15.4

Question 1

what is the cardiac cycle? How many times does that happen per minute? (2)

Answer 1

(1) The sequence of events that is repeated in the heart
(2) typically around 70 times per minute at rest

Question 2

what are the two main phases of the cardiac cycle? (2)

Answer 2

(1) contraction (systole)
(2) relaxation (diastole)

Question 3

The unidirectional flow of blood is maintained by ____(1)____ changes & the action of ____(2)____

Answer 3

(1) pressure
(2) valves

Question 4

Describe what happens during the relaxation of the heart (diastole). (4)

Answer 4

(1) Blood returns to the atria via the pulmonary vein and vena cava.
(2) as the atria fill, the pressure rises, opening the atrioventricular valves,
(3) allowing blood to pass into the relaxed ventricles.
(4) the semi lunar valves in the aorta in the pulmonary artery are closed

Question 5

The sound of a heartbeat is described as “dub lub” or “lub dub”. What causes the “dub” sound of the heartbeat? (1)

Answer 5

The closing of the semi-lunar valves in the aorta and pulmonary artery during ventricular diastole

Question 6

Describe what happens during the contraction of the atria (atrial systole). (3)

Answer 6

(1) The atrial walls contract,
(2) forcing the remaining blood (about 20%) **into the ventricles **
(3) the ventricle walls remain relaxed

Question 7

Describe what happens during the contraction of the ventricles (ventricular systole). (4)

Answer 7

(1) after a short delay, the ventricle walls contract simultaneously.
(2) this increases pressure, forcing the atrioventricular valves shut and preventing the back flow into the atria
(3) the semi lunar valves are then forced open
(4) the blood is pushed into the aorta and pulmonary artery.

Question 8

The sound of a heartbeat is described as “dub lub” or “lub dub”. What causes the “lub” sound of the heartbeat? (1)

Answer 8

The closing of the atrioventricular valves during ventricular systole

Question 9

True or false: atrial and ventricular systole occur simultaneously. Explain (2)

Answer 9

(1) false
(2) atrial systole happens before ventricular systole

Question 10

Why does the left ventricle have a thicker wall than the right ventricle? (2)

Answer 10

(1) It needs to generate a higher pressure to pump blood around the entire body (systemic circulation).
(2) the right ventricle only pumps blood to the nearby lungs (pulmonary circulation).

Question 11

NOTE: if you want to see a visual of the process of the cardiac cycle, check out page 201 for the detailed annotations.

Answer 11

xoxo

Question 12

why are the walls of the ventricles thicker than the walls of the atria? (2)

Answer 12

(1) The walls of the ventricles have to pump blood to the extremities of the body & the lungs,
(2) whereas the atria only pump to the ventricles, which is a shorter distance.

Question 13

What is the primary mechanism that ensures blood flows in the correct direction through the heart and body? (2)

Answer 13

(1) The pressure created by heart muscle.
(2) blood moves from areas of higher pressure to lower pressure

Question 14

How do valves in the cardiovascular system open? (2)

Answer 14

(1) They open when the difference in blood pressure on either side of them
(2) favors the movement of blood in the required direction

Question 15

How do valves in the cardiovascular system close? (2)

Answer 15

(1) they close when pressure differences are reversed,
(2) and blood would tend to flow in the opposite direction to what is desirable

Question 16

What are the 3 types of cardiovascular valves? (3)

Answer 16

(1) atrioventricular valves
(2) semi-lunar valves
(3) pocket valves

Question 17

What is the function of the atrioventricular valves? (3)

Answer 17

(1) they prevent the backflow of blood
(2) from the ventricles into the atria
(3) when the ventricles contract OR when the ventricular pressure exceeds atrial pressure

Question 18

What is the function of the semi-lunar valves? (3)

Answer 18

(1) they prevent the backflow of blood
(2) from the aorta and pulmonary artery into the ventricles
(3) when the elastic walls of these vessels recoil OR when creating higher pressure in the vessels than in the ventricles

Question 19

where are pocket valves found? (1)

Answer 19

in veins throughout the venous system

Question 20

what is the function of pocket valves? (2)

Answer 20

(1) they ensure that when veins are squeezed (e.g. by skeletal muscle contraction)
(2) blood flows back into the heart rather than away from it

Question 21

describe the basic structure of cardiovascular valves. (4)

Answer 21

(1) made up of cusps (that can be 2 or 3),
(2) which are tough, but flexible, fibrous tissue that are cup-shaped
(3) the cusps are attached to string-like tendons
(4) and these tendons are attached to pillar muscles

Question 22

How do the cusps of a valve allow blood to pass through? (2)

Answer 22

(1) When pressure is greater on the convex side of the cusps,
(2) they move apart allowing blood to flow between them

Question 23

How do the cusps of a valve prevent the backflow of blood? (3)

HINT: check sticky note on page 203

Answer 23

(1) when pressure is greater on the concave side of the cusps,
(2) blood collects within the “bowl” of the cusps,
(3) pushing them tighter together to form a tight seal

Question 24

What structures prevent the atrioventricular valves from INVERTING due to the high pressures in the ventricles? (2)

inverting = key word

Answer 24

(1) string-like tendons attached to
(2) the pillars of muscle in the ventricle wall

Question 25

Define cardiac output. (1)

Answer 25

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

Question 26

What are the two factors that determine cardiac output? (2)

Answer 26

(1) **Heart rate** (the rate at which the heart beats) (2) **Stroke volume** (volume of blood pumped out at each beat)

Question 27

write the formula for calculating cardiac output. (1)

Answer 27

cardiac output = heart rate x stroke volume

Question 28

The cardiac muscle is myogenic, not neurogenic. What does that mean? (1)

Answer 28

its **contraction is initiated from within the muscle itself** rather than by the nervous impulses from outside

Question 29

What is the sinoatrial node (SAN)? (2)

Answer 29

(1) a distinct **group of cells** within the **wall of the right atrium**, (2) where the **initial stimulus** for **heart contraction originates**

Question 30

What is another name for the SAN and why? (2)

Answer 30

(1) the **pacemaker**, (2) because it has a **basic rhythm of stimulation** that **determines the beat of the heart**

Question 31

Describe the first step in the control of the cardiac cycle after the SAN initiates a signal. (2)

Answer 31

(1) a **wave of electrical activity spreads out from the SAN** across **both atria**, (2) causing them to **contract**

Question 32

What prevents the wave of electrical activity from directly passing from the atria to the ventricles? (1)

Answer 32

a **layer of non-conductive tissue** called the **atrioventricular septum**

Question 33

what is the atrioventricular node (AVN)? (2)

Answer 33

(1) A **group of cells** located **between the atria** (2) that the **wave of electrical activity passes** through **after the atria contract**

Question 34

What is the function of the AVN in controlling the cardiac cycle? (2)

Answer 34

(1) after a **short delay**, it **conveys the wave of electrical activity** (2) **between the ventricles** along the **bundle of His**

Question 35

What is the bundle of His? (2)

Answer 35

(1) a series of **specialized muscle fibers ** (2) that **conduct a wave of electrical activity** from the **AVN between the ventricles**

Question 36

Where does the bundle of his conduct the wave of electrical activity? (2)

Answer 36

(1) **through the atrioventricular septum to the base of the ventricles** (2) where it **branches into smaller fibers**, called the **Purkinje fibers** (these make up the **purkyne tissues**

Question 37

What happens after the wave of electrical activity is released from the small fibers of the bundle of His? (2)

Answer 37

(1) the **ventricles contract quickly** at the **same time**, (2) **from the apex** of the heart **upwards**

Question 38

What type of circulatory system do mammals have? What does this allow? (2)

Answer 38

(1) a **closed** circulatory system, where **blood is confined to vessels** (2) this allows the **pressure** within them to be **maintained & regulated**

Question 39

NOTE: Don't simply state that the role of the sinoatrial node SAN is to act as a pacemaker. The SAN produces a **wave of electrical activity** that causes both atria to **contract** followed by the ventricles. The SAN **initiates the heartbeat.**

Answer 39

xoxo

Question 40

NOTE: Do not mix up **cardiac output** and **pulmonary ventilation**. Whilst **both measure volumes**, the first involves **blood and the heart (cardiac)** and the second involves **air and the lungs (pulmonary)**

Answer 40

xoxo

Question 41

NOTE: to visualise the process of how the cardiac cycle is controlled, check figure 4 on page 203

Answer 41

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Question 42

NOTE: to visualise the process of how the valves function, check figure 2 on page 202

Answer 42

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Question 43

IMPORTANT NOTE: check the graph on page 204 to see the pressure and volume changes in the left side of the heart during the cardiac cycle.

Answer 43

SUPPORT: - **Pressure and volume within a closed container are inversely related**. When pressure increases, volume decreases, and vice versa. - **Blood**, like all fluids, moves from a region where its pressure is greater to one where it is lower, that is, it **moves down a pressure gradient**

Question 44

Look at RP 4, the effect of exercise on heart rate, on page 205 or the practical handbook. Suggest why the pulse is only taken for 15 seconds. (1)

Answer 44

taking the pulse for longer could result in **miscounting & lead to inaccuracies**

Question 45

Look at RP 4, the effect of exercise on heart rate, on page 205 or the practical handbook. Use your knowledge of the role of the circulatory system to explain why the heart rate increases in response to exercise. (3)

Answer 45

(1) as **muscles work harder** there is **increased demand for energy** (ATP). (2) Most ATP comes **from aerobic respiration**, which **requires oxygen**. (3) **Heart rate increases** to **deliver more oxygen** to **respiring cells**

Question 46

Look at RP 4, the effect of exercise on heart rate, on page 205 or the practical handbook. Explain why a 'pre-assessment' test is necessary before carrying out the step test. (2)

Answer 46

(1) subjects may have **coronary heart disease**. (2) The **increased heart rate during a step test** might **result in a myocardial infarction** (a heart attack).