L-20 regulation Of COP And VR

Question 1

What is cardiac output

Answer 1

Volume of blood ejected from ventricles each minute

Question 2

Formula of COP

Answer 2

SV x HR

Question 3

What is the stroke volume

Answer 3

Volume of blood ejected from the ventricles each beat

Question 4

How much blood does the ventricle receive during diastole

Answer 4

130-140 ml

End diastolic volume

Question 5

How much blood is ejected each systole

Answer 5

60-70 ml

Stroke volume

Question 6

How much blood remains in the ventricle

Answer 6

60-70 ml

End systolic volume

Question 7

Cardiac output(figure)

Answer 7

4.9-5.2 liters/min

Question 8

What is the ejection fraction and its figure and how is it calculated

Answer 8

Assesses efficiency of heart
Stroke volume/end diastolic volume
60-70%

Question 9

How can we inc cardiac output

Answer 9

Inc stroke vol
Inc heart rate
Or both

Question 10

What are the factors determining the stroke volume

Answer 10

Preload: vol at end of diastole
Afterload: resistance left ventricle must overcome from aorta
Contractility

Question 11

How can the preload affect venous return

Answer 11

Position
Skeletal muscle pump
Valves in veins
Abdominal thoracic pump
Venomotor tone
Residual pressure
Ventricular suction

Question 12

How can position affect venous return

Answer 12

In supine position The pressure gradient between the veins in the right atrium tends to return the blood back to the heart with no effect of gravity and this disappears in standing position

Question 13

How can the skeletal muscle pump affect the venous return

Answer 13

Skeleton muscles contract and squeeze on the vein making the blood flow upwards increasing the Venous return

Question 14

How can the valves in veins and vascular sheath affect venous return

Answer 14

As of the artery pulsates blood in adjacent vein is displaced upward to the heart which increases the COP and heart beats more powerfully then this massaging action is increased and so the VR increases

Question 15

How can the abdominal thoracic pump affect venous return

Answer 15

During inhalation the thoracic cavity decreases and presses on the abdominal cavity which causes the vena cava to return more blood

Question 16

How can the venomotor tone affect Venous return

Answer 16

Sympathetic alpha 1 adrenoreceptors receptors
Can cause Veno constriction or Veno dilation
Sympathetic tone decreases with old age

Question 17

How can residual pressure affect venous return

Answer 17

Whenever there is a difference in pressure between two location fluid flows from the region of high-pressure to that of low pressure
Pressure in arteries is greater than veins so pressure gradient drives the blood from arteries to veins and increases venous return

Question 18

Define residual pressure

Answer 18

Pressure from left side of the heart which is ultimately responsible for pushing of blood behind towards the right side of the heart
(Vis a tergo)

Question 19

How can ventricular suction affect venous return

Answer 19

▪️Pressure in right atrium is normally about zero mmHg
▪️During ventricular contraction the atrial ventricular ring is pulled down as a result of this the atria expands
▪️This creates a negative pressure in the right atrium and the negative pressure is also created during sudden rush of blood from Atria to ventricle
▪️this negative pressure exerts suction effect on the great veins and draws blood into the atrium(vis a fronte)