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CVS > L04: Regulation Of Cardiac Output > Flashcards

L04: Regulation Of Cardiac Output Flashcards

1
Q

What does the cardiac output measure

A

Volume of blood pumped per minute

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2
Q

What is the cardiac output equation

A

Heart rate x stroke volume

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3
Q

What is the equation for stroke volume

A

End diastolic volume- end systolic volume

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4
Q

What is the end diastolic volume

A

The volume in the ventricles at the end of diastole

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5
Q

What is the end systolic volume

A

The volume of blood left behind in the ventricles at the end of systole/contraction

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6
Q

Therefore what is another equation of the cardiac output

A

Heart rate x (EDV-ESV)

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7
Q

Therefore what are the 3 ways cardiac output can be maintained

A

Heart Rate
EDV
ESV

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8
Q

How can we change stroke volume by changing EDV and ESV

A

Increase EDV

Decrease ESV

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9
Q

What is stroke volume

A

The amount of blood ejected into the aorta/pulmonary from the ventricles

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10
Q

How do muscles contract

A

1) calcium enters cardiac muscles by L-typed calcium channels
2) calcium then stimulates sarcodoplasmic reticulum to release more calcium by the calcium release channels
3) calcium released binds to troponin c to move the regulatory complex on the actin binding site
4) myosin head binds to actin binding site to form cross bridges
5) relaxation occurs by renovating calcium back into the sarcoplasmic reticulum by SERCA
6) SERCA is regulated by phospholambon

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11
Q

How do we increase the force of contraction

A

Increase the number of cross bridges formed by increases intracellular calcium or calcium sensitivity

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12
Q

What is the starlings law relationship between

A

End diastolic volume

Stroke volume

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13
Q

What does the starlings law show

A

And increase in EDV increases stroke volume

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14
Q

Why does the stroke volume increase when end diastolic volume increase in the starlings law

A

1) More blood fills the heart due to a higher EDV
2) More stretch occurs in the ventricles
3) More force of contraction due to sarcomere length increases and actin myosin cross bridged increasing as a result of it
4) Bigger contraction gives higher stroke volume

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15
Q

In starlings law when the EDV increases what determines this increase of EDV

A

Venous return

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16
Q

If the venous return is from the right side of the heart does this mean only the right ventricle EDV is affected

A

No because the stroke volume pumped from the right side will enter the left side of the heart to increase its left side EDV.

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17
Q

What does the starlings law ensure in terms of both sides of the heart

A

Their stroke volumes are the same

18
Q

What are the factors that affect venous return to the right side

A 
Blood volume 
Skeletal muscle pump
Respiratory pump
Venous tone 
Gravity
19
Q

How does blood volume increase venous return

A

Increase in blood volume increases venous return

20
Q

Where is the skeletal muscle found

A

In the leg

21
Q

How does the skeletal muscle pump increase venous return

A

Blood is propelled through the valances by the skeletal muscle pump to the heart

22
Q

How does the respiratory pump increase venous return

A

When we breath in diaphragm flattens and chest-wall expands
Abdominal pressure increase and thorax pressure decreases
Pressure gradient suck blood from abdominal vena cava to thoracic vena cava
More blood is delivered to the heart

23
Q

How does venous tone increase venous return

A

Contraction of the veins called venoconstriction means more blood is return to the heart

24
Q

Which nervous system is involved in venoconstriction

A

Sympathetic NS

25
Q

How does gravity effect venous return

A

In a standing position gravity causes blood to accumulate to lower body and less blood is return to the heart
To fix this problem if the patient lies down the blood will become evenly distributed so venous return will not decrease

26
Q

How does the heart rate affect EDV

A

Increase in heart rate decreases EDV and this will decrease stroke volume

27
Q

What is increased contractility about

A

An increase in sympathetic activity which increases calcium and therefore the number of bridges formed

28
Q

What does an increase in contractility do to the ESV

A

Decrease it

29
Q

What does an increased contractility do to the SV

A

Increase it

30
Q

Describe what happens during increased contractility

A

1) Sympathetic nerves that innervate the ventricular muscle release noradrenaline which act on beta 1 adrenoceptor to increase calcium channel opening
2) This leads increase n calcium influx
3) Increase in calcium increase cross bridges formed
4) Contraction therefore increases

31
Q

What is the difference between starlings law and increased contractility

A

In starlings law the sacromeres stretch due to more EDV. There is the same calcium conc
In increased contractility sympathetic nervous activity increases to increase calcium concentration.

32
Q

What is a similarity of the starling law and increased contractility

A

They both result in more cross bridges formed

33
Q

What is afterload

A

The force that hear must contract again to eject stroke volume

34
Q

In after-load what must the ventricular pressure be again aortic pressure to eject blood into the aorta

A

Higher than the aortic pressure

35
Q

What increase the aortic pressure

A

Total peripheral resistance

36
Q

If there is an increase in TPR what will happen to the aortic pressure

A

Increase

37
Q

What will an increase in TPR mean in terms of stroke volume

A

Stroke volume will decrease as after load increases.

38
Q

What is the heart determined by

A

Sympathetic and parasympathetic activity

39
Q

What is the EDV determined by

A 
Intrinsic factors such as :
Venous return (Pre-load)
40
Q

What is the ESV determined by

A

Contractility

CVS (19 decks)

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