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Human Physiology 2 > Week Three > Flashcards

Week Three Flashcards

1
Q

Define Heart Rate

A

the number of cardiac cycles or ‘beats’ per minute (units: BPM)

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2
Q

Define stroke volume

A

the volume of blood pumped out of the left ventricle in one heart beat (unit: mL)

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3
Q

Define cardiac output

A

the volume of blood pumped out of the left ventricle in 1 minute (units: L/min)

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4
Q

Define venous return

A

the volume of blood coming back into the heart in 1 minute (VR = CO)

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5
Q

Define End-diastolic volume

A

the amount of blood in the ventricle at the end of diastole

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6
Q

Define End-systolic volume

A

the amount of blood in the ventricle at the end of systole

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7
Q

How do you calculate stroke volume?

A

End diastolic volume - end systolic volume

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8
Q

How do you calculate Cardiac output

A

Heart rate x stroke volume

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9
Q

Name the three factors that affect stroke volume

A

preload, contractility, and after load

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10
Q

What is preload? How does it affect stroke volume?

A
  • the amount of stretch of the sarcomeres in ventricular myocytes before the contract. This is mainly determined by End-diastolic Volume
  • the relationship between stretch and force: higher volume of blood in ventricles → greater stretch of the myocardium → greater force of contraction
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11
Q

What are the two factors that influence End-diastolic volume?

A
  • length of time the ventricle spends in diastole
  • amount of blood returning to the heart from the systemic circuit (venous return)
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12
Q

What is contractility?

A

the heart’s intrinsic ability to contract (generate force to pump)

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13
Q

What is a inotropic agent?

A

agents that affect contractility

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14
Q

What is after load?

A

the force the ventricles must overcome in order to eject blood into their arteries (e.g. higher pressure in the aorta = higher force needed to eject blood out of the left ventricle)

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15
Q

What factors affect the venous return?

A

exercise and blood volume

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16
Q

What factors affect the contractility? i.e inotropic agents?

A

sympathetic nervous system (epinephrine and norepinephrine)

17
Q

What factors influence after load?

A

mean atrial pressure (blood pressure)

18
Q

How does a higher preload affect stroke volume?

A

higher preload = higher EDV → stretches ventricle cardiac muscle cells → more potential for actin myosin overlap → greater force of contraction → more blood ejected → lower ESV → higher stroke volume

19
Q

How does higher contractility affect stroke volume?

A

higher contractility → greater force of contraction → more blood ejected → lower ESV → higher stroke volume

20
Q

How does a lower afterload affect stroke volume?

A

lower afterload → ventricles pumping against lower resistance → lower ESV → higher stroke volume

21
Q

How does low preload affect stroke volume?

A

low preload → cardiac muscle cells are much less stretched → lower EDV → lower stroke volume

22
Q

How does low contractility affect stroke volume?

A

low contractility → heart contracts more weakly → higher ESV → lower stroke volume

23
Q

How does a high after load affect stroke volume?

A

high afterload → ventricle is pumping against a higher resistance

24
Q

What are factors that influence heart rate known as?

A

chronotropic agents

25
Q

What is a positive chronotropic agent

A

anything that increases rate at which SA node fires
- includes the sympathetic nervous system, certain hormones, and elevated body temperature

26
Q

What is a negative chronotropic agent?

A

anything that decreases rate at which the SA node fires is a negative chronotropic agent
- includes the parasympathetic nervous system and decreased body temperature

27
Q

How does the sympathetic nervous system affect cardiac output?

A

norepinephrine and epinephrine increase heart rate and increase the contractility of the myocytes

28
Q

What does a positive inotropic effect mean?

A

increased contractility

29
Q

How does the parasympathetic nervous system affect cardiac output?

A

acetylcholine mainly targets the SA node and causes a decrease in heart rate

30
Q

What is systolic pressure?

A

the pressure of the blood against the artery walls during ventricular systole (around 120 mmHg at rest)

31
Q

What is diastolic pressure?

A

the pressure of the blood against the artery walls during ventricular diastole (around 80 mmHg at rest)

32
Q

What does the systemic atrial blood pressure reflect?

A

the driving pressure of blood flow through the arteries

33
Q

How do we calculate mean atrial pressure?

A

MAP = diastolic pressure + 1/3(systolic pressure - diastolic pressure)

34
Q

How do you calculate pulse pressure?

A

systolic BP - Diastolic BP

Human Physiology 2 (9 decks)

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