Physiology: Cardiac Output Flashcards
Stroke volume
The amount of blood the heart pumps through each cycle
Is directly proportional to
- contractility
- preload
Is indirectly proportional to
- afterload
Frank-starling mechanism
Length tension curve of the heart
States that as preload/ venous return/ (EDV) is increased as the cardiac output and stroke volume increase.
EDV is directly related to cardiac output and stroke volume
Afterload
Arterial pressure ejection (amount of pressure that heart needs to pass in order to eject the blood).
- this is blood pressure
The pressure in the arteries determines how much blood is ejected.
- increased TPR/SPR = increased afterload
Afterload is indirectly proportional to stroke volume
- decreased afterload = increased stroke volume
Preload
The venous filling pressure or end diastolic volume (EDV)
- venous dialation = increased preload
- venous constriction = decreased preload
The amount of blood filling into the right atrium and right ventricle determines the amount of stroke volume and cardiac output.
Directly proportional to cardiac output and stroke volume
Contractility of cardiac cells are controlled by what factors
Autonomic nerve function
Circulating agents (hormones, drugs, etc.)
DP/dt max value
The value that determines the amount of contractility a heart is producing to work.
The steeper the slope = greater value = more pressure
Contractility is directly proportional to cardiac output/ stroke volume
- The greater the Dp/dt max (contractility), the greater the cardiac output
Inotropic
Medical term for contractility
Positive inotropic effects = more calcium in cardiac myocytes = more cardiac output.
Negative inotropic effects = less calcium in cardiac myocytes = less cardiac output.
What is the relationship between ejection fraction and contractility?
Directly proportional
Stroke work equals what?
Pressure (pressure = pressure peak @ systole peak) x volume (volume = EDV-ESV)
