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Cardiology > Cardiac Physiology > Flashcards

Cardiac Physiology Flashcards

1
Q

What is the end systolic volume (ESV)?

A

The ESV is the volume of blood in the heart after systole or a contraction - this is also the point where diastole or relaxation of the heart muscle is about to begin.

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2
Q

What is the end diastolic volume (EDV)?

A

The EDV is the volume of blood in the heart and the end of diastole or the “filling” stage of the cardiac cycle - this is also the point where systole (or contraction) is about to begin.

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3
Q

What is the stroke volume?

A

Stroke volume is the difference between EDV and ESV

or amount of blood pushed out of the heart per heart beat SV= EDV - ESV

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4
Q

What is the ejection fraction?

A 
Ejection fraction (EF) is the stroke volume divided by the EDV. It is the proportion of blood (when at maximum blood filling) that is ejected into systemic circulation. 
EF = SV/EDV
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5
Q

What is (under normal circumstances) a normal EF?

A

55-60% - the heart does not normally eject all of the blood in the heart.

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6
Q

What is cardiac output?

A

Cardiac output is the volume of blood that the heart is ejecting per unit of time.
CO = HR x SV

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7
Q

What is venous return?

A

Venous return is the amount of blood returned to the heart via the venous system.

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8
Q

Since the circulatory system is a closed system, which value should the venous return be equal to?

A

The cardiac output - the amount of blood returned to the heart should be equal to amount of blood leaving the heart.

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9
Q

What is the total peripheral resistance (TPR)?

A

The total peripheral resistance is the resistance to blood flow from peripheral structures (like the organs and arteries of the body).

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10
Q

Would vasoconstriction lead to an increase or decrease in TPR?

A

An increase in total peripheral resistance since the diameter has decreased when the vessel is vasoconstriction.

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11
Q

Would vasodilation lead to a decrease or increase in TPR?

A

A decrease in TPR since the diameter of the vessels has increased.

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12
Q

During exercise the body aims to maximise blood flow to which areas?

A

The heart and skeletal muscles.

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13
Q

What is the trigger for blood divergence to the heart and skeletal muscle during exercise?

A

Muscle hypoxia - lack of oxygen to skeletal muscle tissue.
As the muscles are contracted ATP is used - this leads to decreased oxygen which results in localised hypoxia of muscle tissue.

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14
Q

What arm of the autonomic NS mediates the body’s response to exercise?

A

Sympathetic NS

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15
Q

Name some mediators released into the blood stream causing vasodilatation as a result of exercise.

A

Adenosine
Lactate
Carbon dioxide
Potassium

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16
Q

A key physiologic response during exercise is vasodilation. TPR is decreased when there is vasodilation - what would be the benefit of decreasing TPR?

A

Decreased TPR activates the SNS which allows key changes to take place during exercise (e.g. increased HR, contractility).

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17
Q

A drop in TPR (associated with exercise) leads to activation of what?

A

The SNS

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18
Q

List the SNS changes associated with exercise.

A

Increased contractility - increases SV
Increased HR - increases CO
Divergence of flow- decreased to GIT and increased flow to skeletal muscle.

19
Q

During exercise will the systolic blood pressure rise or fall?

A

The SBP will rise - this is because the cardiac output is increasing (resulting in more blood in the vessels) and more pressure (more work done by the heart).

20
Q

During exercise does the diastolic blood pressure stay normal, rise or fall

A

The DBP will usually decrease slightly or stay normal - this is because of a drop in TPR (localised blood vessels near skeletal muscle will vasodiliate (resulting in a fall in resistance from peripheral structures).

21
Q

Why does the partial pressure increase during exercise?

A

The partial pressure rises during exercise because there is a widening of the difference between SBP and DBP - recall the equation for PP= SBP - DBP

22
Q

Fill in the blanks.
During exercise there is a __________ (decrease/increase) in diastole duration leading to ________ (increased/decreased) coronary filling time.

A

decrease; decrease
During exercise the HR increases so there is less ventricular filling time - this leads to less blood in the coronary arteries.

23
Q

In order to combat the decrease in diastole during exercise, the coronary arteries must ___________ to ensure adequate perfusion of heart tissue.

A

vasodilate

24
Q 
During exercise the heart has increased oxygen demand - what will the heart do in order to increase oxygen supply to the myocardium?
A) arterial vasodilation
B) increase PaO2
C) vasodilation of coronary vessels 
D) increase haemoglobin
A

C) vasodilation of coronary vessels

The heart tissue is already at maximum oxygen extracting capacity - vasodilation will increase amount of blood.
Wrong answers -
A - will not affect myocardial blood supply and is a PNS response.
B - the body is not physically able to increase PaO2!
D- the body cannot change haemoglobin content in the blood

25
Q

Does preload increase or decrease during exercise?

A

The preload increases

26
Q

The increase in venous contraction due to sympathetic innervation causes a rise in _______ and _______.

A

preload and EDV - this also leads to a rise in cardiac output.

27
Q

Does the ejection fraction increase or decrease during exercise?

A

The EF increases - due to more vigorous contractions

28
Q

The end systolic volume decreases during exercise. Why is this?

A

The contractility of the heart increases during exercise - less blood is left within the left ventricle and being pumped into the systemic circulation.

29
Q

The EDV only changes minority during exercise. Why is this?

A

The HR rises during exercise - there is less ventricular filling time and as such less blood is able to be filled when the heart is relaxed.

30
Q

Using your knowledge of the changes to EDV and ESV during exercise, why does the EF increase.

A

The ESV decreases and EDV decreases (minorly) so following the EF equation - EF= EDV-ESV/EDV the major decrease in ESV will cause the EF to rise.

31
Q

What does Lusitropy mean?

A

Lusitropy describes myocardial relation (it is essentially the opposite of contractility). - how vigorously the walls of the left ventricle come apart during diastole

32
Q

During exercise lusitropy does what?

A

It increases - which results in an increase in preload and CO.

33
Q

Lusitropy is the rate of myocardial relaxation. What is the name of the key regulatory protein during lusitropy?

A

Phospholamban

34
Q

Which enzyme does phospholamban inhibit?

A

SERCA - sarcoplasmic reticulin calcium - ATPase

35
Q

What is the function of the enzyme SERCA in cardiac myocytes?

A

SERCA regulates calcium uptake from the cytosol of cardiac myocytes into the sarcoplasmic reticulum.

36
Q

SERCA is a pump that transports calcium ions from the cytoplasm into the sarcoplasmic reticulum. Its action can be inhibited by phospholamban. How can the inhibitory effects of phospholamban on SERCA be reversed?

A

Beta adrenergic stimulation will cause phosphorylation of phospholamban - reversing its inhibitory effects on SERCA

37
Q

What is the effect of SERCA?

A

SERCA is an ion channel which allows re-uptake of calcium ions into the sarcoplasmic reticulum.

In the heart, this causes a DECREASE in contractility as calcium ions are stored within the SR.

38
Q

Describe the concept of auto regulation of organs with changing blood pressure.

A

Autoregulation describes the changes in blood pressure and flow occurring in the body and how organs combat these changes using local metabolites to determine the degree of vasoconstriction.

39
Q

What local metabolites does the heart use in auto-regulation?

A

carbon dioxide
adenosine
nitric oxide

40
Q

What local metabolites does the brain use in auto-regulation?

A

carbon dioxide

pH of blood

41
Q

What local metabolites does the kidneys use in auto-regulation?

A

blood pressure

NaCl (delivered to the macula densa cells)

42
Q

How do the lungs control blood pressure through the mechanism of vasoconstriction?

A

Hypoxia is a trigger for the lungs to vasoconstrict.

43
Q

What local metabolites does skeletal muscle use in auto-regulation?

A

Lactate
Adenosine
Potassium

Cardiology (8 decks)

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