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Physiology & Pharmacology of Systems > Introduction to the Cardiovascular System > Flashcards

Introduction to the Cardiovascular System Flashcards

1
Q

What is normal pressure in the vena cava?

A

3-8mmHg

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2
Q

How do you convert kPa to mmHg?

A

Multiply by 7.5

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3
Q

At what velocity is blood entering the right atrium?

A

25cm/sec

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4
Q

What is the name of the process by which the end of passive ventricular filling is topped up with extra blood from the atria immediately prior to ventricular contraction?

A

Arterial kick

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5
Q

What is the relationship between heart rate and the % of ventricular filling that the atrial kick is responsible for?

A

As HR INCREASES the % of ventricular filling that the atrial kick is responsible for also INCREASES as the time for passive ventricular filling has decreased.

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6
Q

What is a normal VENOUS p02?

A

40mmHg

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7
Q

What is a normal VENOUS pC02?

A

46mmHg

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8
Q

What is a normal VENOUS 02 content?

A

150ml/L

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9
Q

What is a normal VENOUS C02 content?

A

520ml/L

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10
Q

Describe the currents which lead to SA node depolarisation and repolarisation.

A

Depolarisation = Ca+ current influx (ICa)

Repolarisation = K+ current efflux (IK)

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11
Q

Describe the currents which lead to depolarisation and repolarisation in all areas of the heart apart from the SA node. Include the maintained depolarisation phase (plateau) and the name of the channel responsible for this.

A

Depolarisation = Na+ current influx (INa)

Maintained depolarisation = Ca2+ current influx (ICa) via voltage gated “L-type” calcium channels

Repolarisation = K+ current efflux (IK)

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12
Q

What is another name for the “L-type” calcium channels?

A

DHP or dihydropyridine channels (named after “L-type” calcium channel blocker drugs which contain a pyridine group)

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13
Q

Explain “L-type” calcium channels.

A

These are voltage induced channels which allow an influx of Ca2+ into the cell and trigger calcium induced calcium release from the sarcoplasmic reticulum via activation of the ryanodine receptor (RyR)

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14
Q

Explain the atrial systole phase of the cardiac contraction cycle.

Which valves are involved and where are they located?

What is the volume of the ventricles after this phase? What name is given to this measurement.

A

Passive filling of the atria and ventricles via open tricuspid (right) and mitral (left) valves is boosted by atrial kick as the atria contract. This allows the ventricles to fill to around 120ml by the end of their diastolic phase, this value therefore being makes the end-diastolic volume.

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15
Q

Name the 7 phases of the cardiac cycle.

A 
Atrial systole
Isovolumetric ventricular systole
Rapid ventricular ejection
Reduced ventricular contraction
Isovolumetric ventricular relaxation
Rapid ventricular filling 
Reduced ventricular filling
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16
Q

Explain the isovolumetric ventricular systole phase of the cardiac contraction cycle.

A

There is ventricular contraction but no change in its volume. The pressure will increase and the tricuspid and mitral valves will shut to prevent “back-flux”.

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17
Q

Explain the rapid ventricular ejection phase of the cardiac contraction cycle.

A

The ventricular pressure overcomes the pulmonary arterial/aortic pressure and the ventricles eject blood rapidly.

18
Q

Explain the reduced ventricular contraction phase of the cardiac contraction cycle.

What were the maximum pressures reached in both the left and right ventricles?

What volume of blood do the ventricles eject? What is the normal ejection fraction?

A

Ejection slows as the force of contraction slows.

LV = reaches max pressure of 120mmHg
RV = reaches max pressure of 20mmHg

Pressure in the pulmonary artery and aorta rise above that of the ventricles and ejection stops.

End-diastolic volume = 50ml (120 - 50 = 70ml ejected) therefore ejection fraction is roughly 60%

19
Q

How would you work out the cardiac output from a HR of 70bpm and an ejection fraction of 60% (70ml).

A

Cardiac output = volume of blood ejected from the heart per minute.

70 x 70 = 4900ml = 5L/min

20
Q

Explain the isovolumetric relaxation phase of the cardiac contraction cycle.

A

The ventricles are relaxing and the pressure is decreasing. There is no volume change.

21
Q

Explain the rapid ventricular filling phase of the cardiac contraction cycle.

A

The ventricular pressures fall below that of the atria and rapid filling occurs of the ventricles.

22
Q

Explain the reduced ventricular filling phase of the cardiac contraction cycle.

A

The ventricle filling slows as they fill.

23
Q

What is preload?

A

It is the left ventricular end diastolic volume.

24
Q

What does an increase in preload result in? What is this relationship called?

A

An increase in ventricular stretch and therefore an increase in contraction strength (inotropy) and therefore stroke volume and subsequently cardiac output and blood pressure overall due to the length-tension relationship in cardiomyocyte sarcomeres. This is due to the frank-starting law of the heart.

25
Q

What is afterload.

A

The load against which the ventricles have to overcome in order to eject blood. It is related to the pulmonary artery and aortic pressures.

26
Q

What does an increase in afterload result in?

A

Increased afterload will decrease stroke volume and therefore decrease cardiac output and blood pressure overall.

27
Q

What will an increase in afterload do to the frank-starling curve?

A

Shift it to the right and down. For the same LVEDP will result in a lower stroke volume.

28
Q

What does chronotropy relate to?

A

Heart rate

29
Q

What does inotropy relate to?

A

Contractility

30
Q

What does lusitropy relate to?

A

The rate of myocardial relaxation. It is related to the speed at which calcium can be removed back into the sarcoplasmic reticulum via sarcoplasmic reticulum calcium ATPase (SERCA) ion channel pump.

31
Q

Why is does pulmonary arterial pressure still drive blood through its system even though it is very low (8-20mmHg)?

What law relates the resistance of a tube to the length and radius?

A

It’s has low pulmonary vascular resistance due to short, wide vessels.

This is shown by (part of) poiseuille’s law:

Resistance ∝ length/radius^4

32
Q

What is a normal ARTERIAL p02?

A

100mmHg

33
Q

What is a normal ARTERIAL pC02?

A

40mmHg

34
Q

What is a normal ARTERIAL 02 content?

A

200ml/L

35
Q

What is a normal ARTERIAL C02 content?

A

480ml/L

36
Q

What % of the blood is in the venous system at any one point?

A

70%

37
Q

What is pulse pressure?

A

Systolic - diastolic pressure

38
Q

What is another name for the dicrotic notch on an arterial trace and what does it represent?

A

Incisura

The closure of the aortic valve

39
Q

What is the calculation for MAP?

A

MAP = diastolic + (1/3 pulse pressure)

40
Q

Where is 75% of the blood ejected during ventricular systole stored immediately after?

A

In the aorta

41
Q

What is the equation that links pressure, flow and resistance?

A

Δ pressure = flow (C.O) x resistance (T.P.R)

42
Q

What are the skeletal muscle pump and the respiratory pump?

A

These help drive blood back to the heart through the venous system.

The skeletal muscle pump works via skeletal muscle contraction and the respiratory by decreasing the thoracic pressure during inspiration.

Physiology & Pharmacology of Systems (21 decks)

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