CVS - responses of the whole system Flashcards

1
Q

What is the cardiac ouput like during heavy exercise?

A

~ 25L/min

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2
Q

Which organs get a decrease in the percentage of the cardiac output during heavy exercise?

A

GIT, kidneys, bone and brain.

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3
Q

Which organs receive the same percentage of the cardiac output during heavy exercise?

A

Heart

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4
Q

Which organs get a increase in the percentage of the cardiac output during heavy exercise?

A

Skin and skeletal muscle.

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5
Q

What is a typical cardiac output range?

A

5-15l/min (>20l/min if very unfit)

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6
Q

What is a typical heart rate range?

A

60-180bpm (upper limit 220-age)

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7
Q

What is the typical stroke volume range?

A

~60-150ml (>200 if very fit)

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8
Q

How is the heart rate regulated?

A
  1. Self-generated: SAN/AV node

2. Modulated - by ANS/ hormonal control

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9
Q

How is stroke volume regulated?

A
  1. Venous return: CVP-RAP drives ventricular filling
  2. Aortic pressure (drives baroreceptor sensor output)
  3. ANS/ hormonal control
  4. Cardiac fitness: ventricular distensibility/ conctractility
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10
Q

Where are baroreceptors found? What is the difference in the pressures they detect?

A
  1. Aortic arch - sensitive to higher pressures (>100 mmHg increase firing)
  2. Carotid body - sensitive to lower pressures (>50 mmHg increase firing).
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11
Q

What is the role of baroreceptors?

A

They send signals to the cardiovascular centre in the medulla when they are stretched by pressure. This results in sympathetic activity changes which modulates cardiac output (SV and HR).

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12
Q

What modulates the vasomotor tone of arterioles and pre-capillary sphincters and therefore TPR?

A

SNS, metabolites and autocoid control.

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13
Q

What is the role of veins/ great veins in controlling stroke volume?

A

They act as reservoir for blood. Their large volume and low pressure regulate RA filling and therefore stroke volume.

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14
Q

What is the normal range in central venous pressure?

A

+2-10 mmHg

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15
Q

Why is it serious if mean arterial blood pressure falls below 60mmHg?

A

Tissue perfusion becomes inadequate and if it continues for any length of time, there is a serious risk of organ failure.

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16
Q

Define hyperemia:

A

An excess of blood in the vessels supplying an organ or other part of the body.