APHY 164 - Cardiac Output

Cardiac Output (CO)

The amount of blood pumped by a single ventricle in one minute. HR x SV = CO

Stroke Volume (SV)

The amount of blood ejected from a ventricle in one heartbeat (contraction).

Heart Rate (HR)

number of heart beats per minute

Cardiac Output (CO) equation

CO = heart rate (HR) x stroke volume (SV), healthy individual 5L/min

End Diastolic Volume (EDV)

volume of blood in each ventricle at end of ventricular diastole (relaxation/filling)

End Systolic Volume (ESV)

volume of blood remaining in each ventricle after systole (contraction)

Preload

degree of stretch of the cardiac muscle fibers at the end of diastole (relaxation/filling)

Afterload

the amount of resistance to ejection of blood from the ventricle

Venous Return

the amount of blood returned to the heart, determines preload

Positive ionotropic agents

Increase the strength of heart muscle contractions, increase the levels of calcium -> increases number of cross bridges -> increases the force of contraction

Negative ionotropic agents

decrease the strength of heart muscle contractions, decrease the levels of calcium -> decreases number of cross bridges -> decreases the force of contraction

Positive chronotropic agents

factors that increase the heart rate

Negative chronotropic agents

factors that decrease the heart rate

Contractility of the heart

The strength of contraction of the heart muscle at any given end-diastolic volume

Cardioacceleratory center

sends signals through sympathetic nerves to increase both heart rate and force of contraction, stimulates SA and AV nodes, heart muscle, and coronary arteries

Cardioinhibitory center

sends signals through parasympathetic vagus nerve to decrease heart rate, inhibits SA and AV nodes