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B7- MASS TRANSPORT > 7.5- THE CARDIAC CYCLE > Flashcards

7.5- THE CARDIAC CYCLE Flashcards

1
Q

How many times does the human heart undergo a sequence of events each minute when at rest?

A

sequence of events that’s repeated around 70 times each minutes when at rest

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2
Q

What is the sequence of events that the heart undergoes called?

A

cardiac cycle

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3
Q

What are the two phases to the beating of the heart?

A

contraction (systole)

relaxation (diastole)

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4
Q

How does contraction occur separately?

A

occurs separately in ventricles + atria

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5
Q

As contractions occurs separately in ventricles + atria, how many stages is it described in?

A

in two stages

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6
Q

For some of the time, how does relaxation take place?

A

relaxation takes place simultaneously in all chambers of heart

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7
Q

Through where does blood return to the atria of the heart? (2) (diastole)

A 
through pulmonary vein (from lungs)
vena cava (from body)
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8
Q

What rises as the atria fill? (diastole)

A

as atria fill, pressure in them rises

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9
Q

What happens when the pressure in the atria exceeds that in the ventricles? (diastole)

A

atrioventricular valves open allowing blood to pass into ventricles

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10
Q

What is the passage of blood from atria to ventricles aided by? (diastole)

A

aided by gravity

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11
Q

When blood passes from the atria to ventricles, how are the muscular walls of the atria + ventricles? (diastole)

A

muscular walls of atria + ventricles relaxed at this stage

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12
Q

What does the relaxation of the ventricle walls cause? (diastole)

A

causes them to recoil + reduces pressure within the ventricles

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13
Q

When the ventricle walls relax + reduces pressure within the ventricles, what is the pressure in the ventricles like in comparison to that in the aorta + pulmonary artery? (diastole)

A

pressure lower than in the aorta + pulmonary artery

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14
Q

As the pressure in the aorta + pulmonary artery is higher when the muscular walls of ventricles relax, what happens? (diastole)

A

semi-lunar valves in aorta + pulmonary artery closes, accompanied by characteristic ‘dub’ sound of heart beat

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15
Q

What forces the remaining blood into the ventricles from the atria, after diastole? (atria systole)

A

contraction of atrial walls, along with recoil of relaxed ventricle walls

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16
Q

How are the muscle of the ventricle walls throughout this stage? (atria systole)

A

throughout this stage muscle of ventricle walls remains relaxed

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17
Q

Why is there a short delay after atrial systole? (ventricular systole)

A

to allow ventricles to fill with blood

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18
Q

What happens after the short delay to allow ventricles to fill with blood? (ventricular systole)

A

ventricle walls contract simultaneously

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19
Q

What happens when the ventricle walls contract simultaneously? (ventricular systole)

A

increases blood pressure within them, forcing them to shut atrioventricular valves + preventing backflow of blood into atria

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20
Q

What is the ‘lub’ characteristic of the heart beat? (ventricular systole)

A

valves closing

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21
Q

What happens with the atrioventricular valves closed? (ventricular systole)

A

pressure in ventricles rises further

22
Q

What happens once the pressure in the ventricles exceed that in the aorta + pulmonary artery? (ventricular systole)

A

blood forced from ventricles into vessels

23
Q

What sort of walls do the ventricles have? (ventricular systole)

A

thick muscular walls

24
Q

What does it mean as the ventricles have thick muscular walls? (ventricular systole)

A

means they can contract forcefully

25
Q

As the ventricles have thick muscular walls that can contract forcefully, what does this mean? (ventricular systole)

A

creates high pressure necessary to pump blood around body

26
Q

Where does the thick wall of the left ventricles have to pump blood? (ventricular systole)

A

has to pump blood to extremities of body

27
Q

Where does the relatively thinner wall of the right ventricle have to pump blood to? (ventricular systole)

A

has to pump blood to lungs

28
Q

How is blood kept flowing in one direction through the heart + around the body?

A

by pressure created by heart muscle

29
Q

From what region will blood to?

A

blood will always move from region of higher pressure to one of lower pressure

30
Q

What is used in circumstances where pressure differences would result in blood flowing in opposite direction from that which is desirable?

A

valves used to prevent any unwanted backflow of blood

31
Q

What are valves in the cardiovascular system designed to do?

A

open whenever difference in blood pressure either side of them favours movement of blood in required direction

32
Q

When are valves in the cardiovascular system designed to close?

A

when pressure differences reversed, that is, when blood would tend to flow in opposite direction to that which is desirable

33
Q

Examples of valves in the cardiovascular system? (3)

A

atrioventricular valves
semi-lunar valves
pocket valves

34
Q

Where are the atrioventricular valves?

A

between left atrium + ventricle and right atrium + ventricle

35
Q

What do the atrioventricular valves do?

A

prevent backflow of blood when contraction of ventricles means ventricular pressure exceeds atrial pressure

36
Q

What does the closer of the atrioventricular valves ensure?

A

ensures that when ventricles contract, blood within them moves to aorta + pulmonary artery rather than back to atria

37
Q

Where are the semi-lunar valves?

A

in aorta + pulmonary artery

38
Q

What do the semi-lunar valves do?

A

prevent backflow of blood into ventricles when pressure in aorta + pulmonary artery exceed that in ventricles

39
Q

When does the pressure in aorta + pulmonary artery exceed that in the ventricles? (semi-lunar valves)

A

when elastic walls of aorta + pulmonary artery recoil, increasing pressure within them

and when ventricle walls relax reducing pressure within ventricles

40
Q

Where are the pocket valves?

A

in veins that occur throughout the venous system

41
Q

What do the pocket valves ensure?

A

ensure that when veins squeezed, e.g. when skeletal muscles contract, blood flows back towards heart rather than away from it

42
Q

What are the valves made up of?

A

number of flaps of tough, but flexible, fibrous tissue, which are cusp-shaped

43
Q

What happens when the pressure is greater on the convex side of the cusps rather than the concave side? (valves)

A

they move apart to let blood pass between cusps

44
Q

What happens when pressure on concave side than on convex side? (valves)

A

blood collects within ‘bowl’ of cusps

this pushes them together to form tight fit that prevents passage of blood

45
Q

What sort of circulatory system do mammals have?

A

closed circulatory system

46
Q

What does it mean to have a closed circulatory system?

A

blood confined to vessels

47
Q

What does blood being confined to vessels in a closed system allow?

A

pressure within them to be maintained + regulated

48
Q

What is cardiac output?

A

volume of blood pumped by one ventricle of heart in one minute

49
Q

What unit is cardiac output usually measured in?

A

dm3min-1

50
Q

What two factors does cardiac output depend on?

A 
heart rate (rate at which heart beats)
stroke volume (volume of blood pumped out at each beat)
51
Q

What is the equation for cardiac output?

A

heart rate * stroke volume

B7- MASS TRANSPORT (9 decks)

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