The Heart

ATRIAL SYSTOLE Prior to atrial systole, blood has been flowing passively from the atrium into the ventricle through the open AV valve. During atrial systole the atrium contracts and tops off the volume in the ventricle with only a small amount of blood. Atrial contraction is complete before the ventricle begins to contract The end of diastole

ISOVOLUMETRIC CONTRACTION The atrioventricular (AV) valves close at the beginning of this phase. Electrically, ventricular systole is defined as the interval between the QRS complex and the end of the T wave (the Q-T interval). Mechanically, ventricular systole is defined as the interval between the closing of the AV valves and the opening of the semilunar valves (aortic and pulmonary valves). ISOVOLUMETRIC CONTRACTION The beginning of systole

Systole The time period when the heart is contracting. The period specifically during which the left ventricle of the heart contracts. The systolic pressure is specifically the maximum arterial pressure during contraction of the left ventricle of the heart. In a blood pressure reading, the systolic pressure is typically the first number recorded. For example, with a blood pressure of 120/80 ("120 over 80"), the systolic pressure is 120. By "120" is meant 120 mm Hg (millimeters of mercury).

RAPID EJECTION The semilunar (aortic and pulmonary) valves open at the beginning of this phase.

REDUCED EJECTION The end of systole At the end of this phase the semilunar (aortic and pulmonary) valves close.

ISOVOLUMETRIC RELAXATION The beginning of diastole At the beginning of this phase the AV valves are closed.

RAPID VENTRICULAR FILLING Once the AV valves open, blood that has accumulated in the atria flows rapidly into the ventricles.

REDUCED VENTRICULAR FILLING (DIASTASIS)

Diastole The time period when the heart is in a state of relaxation and dilatation (expansion). The diastolic pressure is specifically the minimum arterial pressure during relaxation and dilatation of the ventricles of the heart. Diastole is the time when the ventricles fill with blood. In a blood pressure reading, the diastolic pressure is typically the second number recorded. For example, with a blood pressure of 120/80 ("120 over 80"), the diastolic pressure is 80. By "80" is meant 80 mm Hg (millimeters of mercury).

Bicuspid valve: One of the four valves of the heart, this valve is situated between the left atrium and the left ventricle. It permits blood to flow one way only, from the left atrium into the left ventricle This valve is more commonly called the mitral valve because it has two flaps (cusps) and looks like a bishop's miter or headdress. Tricuspid valve: One of the four heart valves, the tricuspid valve is the first one that blood encounters as it enters the heart. The tricuspid valve stands between the right atrium and right ventricle and allows blood to flow only from the atrium into the ventricle. Descending aorta: The descending aorta is the part of the aorta, the largest artery in the body, that runs down through the chest and the abdomen. The descending aorta starts after the arch of the aorta and ends by splitting into two great arteries (the common iliac arteries) that go to the legs.

What Happens to your Heart

cardiac output = heart rate x stroke volume Cardiac output, - is the total volume of blood pumped by the ventricle per minute, or simply the product of heart rate (HR) and stroke volume (SV). The stroke volume at rest in the standing position averages between 60 and 80 ml of blood in most adults. Thus at a resting heart rate of 80 beats per minute the resting cardiac output will vary between 4.8 and 6.4 L per min. cardiac output = heart rate x stroke volume (CO = HR x SV) The average adult body contains about 5 L of blood, so this means all of our blood is pumped through our hearts about once every minute.

Only 15% of the resting cardiac output goes to muscle. Couch Potatoes Only 15% of the resting cardiac output goes to muscle.

Resting Cardiac Output Cardiac output = Heart rate x Stroke Cardiac output = 72 x 70 Cardiac output = 5040 ml/min Cardiac output = 5.04 L/min 70 beats/minute X 60 minutes/hour = 4,200 beats/hour 4,200 beats/hour X 24 hours/day = 100,800 beats/day 100,800 beats/day X 365 days/year = 36,792,000 beats/year

Active Life Style During vigorous exercise, the muscles receive 60% to70% of the cardiac output.

Exercising Cardiac Output The cardiac output of a conditioned athlete increases 8 times above resting cardiac output to approximately 40 liters for one minute of maximal work with an accompanied stroke volume of 210 ml per beat.

Exercising Cardiac Output During the initial stages of exercise, increased cardiac output is due to an increase in both heart rate and stroke volume. When the level of exercise exceeds 40% to 60% of the individual's capacity, stroke volume has either plateaued or begun to increase at a much slower rate. Thus further increases in cardiac output are largely the result of increases in heart rate.