Cardiac Output

Question 1

cardiac output at rest

Answer 1

the amount of blood pumped by the heart in a 1 minute period
L/min = heart rate (beats/minute) x stroke volume (L/beat)

Question 2

cardiac output during exercise

Answer 2

cardiac output increases rapidly at the onset of exercise and then plateaus when steady-state is achieved

Question 3

cardiac output increases due to

Answer 3

increased heart rate
increased stroke volume
enhanced cardiac filling in diastole (increased end-diastolic volume)
frank-starling law of the heart
greater systolic emptying
sympathetic nervous system release of catecholamines increases myocardial contractile force to increase stroke power and therefore systolic emptying

Question 4

frank-starling law of the heart

Answer 4

the force of contraction is directly proportional to the initial length of the muscle fiber

Question 5

cardiac output distribution

Answer 5

an increase in cardiac output with exercise produces a proportionate increase in the capacity to circulate oxygen
redistribution of blood flow to skeletal muscle during exercise is controlled by hormonal vascular regulation and local metabolic conditions in response to environmental stress, levels of fatigue, and intensity/mode/duration of exercise
increased coronary blood flow supplies the increased myocardial oxygen need with exercise
cerebral blood flow increases during exercise by 25-30% compared with resting flow

Question 6

endurance training and cardiac output

Answer 6

training decreases heart rate at rest and a given submaximal intensity
rest: increase in parasympathetic and decrease in sympathetic activity
training increases stroke volume at rest, submaximal intensity, and at maximal exertion
increase in volume of blood in the ventricles at the end of heart muscle relaxation
increase in plasma volume with training
increase in diastolic filling time due to decrease in heart rate (at rest and submax)
increase in ventricular compliance (reduced cardiac stiffness)
decrease in blood pressure of the aorta
increase in contractility of the heart
increase in sympathetic activity
increase in left ventricular mass of the heart

Question 7

heart rate and training

Answer 7

resting and submaximal heart rate is decreased with exercise training
rest: primarily due to increased parasympathetic activity
submaximal exercise: primarily due to a small decrease in sympathetic discharge

Question 8

cardiac hypertrophy

Answer 8

long-term aerobic training increases the heart’s mass and volume
increased size of the left-ventricular cavity
modest thickening of the left-ventricular wall
the athlete’s heart does not represent a dysfunctional organ, but rather normal systolic and diastolic functions and superior functional capacity for stroke volume and heart rate

Question 9

cardiac output and training

Answer 9

trained persons perform submaximal exercise at the same or a lower cardiac output than untrained
an increase in maximum cardiac output represents the most significant adaption in cardiovascular function with aerobic training

Question 10

oxygen consumption and cardiac output

Answer 10

oxygen consumption increases during exercise by increased total quantity of blood pumped by the heart
there is a close relationship between maximum cardiac output and maximal oxygen consumption (VO2 max)
stroke volume is a major determinant of differences in VO2 max in trained and untrained
not the only factor

Question 11

maximal oxygen consumption

Answer 11

a high VO2 max requires the integrated and high-level response of diverse physiological systems