Define cardiac output
The quantity of blood ejected out from each
ventricle per minute is called cardiac output.
What is the other name of cardiac output
called minute volume under normal condition
What is the equation of cardiac output
C.O = Stroke Volume X Heart Rate
= 70 ml X 72 /min = 5.5 L/min
Define venous return
It is the quantity of blood flowing from the veins into the
right atrium each minute.
What is the formula of venous return
Venous Return = Arterial B.P / Total Peripheral Resistance
Normal V.R =……
= C.O (Frank starling law) within limits
Define Stroke Volume
Amount of blood pumped out by each ventricle
during systole (each beat) - 70 ml
What is the formula of stroke volume
Stroke volume =EDV-ESV
Define:
End diastolic volume:
End systolic volume :
End diastolic volume: It is the amount of blood remaining in each
ventricle at the end of diastole
End systolic volume : Amount of blood remained in the ventricles
after the systole
What is the amount volume of each
End diastolic volume: 110 to 120 ml.
End systolic volume :40 -50 ml
T or F
Cardiac output varies widely with the level of activity of the body.
True
what is the factors, directly affect cardiac output:
1. The basic level of body metabolism
2. whether the person is exercising
3. The person’s age
4. The size of the body
Dose surface area has an effect on cardiac index
Experiments have shown that the cardiac output increases approx.
in proportion to the surface area of the body.
Define cardiac index
cardiac output per square meter of body surface
area.
What is the formula of cardiac index
C.O. at rest per square meter of body surface area.
C.I. = 5.5 / 1.7
= 3 L/min/m2
At what age cardiac index is. Maximum and why
C.I. is max at age of 10 yrs then it decreases
Cuss surface area is more
Preload and afterload
Define preload
Preload : It is the stretching of the cardiac muscle fibers at
the end of diastole just before contraction.
It is the end diastolic volume that stretches the right or
left ventricle of the heart to its greatest geometric
dimensions under variable physiologic demand.
What preload indicate
It indicates ventricular filling before its contraction.
Define Afterload
Afterload: It is the force against which the ventricles must
contract and eject the blood.
It is the tension or stress developed in the wall of the left
ventricle during ejection.
How can afterload force determine
by The arterial pressure.
Define minute volume and its formula
Minute Volume: It is the amount of blood pumped out by
each ventricle in one minute.
▪ M.V = Stroke Volume X Heart Rate
▪ M.V = 5L /ventricle / minute
Define cardiac reserve
Cardiac Reserve: It is the maximum amount of blood that
can be pumped out by the heart above normal value.
What is the most significant effect of cardiac reserve in cardiac output
It can increase C.O during stress like exercise.
In which of the following cardiac reserve is maximum
In which of the following cardiac has minimum cardiac reserve
What is the main function of the heart
pump blood to meet the metabolic needs of the body
What is the 2 mechanism to regulat heart pump
Intrinsic regulation
Extrinsic regulation
Define
▪ Extrinsic regulation
Intrinsic regulation (Pump behavior without external influence)
Extrinsic regulation (Pump response to external influences)
To what Intrinsic regulation depend on
Ventricular contractile strength Ventricular filling(Frank Starling law )
What kind of respond that Extrinsic regulation respond
Nervous regulation
response to circulating catecholamines -
contractility
▪ Aortic/Pulmonary arterial pressure
What happen when there is Increases in diastolic stretch (preload)
increases strength of contraction
Increase stroke volume (up to a limit)
T or f
Right atrial stretch may also increase heart rate By Mechanical stimulation of AV node
F
Right atrial stretch may also increase heart rate
▪ Mechanical stimulation of SA node - 10% to 15% increase in HR
Define Frank-Starling Mechanism
It states that within limits, higher the initial length of the
cardiac muscle fibers, more forceful will be their
contraction.
What Diastolic stretch, during filling, determines??
stroke volume
What is the relationship between Strength of contraction and Ventricular Filling
Strength of contraction directly proportional to Ventricular Filling
What Determines Ventricular Filling?
1. Energy gradient (pressure and kinetic) between atria &
ventricles during diastole
2. Ease of ventricular filling (myocardial compliance)
3. Time available for filling (Diastolic duration)
Which of the following has higher pressure and higher kinetic energy during diastole
What permits filling during diastole
Relaxing/relaxed myocardium
What limit filling during diastole
Pericardium, and ventricular connective tissue
What is Extrinsic Influences on Pump Function
▪ Neural regulation of myocardium
▪ Regulation by circulating agents
▪ Influence of after-load (Aortic/Pulmonary artery pressure)
What kind of neural regulation that atria and ventricle receive
▪ Atria receive sympathetic and parasympathetic innervation
▪ Ventricles receive sympathetic innervation
How can circulating agents effect Extrinsic regulation
Myocardial cells have many different types of receptors on their
sarcolemma That regulat heart pump in extrinsic regulation
Explain Autonomic regulation of Cardiac Output
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