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CVS (Semester 2) > Control Of Cardiac Output > Flashcards

Control Of Cardiac Output Flashcards

1
Q

What are the two factors which determine arterial pressure?

A

Cardiac output and total peripheral resistance

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2
Q

What determines venous pressure?

A

This is a balance between the rate at which blood enters the venous system and the rate at which it is pumped out of the heart.

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3
Q

What can be said about changes to arterial and venous pressure and how the other responds?

A

When arterial pressure increases, venous pressure decreases and vice versa.

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4
Q

What is the relationship between TPR and the body’s need for blood?

A

Inversely proportional, as the body’s need for blood increases, there needs to be vasodilation and so a decrease in TPR.

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5
Q

How do changes in metabolism cause changes at the heart?

A

Changes in metabolism cause changes in TPR which affects both arterial and venous pressure. These generates signals which lead to changes at the heart.

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6
Q

How can we calculate stroke volume?

A

End diastolic volume - end systolic volume.

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7
Q

What effect does higher venous pressure have in the ventricles?

A

Higher venous pressure leads to increased ventricular filling as there is an increased pressure gradient.

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8
Q

What is starlings law of the heart about stretching cardiac tissue?

A

The more the heart muscle is stretched, the more it pumps.

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9
Q

What is the relationship between venous pressure and Stroke volume?

A

Increased venous pressure leads to increased stroke volume.

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10
Q

What are alterations in contractility called?

A

This is called positive and negative inotropy.

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11
Q

What two factors determine force of contraction?

A

End diastolic volume and contractility

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12
Q

On a graph of stroke volume against end diastolic volume, what is the effect of altered contractility?

A

This leads to shifting of the curve left to right.

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13
Q

What is aortic impedance?

A

This is where there is high aortic pressure and so this makes it harder to eject blood.

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14
Q

What is preload?

A

This is the volume of blood in the ventricles at the end of diastole

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15
Q

Name some factors which can lead to increased preload.

A

Hypervolemia, regurgitation of cardiac valves, heart failure

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16
Q

What is afterload?

A

The resistance the LV must overcome to circulate blood

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17
Q

Under what circumstances will afterload be increased?

A

Hypertension and increased total peripheral resistance.

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18
Q

What detects arterial blood pressure?

A

Baroreceptors. These cause autonomic control over the heart.

19
Q

When blood pressure decreases, how does the autonomic nervous system correct this?

A

There is an increase in sympathetic drive which increases heart rate and contractility, and a decrease in parasympathetic action on pulse.

20
Q

What detects increase in venous pressure?

A

The bainbridge reflex, which results in a parasympathetic drive and an increase in heart rate.

21
Q

Name the organs which always require a stable perfusion.

A

Heart, brain and kidneys.

22
Q

How does blood flow change with intense exercise?

A

There is increased blood flow to the skeletal muscle and skin and decreased blood flow to the gut.

23
Q

Why does cardiac fitness effect cardiac output?

A

If someone is more cardiac fit, then they will have a greater ventricular distensibility and contractility.

24
Q

Where in the body are baroreceptors found?

A

Carotid sinus and aortic arch.

25
Q

What blood vessels are responsible for TPR?

A

Arterioles

26
Q

What vessels can control RA filling and therefore stroke volume?

A

The veins/ great veins which are reservoirs for blood with large volumes and low pressures.

27
Q

What is the functional reserve in the CVS?

A

There are many capillary beds which are not perfused and so these serve as a functional reserve.

28
Q

At what mean arterial blood pressure does perfusion become inadequate?

A

65mmHg.

29
Q

What happens immediately in the CVS when a person stands up?

A

There is a drop in central venous pressure which leads to reduced atrial filling and therefore a drop in mean arterial blood pressure.

30
Q

Hat is the orthostatic response to standing up?

A

Heart rate will increase and so will TPR to increase mean arterial blood pressure.

31
Q

What is the importance of smooth muscle tone of the veins on standing up?

A

This means that there is less pooling of blood to the legs which increases CVP because more blood is pumped back to the heart.

32
Q

When the body has a delayed CVS response to standing up, what happens?

A

When there is a delayed CVS response, this leads to dizziness and fainting which can result in syncope. This is due to inadequate cerebral blood flow.

33
Q

What is the systemic effect of eating a large meal?

A

This causes an increase in action of the parasympathetic nervous system.

34
Q

What is the effect on eating a large meal on TPR?

A

There is decreased TPR because there are more local dilators and autacoids and also an increased activity of the parasympathetic nervous system.

35
Q

What two changes occur to the CVS as a result of eating a large meal?

A

There is an increase in cardiac output due to increased RA filling and there is also a decrease in arterial pressure.

36
Q

What response do baroreceptors initiate to eating a large meal?

A

They detect the fall in MABP and so increase cardiac output which reduces CVP and increases arterial pressure.

37
Q

What changes occur to the heart during strenuous exercise?

A

There is increased cardiac output due to an increase in pulse and Stroke volume.

38
Q

What happens the instance exercise begins?

A

Vasodilation leads to an increased central venous pressure. This causes a fall in blood pressure.

39
Q

In exercise, what is the benefit of muscle contraction?

A

Muscle contraction for the exercise also aids circulation.

40
Q

What happens during haemorrhage?

A

This is stopped by clotting, and when there is blood loss this leads to hypovolaemia shock. Blood loss causes decreased CVP, Sv, CO and MABP.

41
Q

What occurs in the tissue during haemorrhage which makes the situation worse?

A

Locally, there is metabolite build up and so this causes vasodilation which lowers TPR and causes a further drop in MABP

42
Q

What is the major influence of baroreceptors in haemorrhage?

A

They increase sympathetic activity on the heart, particularly to increase pulse rate.

43
Q

What can occur to major organs as a result of haemorrhage?

A

They can experience reduced perfusion which can lead to delayed death due to inability to maintain MABP.

44
Q

Where in the brain does control of cardiac output occur?

A

In the medulla. Information from baroreceptors is sent here and then this coordinates the autonomic nervous system response.

CVS (Semester 2) (17 decks)

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