7.5- THE CARDIAC CYCLE

Question 1

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

Answer 1

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

Question 2

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

Answer 2

cardiac cycle

Question 3

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

Answer 3

contraction (systole)

relaxation (diastole)

Question 4

How does contraction occur separately?

Answer 4

occurs separately in ventricles + atria

Question 5

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

Answer 5

in two stages

Question 6

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

Answer 6

relaxation takes place simultaneously in all chambers of heart

Question 7

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

Answer 7

through pulmonary vein (from lungs)
vena cava (from body)

Question 8

What rises as the atria fill? (diastole)

Answer 8

as atria fill, pressure in them rises

Question 9

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

Answer 9

atrioventricular valves open allowing blood to pass into ventricles

Question 10

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

Answer 10

aided by gravity

Question 11

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

Answer 11

muscular walls of atria + ventricles relaxed at this stage

Question 12

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

Answer 12

causes them to recoil + reduces pressure within the ventricles

Question 13

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)

Answer 13

pressure lower than in the aorta + pulmonary artery

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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

Question 16

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

Answer 16

throughout this stage muscle of ventricle walls remains relaxed

Question 17

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

Answer 17

to allow ventricles to fill with blood

Question 18

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

Answer 18

ventricle walls contract simultaneously

Question 19

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

Answer 19

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

Question 20

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

Answer 20

valves closing

Question 21

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

Answer 21

pressure in ventricles rises further

Question 22

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

Answer 22

blood forced from ventricles into vessels

Question 23

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

Answer 23

thick muscular walls

Question 24

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

Answer 24

means they can contract forcefully

Question 25

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

Answer 25

creates high pressure necessary to pump blood around body

Question 26

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

Answer 26

has to pump blood to extremities of body

Question 27

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

Answer 27

has to pump blood to lungs

Question 28

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

Answer 28

by pressure created by heart muscle

Question 29

From what region will blood to?

Answer 29

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

Question 30

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

Answer 30

valves used to prevent any unwanted backflow of blood

Question 31

What are valves in the cardiovascular system designed to do?

Answer 31

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

Question 32

When are valves in the cardiovascular system designed to close?

Answer 32

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

Question 33

Examples of valves in the cardiovascular system? (3)

Answer 33

atrioventricular valves semi-lunar valves pocket valves

Question 34

Where are the atrioventricular valves?

Answer 34

between left atrium + ventricle and right atrium + ventricle

Question 35

What do the atrioventricular valves do?

Answer 35

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

Question 36

What does the closer of the atrioventricular valves ensure?

Answer 36

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

Question 37

Where are the semi-lunar valves?

Answer 37

in aorta + pulmonary artery

Question 38

What do the semi-lunar valves do?

Answer 38

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

Question 39

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

Answer 39

when elastic walls of aorta + pulmonary artery recoil, increasing pressure within them and when ventricle walls relax reducing pressure within ventricles

Question 40

Where are the pocket valves?

Answer 40

in veins that occur throughout the venous system

Question 41

What do the pocket valves ensure?

Answer 41

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

Question 42

What are the valves made up of?

Answer 42

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

Question 43

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

Answer 43

they move apart to let blood pass between cusps

Question 44

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

Answer 44

blood collects within 'bowl' of cusps | this pushes them together to form tight fit that prevents passage of blood

Question 45

What sort of circulatory system do mammals have?

Answer 45

closed circulatory system

Question 46

What does it mean to have a closed circulatory system?

Answer 46

blood confined to vessels

Question 47

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

Answer 47

pressure within them to be maintained + regulated

Question 48

What is cardiac output?

Answer 48

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

Question 49

What unit is cardiac output usually measured in?

Answer 49

dm3min-1

Question 50

What two factors does cardiac output depend on?

Answer 50

``` heart rate (rate at which heart beats) stroke volume (volume of blood pumped out at each beat) ```

Question 51

What is the equation for cardiac output?

Answer 51

heart rate * stroke volume