B – The Cardiovascular System The structure and function of arteries, capillaries and veins The structure and function of the heart Pathology of cardio vascular disease (CVD) Blood glucose levels and obesity

KA 6: The structure and function of the heart 2.6 Key Topics REVISION: Structure of the heart (D) Blood Pressure (A) Cardiac function and cardiac output (B) Cardiac cycle (C) The structure and function of cardiac conducting system

KA 6a: Learning Outcomes Define the terms ‘cardiac output’, ‘heart rate’ and ‘stroke volume’ State the formula for cardiac output Carry out cardiac output calculations

Key Terms Heart Rate (pulse) (HR) Number of heartbeats that occurs per minute. Stroke Volume (SV) Volume of blood expelled by each ventricle on contraction. (The stronger the contraction, the greater the stroke volume). Cardiac Output (CO) The volume of blood pumped through each ventricle per minute. (creates the pulse) CO = HR x SV SV is calculated using measurements of ventricle volumes from an echocardiogram and subtracting the volume of the blood in the ventricle at the end of a beat (called end-systolic volume) from the volume of blood just prior to the beat (called end-diastolic volume). The term stroke volume can apply to each of the two ventricles of the heart, although it usually refers to the left ventricle. The stroke volumes for each ventricle are generally equal, both being approximately 70 ml in a healthy 70-kg man The left and right ventricles pump the same volume of blood through the aorta and pulmonary artery.

Calculations CO = HR x SV A: 5.8/60 = 0.09 B: 6.1/68 = 0.08 C: 7.2/72 = 0.1 D: 7.6/78 = 0.09 ANSWER: C HR x SV 80 x 120 =

Calculations CO = HR x SV The graph below shows how pulse rate and stroke volume change with the rate of oxygen uptake What is the cardiac output when the oxygen uptake is 0.6 L/min ? What is the cardiac output when the oxygen uptake is 1.6 L/min? 2006 old HB

Calculations CO = HR x SV The graph below shows how pulse rate and stroke volume change with the rate of oxygen uptake What is the cardiac output when the oxygen uptake is 0.6 L/min ? When oxygen uptake = 0.6… HR = 80 and SV = 120 BUT we need to change 120 cm3 into L (/1000) CO = HR x SV CO = 80 x 0.12 CO = 9.6 L/min HR x SV 80 x 120 =

Calculations CO = HR x SV The graph below shows how pulse rate and stroke volume change with the rate of oxygen uptake What is the cardiac output when the oxygen uptake is 1.6 L/min ? When oxygen uptake = 1.6… HR = 110 and SV = 150 BUT we need to change 150 cm3 into L (/1000) CO = HR x SV CO = 110 x 0.15 CO = 16.5 L/min HR x SV 80 x 120 =

KA 6a: Learning Outcomes Define the terms ‘cardiac output’, ‘heart rate’ and ‘stroke volume’ State the formula for cardiac output Carry out cardiac output calculations