusps an event beginning at the dicrotic notchOnce again the ventricles are totally closed chambers4281 Pressure changes in the heartoWhen blood pressure on the atrial side of the AV valves exceeds that in the ventricles the AV valves open and ventricular filling occursAtrial pressure drops to its lowest point and ventricular pressure risesoThe same process occurs on the right as the left the only difference is the pressureThe systole and diastole are typical 2410 mmHg rather then 12080 mmHg Both sides eject the same amount of blood4283 Sounds of the HeartoThe pause indicates the period when the heart is relaxingoThelub or first sound occurs as the AV valves are closingSignifies the point when ventricular pressure rises above atrial pressureTends to be longer louder and more resonant then the second soundoThe dub or second sound occurs as the SL valves snap shutResults in a short snap sound4284 Heart Murmurs
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