2. Systole: Period of ejection. Continued ventricular Semilunar valves closed Semilunar valves opened AV valves closed AV valves closed 1. Systole: Period of isovolumic contraction. Ventricular contraction causes the AV valves to close, which is the beginning of ventricular systole. The semilunar valves were closed in the previous diastole and remain closed during this period. 2. Systole: Period of ejection. Continued ventricular contraction pushes blood out of the ventricles, causing the semilunar valves to open. Semilunar valves closed Semilunar valves closed AV valves opened AV valves closed 5. Diastole: Active ventricular filling. The atria contract and complete ventricular filling. 3. Diastole: Period of isovolumic relaxation. Blood flowing back toward the relaxed ventricles causes the semilunar valves to close, which is the beginning of ventricular diastole. Note that the AV valves closed, also. Semilunar valves closed 4. Diastole: Passive ventricular filling. The AV valves open and blood flows into the relaxed ventricles, accounting for most of the ventricular filling. AV valves opened

Semilunar valves closed AV valves closed Systole: Period of isovolumic contraction. Ventricular contraction causes the AV valves to close, which is the beginning of ventricular systole. The semilunar valves were closed in the previous diastole and remain closed during this period.

Systole: Period of isovolumic contraction. Semilunar valves opened Semilunar valves closed AV valves closed AV valves closed Systole: Period of isovolumic contraction. Systole: Period of ejection.

Semilunar valves opened AV valves closed Systole: Period of ejection. Continued ventricular contraction pushes blood out of the ventricles, causing the semilunar valves to open.

Systole: Period of ejection. Semilunar valves opened AV valves closed Systole: Period of ejection. Semilunar valves closed AV valves closed Diastole: Period of isovolumic relaxation.

Semilunar valves closed AV valves closed Diastole: Period of isovolumic relaxation. Blood flowing back toward the relaxed ventricles causes the semilunar valves to close, which is the beginning of ventricular diastole. Note that the AV valves closed, also.

Diastole: Period of isovolumic relaxation. Semilunar valves closed AV valves closed Semilunar valves closed Diastole: Period of isovolumic relaxation. AV valves opened Diastole: Passive ventricular filling.

Semilunar valves closed AV valves opened Diastole: Passive ventricular filling. The AV valves open and blood flows into the relaxed ventricles, accounting for most of the ventricular filling.

Diastole: Active ventricular filling. Semilunar valves closed AV valves opened Diastole: Active ventricular filling. Semilunar valves closed AV valves opened Diastole: Passive ventricular filling.

Semilunar valves closed AV valves opened Diastole: Active ventricular filling. The atria contract and complete ventricular filling.

Systole: Period of isovolumic contraction. Semilunar valves closed AV valves closed Systole: Period of isovolumic contraction. Semilunar valves closed AV valves opened Diastole: Active ventricular filling.

Lub-dub, lub-dub 4 valves in the heart Heart sounds Heart murmur flaps of connective tissue prevent backflow Heart sounds closing of valves “Lub” force blood against closed AV valves “Dub” force of blood against semilunar valves Heart murmur leaking valve causes hissing sound blood squirts backward through valve SL AV AV

Electrical signals heart pumping controlled by electrical impulses stimulates ventricles to contract from bottom to top, driving blood into arteries allows atria to empty completely before ventricles contract heart pumping controlled by electrical impulses signal also transmitted to skin = EKG

Cardiac Cycle How is this reflected in blood pressure measurements? ventricles fill How is this reflected in blood pressure measurements? systolic ________ diastolic The cardiac cycle. For an adult human at rest with a pulse of about 75 beats per minute, one complete cardiac cycle takes about 0.8 second. During a relaxation phase (atria and ventricles in diastole), blood returning from the large veins flows into the atria and ventricles. A brief period of atrial systole then forces all remaining blood out of the atria into the ventricles. During the remainder of the cycle, ventricular systole pumps blood into the large arteries. Note that 7/8 of the time—all but 0.1 second of the cardiac cycle—the atria are relaxed and are filling with blood returning via the veins. chambers fill pump (peak pressure) _________________ fill (minimum pressure) 110 ________ 80 ventricles pump

Measurement of blood pressure if systolic > 150 or if diastolic > 90 hypertension = (high blood pressure)

Electrocardiogram (ECG) P = atrial depolarization ~ 0.1 sec atria contracts QRS = ventricular depolarization ventricles contract (lub), contraction stimulated by Ca++ uptake T = ventricular repolarization  ventricles relax (dub)