reg of cardiac ouptut Flashcards
whats the cardiac output equation?
stroke volume x hear rate
whats the equation for stroke volume
end diastolic volume - end systolic volume
what is systole?
period of contraction –> blood eject to the lung or the body
whats the diastole?
period of relaxation –> heart fills with blood
what is end diastolic volume ( EDV )
the volume in the ventricles at the end of the relaxation period usually 110-120 ml
what is end systolic volume ( ESV)
the volume in the ventricles at the end of the contraction period, البقايا
usually 40-50
so in normal scenarios sv is 120-50 = 70 and co for example is
70 x 72 bpm for example is = 50000 ml/min or 5 L/min
whats cardiac index? and its equation?
Cardiac index = CO
—————-
body surface area
what are the factors that regulate stroke volume thus also regulate co?
1- Contractility
2- Preload
3- Afterload
how is contractility related to sv? and how its regulated?
Increased contractility will decrease ESV which will increase SV and vice versa
- Contractility is regulated by autonomic nervous system
how is preload related to sv?
increased preload will increase EDV will increase SV and vice versa
-regulated by frank starling mechanisim ( intrinsic factors )
how is afterload related to sv?
increased afterload will increase ESV which will DECREASE SV and vice versa
- regulated by arterial blood pressure and resistance
how is heart rate controlled?
ANS - para and sympathetic nerves
whats the definition of contractility and what are the factors affecting it? and example
its the strength of contraction
influenced by neurotransmitters and hormones which AFFECT THE INTRACELLUAR CALCIUM = more calcium = stronger contraction
increased sympathetic stimulation to the heart will increase contractility
what are the markers/indices of contractility
1- Change of pressure vs change in time DELTA P/DELTA T
increased pressure will cause increased contractility
2- ejection fraction
whats the equation of ejection fraction?
ejection fraction = Stroke volume
——————————————–
End diastolic volume
what would happen if contractility is increased?
1- increased delta p/ dt which increases slope and rate of pressure development
2- increased peak left ventricle pressure
3- increased rate of relaxation due to the increased calcium sequestration حبس
4- Decreased systolic intervals ( time between contraction )
whats the relation between contractility and ca concentration?
they are related directly
more intracellular ca = increased contractility
Positive inotropic effect
Caclcium will induce calcium release from reticulum and it binding to troponin = contraction
what are the ANS sympathetic nerve effect on contraction and how it works?
sympathetic nervous system will cause release NOREPINEPHRINE which will bind to B1 receptors and increase CAMP and then will it increase calcium and release calcium from SR –> contraction
POSITIVE INOTROPIC EFFECT
what are the ANS parasympathetic effect on contraction and how it works?
parasympathetic will cause acetylcholine release which will bind to muiscarnic receptor and WILL DECREASE CAMP and it will decrease calcium and decrease contractility –> NEGATIVE INOTROPIC
whats relation between cardiac glycosides on contractility?
cardiac glycosides are positive inotropic agents , they increase contractility
how do cardiac glycosides work? and give one example of them
- Inhibit Na/K atpase pump which will move 3 sodium out and 2 potassium in to return stuff back to normal after depolarization ,
The cardiac glycoside will inhibit this and will cause NA accumulation inside the cell and this Sodium will cause calcium retention inside the cell by inhibiting the exchange transporter which moves ca out and brings in 3 sodium this mechanism is usually used to get rid of calcium and putting sodium in,
when theres a lot of sodium inside the exchange transporter wont work cuz theres a lot of sodium inside and cant bring more in, so calcium will stay inside and it will cause calcium retention inside the cell —> CA IN = INCREASED CONTRACTILITY
the sodium retention may also cause arrhytmias and irregular beats and rate
Digoxin is an example and it works like this
whats the relation between heart rate and contractility?
when theres increased heart rate theres increased contractility cuz both of them are depending on calcium , increased ca = increased hr = increased contractility
what is preload?
stretch of ventricle wall tension at the end of diastole js prior to contraction ITS THE SAME EDV
what are indices/markers for preload? and give example of scenarios
1- Left ventricle EDV
2- Left ventricle End diastolic pressure -> pretty much the same as EDV
3-Left atrial pressure –> cuz whatever in the atrium will go to the ventricle
4- Pulmonary venous pressure –> whatever comes from the lung will go to the atrium then to the ventricle
5- plumonary wedge pressure ( Swan ganz catheter )
Hemorrhage –> decreased preload cuz low volume
Excess IV fluid infusion –> increase preload
Venous dilation –> decreased preload
Venous constriction –> increased preload
