Unit 1 - CV System The Heart PART G Flashcards
Cardiac Output
Volume of blood ejected by each ventricle over time (i.e. rate at which each ventricle pumps blood)
What is cardiac output determined by?
Determined by the rate at which the ventricles contract (HEART RATE) and the volume of blood pumped per contraction (STROKE VOLUME).
If average heart rate at rest is 72 beats/min and average stroke volume at rest is 70 mL/beat, then average cardiac output is:
5040 mL/min or ~5.0 L/min
During exercise, cardiac output can increase up to ____
5x
Cardiovascular athletic training/exercise can further increase cardiac output (up to ______
40 L/min).
What does Cardiovascular athletic training/exercise do?
Training increases heart muscle mass (which increases stroke volume), and decreases resting heart rate (maximal heart rate stays the same). Overall training increases the difference between resting and exercise values of both heart rate and stroke volume, resulting in higher cardiac output during exercise
What is cardiac output a measure of?
cardiac performance
How do you measure cardiac output?
Heart rate x Stroke volume = cardiac output
Cardiac output is the SAME for BOTH ventricles. BUT, if 1 side of the heart begins to fail (unable to pump efficiently), CO becomes mismatched. So…
blood pools in the circulation behind the WEAKER side of the heart
Stroke Volume =
EDV - ESV
End Diastolic Volume (EDV) =
amount of blood in each ventricle at the end of the ventricular relaxation period and, just prior to the start of ventricular contraction. On average, at rest = 135mL.
AKA volume of blood BEFORE contraction
What is End Diastolic Volume (EDV) on average, at rest?
On average, at rest = 135mL.
End Systolic Volume (ESV) =
amount of blood left in each ventricle just after ventricular ejection. On average, at rest = 65 mL.
AKA volume of blood AFTER contraction
What is End Systolic Volume (ESV) on average, at rest?
On average, at rest = 65 mL.
Therefore average resting stroke volume =
135 mL – 65 mL = 70 mL
During the cardiac cycle, the EDV is the _______ ventricular volume, and ESV the _______ ventricular volume.
MAXIMUM
MINIMUM
The precise values of these maxima and minima can vary depending on conditions (e.g. during exercise…
EDV stays the SAME or INCREASES; and ESV DECREASES, allowing for at least the maintenance or an increase in stroke volume at higher heart rates).
Both stroke volume and heart rate are variable and can be modified by both the nervous and endocrine systems and other mechanisms. As a result,…
the body can adjust cardiac output by changing either the heart rate or stroke volume (or both) to respond to the body’s needs
Ejection fraction
the volume of blood ejected from the ventricle in 1 contraction = ejection fraction (% of EDV ejected with 1 contraction (STROKE VOLUME/EDV)
Ex:
EDV = 70 mL
SV = 135 ml
therefore, 70/135 = 52% –> ventricle is ejecting 52% of the blood that was in it @ the end of relaxation & filling
