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Physiology > L20 - Cardiovascular System 3 > Flashcards

L20 - Cardiovascular System 3 Flashcards

1
Q

Why are valves integral to healthy heart function?

A

ensure unidirectional flow

open / close passively

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2
Q

What causes the opening and closing of valves in the heart?

A

pressure differences between components of the heart

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3
Q

When do the atrioventricular valves close?

A

when the ventricles start to contract

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4
Q

When do the semilunar valves close?

A

when the ventricles relax

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5
Q

When do valves close in general?

A

when pressure in current compartment becomes greater than pressure in previous compartment

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6
Q

What are the sounds of the heart? What causes these sounds?

A

sound 1 and sound 2

occur when heart valves close (sudden turbulent flow and vibration)

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7
Q

What is sound 1 caused by?

A

closure of atrioventricular (AV) valves (contraction)

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8
Q

What is sound 2 caused by?

A

closure of semilunar valves (relaxation)

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9
Q

What will cause the AV valves to close? (contraction or relaxation of ventricles / greater pressure in ventricles than atria or greater pressure in atria than ventricles)

A

pressure in ventricles become greater than pressure in atria

ventricles start contracting

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10
Q

What affects the movement of blood?

A 
heart - source of energy
gravity
skeletal muscle
diaphragm movements
elastic tissue
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11
Q

What is systolic BP?

A

max pressure exerted in arteries when blood is ejected into them during systole (heart contracting phase)

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12
Q

What is diastolic BP?

A

min pressure within arteries when blood draining off into remainder of vessels during diastole (heart relaxing / filling phase)

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13
Q

What is pulse pressure?

A

a measure of strength of pressure wave

difference between systolic and diastolic BP

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14
Q

What is mean arterial pressure?

A

average pressure responsible for driving blood forward into tissues throughout cardiac cycle

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15
Q

Why is regulation of MAP important?

A

essential for efficient function and life
low BP = dizziness, organ failure
high BP = stroke, aneurysm

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16
Q

What determines MAP?

A

how much blood is pumped out per unit time

how difficult / easy is it for the blood to move through the system

17
Q

What determines how much blood is pumped out per unit time?

A

stroke volume x heart rate = cardiac output

18
Q

What determines how difficult / easy it is for the blood to move through the system?

A

total peripheral resistance (TPR) = resistance of the peripheral circulation

19
Q

What is MAP proportional to?

A

cardiac output x total peripheral resistance

20
Q

How is stroke volume calculated? How can stroke volume be increased?

A

end diastolic volume minus end systolic volume
increasing end diastolic volume or decreasing systolic volume via more forceful contractions resulting in less blood leftover in the heart

21
Q

What is cardiac output?

A

volume of blood pumped by one ventricle in a given period of time

22
Q

What is stroke volume?

A

amount of blood pumped by one ventricle during a contraction

23
Q

What is stroke volume? What affects stroke volume?

A

force of ventricular contraction
affected by:
length of muscle fiber (volume of blood in chamber at start of contraction)
contractility of heart (neural influences)

24
Q

What is the stretch-force relationship in heart? (Frank-Starling Law)

A

as more blood enters the heart, length of muscle fibres stretches towards optimum length resulting in increased contractile force

25
Q

What is end-diastolic volume determined by?

A

venous return which is controlled by the skeletal muscle pump, the respiratory pump and neural control of the venous system

26
Q

What does neural control of the venous system involve?

A

sympathetic tone and varying degree of vasoconstriction

27
Q

How does norepinephrine affect stroke volume?

A

increases stroke volume as it increases the strength of contraction of muscle fibres

28
Q

How does the sympathetic nervous system modulate heart rate?

A

changes ion permeability
depolarises
reaches threshold sooner
β1-receptors (noradrenaline)

29
Q

How does the parasympathetic nervous system modulate heart rate?

A 
changes ion permeability
hyperpolarizes
takes longer to reach threshold
muscarinic receptors (ACh)
30
Q

How does the sympathetic nervous system affect conduction of AV node?

A

enhances conduction

31
Q

How does the parasympathetic nervous system affect conduction of AV node?

A

slows conduction

32
Q

How does the body maintain the same mean arterial pressure if TPR is changing all the time?

A

modulating cardiac output because MAP = CO x TPR

33
Q

Why is there a fall in cardiac output when we stand?

A

pooling of blood in legs -> reduced venous return -> reduced CO -> fall in MAP

34
Q

Can the body measure cardiac output?

A

not directly

for a given TPR, MAP is an indication of the adequacy of cardiac output

Physiology (33 decks)

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