Cardiovascular system

Question 1

What factors affect stroke volume?

Answer 1

Venous return
Elasticity of cardiac fibres.

Question 2

How does venous return affect stroke volume?

Answer 2

This is the volume of blood returning to the right side of the heart via the vena cava.
If this increases, stroke volume also increases (Starling’s law).

Question 3

How does elasticity of cardiac fibres affect stroke volume?

Answer 3

This is concerned with the degree of stretch of cardiac tissue during diastole.
The more stretch, the greater the force of contraction.
Greater force of contraction can increase ejection fraction - Starling’s Law.

Question 4

What is Starling’s law?

Answer 4

Increased venous return - greater diastolic filling of the heart - cardiac muscle stretched - greater force of contraction - increased ejection fraction.

Question 5

What is the heart rate in an untrained performer vs trained?

Answer 5

Trained: has a lower resting and a higher maximum heart rate.
Their heart rate range is higher.

Question 6

What does heart rate do in maximal and sub-maximal exercise?

Answer 6

Both:
Anticipatory rise
Sharp rise mainly due to anaerobic work.
(Maximal only) Heart rate continues to rise due to maximal workloads stressing the anaerobic systems.
(Submaximal only) Steady state as the athlete is able to meet the oxygen demand with the oxygen supply.
Both: Rapid decline in heart rate as soon as exercise stops.
Slower recovery as body systems return to resting levels.
Heart rate needs to remain elevated to rid the body of waste products.

Question 7

What are stroke volume, heart rate and cardiac output values?

Answer 7

During exercise, in untrained person: 120ml x 202bpm = 24.24L
Trained person: 170ml x 202 = 34.34L.
At rest, untrained person: 70ml x 72 = 5.04L
Trained person: 84ml x 60 = 5.04L.

Question 8

How does stroke volume respond to exercise?

Answer 8

Stroke volume increases as exercise intensity increases.
But only up to 40-60% of maximum effort.
After this, stroke volume plateaus.
The ventricles do not have as much time to fill with blood, so can not pump as much out.

Question 9

What is heart disease?

Answer 9

It occurs when the coronary arteries become blocked or start to narrow by build-up of fatty deposits (athereroma).
This is called atheroscolerosis.

Question 10

What causes heart disease?

Answer 10

High blood pressure
High cholesterol levels
Lack of exercise
Smoking

Question 11

What effect does heart disease have on the body?

Answer 11

As the coronary arteries narrow they are unable to deliver enough oxygen to the heart, causing pain and discomfort - angina.
If a piece of artheroma breaks off in the coronary arteries it can cause a blood clot which forms a blockage.
This can cut off oxygenated blood supply to the heart muscle, resulting in a heart attack.

Question 12

How can heart disease be prevented?

Answer 12

Exercise keeps the heart healthy and more efficient.
It can pump more blood around the body as exercise causes hypertrophy, resulting in increased stroke volume.
Regular exercise also maintains the flexibility of blood vessels, ensuring good blood flow, normal blood pressure and low cholesterol levels.

Question 13

What is high blood pressure?

Answer 13

Blood pressure is the force exerted by the blood against the blood vessel wall.
High blood pressure puts extra strain on the arteries and heart.
Considered to be > 140/90 mmHg, while normal bp is between 90/60 and 120/80.

Question 14

What effect does high blood pressure have on the body?

Answer 14

It puts increased strain on the arteries and heart.
Left untreated, it increases the risk of heart attack, heart failure, kidney disease, stroke or dementia.

Question 15

How is high blood pressure prevented?

Answer 15

Regular aerobic exercise.
It lowers both systolic and diastolic pressure by up to 5-10 mmHg.
This reduces the risk of a heart attack by up to 20%.

Question 16

What are Low Density Lipoproteins?

Answer 16

LDL transport cholesterol in the blood by the tissues and are classed as bad cholesterol as they are linked to increased risk of heart disease.

Question 17

What are High Density Lipoproteins?

Answer 17

HDL transport excess cholesterol in the blood back to the liver where it is broken down.
It’s ‘good’ cholesterol as it lowers the risk of heart disease.

Question 18

What effect does cholesterol have on the body?

Answer 18

High cholesterol levels can increase the risk of heart disease and strokes, as it can build up in the arteries and block them.

Question 19

What are strokes?

Answer 19

It occurs when the blood supply to part of the brain is cut off.
This causes damage to the brain cells so they start to die.
This can lead to brain injury, disability and sometimes death.

Question 20

What are ischaemic strokes?

Answer 20

Most common, occur when a blood clot stops the blood supply.

Question 21

What are haemorrhagic strokes?

Answer 21

Occur when a weakened blood vessel supplying blood to the brain bursts.
High blood pressure often weakens blood vessels.

Question 22

How can strokes be prevented?

Answer 22

Regular exercise can help lower blood pressure and help maintain a healthy weight.
These can reduce the risk of a stroke by 27%.

Question 23

What is cardiovascular drift?

Answer 23

A progressive decrease in stroke volume and arterial blood pressure, and a progressive rise in heart rate.
It occurs during prolonged exercise after 10 minutes, in a warm environment, despite the intensity of exercise remaining the same.

Question 24

Why does cardiovascular drift occur?

Answer 24

When we sweat, a portion of the lost fluid comes from the plasma volume.
This decrease in plasma volume means the blood becomes more viscous and will reduce venous return and stroke volume.
Heart rate increases to compensate and maintain a higher cardiac output, to create more energy to cool the body down.

Question 25

How can cardiovascular drift be minimised?

Answer 25

Maintaining high fluid consumption before and during exercise.

Question 26

What are blood pressure readings?

Answer 26

BP is measured at the brachial artery in the upper arm.
At rest, is typically 120/80 millimetres of mercury (mmHg).
It is mainly dependent on the distance of the blood vessel from the heart.

Question 27

How is venous return affected by exercise?

Answer 27

At rest, up to 70% of the total volume of blood is contained in the veins.
This means that a large amount of blood can be returned to the heart when needed.
During exercise, venous return increases, which increases stroke volume.

Question 28

Why are there venous return mechanisms?

Answer 28

The pressure of the blood in the large veins is very low which makes it difficult to return blood to the heart.
The large lumen of the vein offers little resistance to blood flow.

Question 29

What is the skeletal muscle pump?

Answer 29

When muscles contract and relax they change shape.
This change in shape means that the muscles press on the nearby veins and cause a pumping effect, squeezing blood towards the heart.

Question 30

What is the respiratory pump?

Answer 30

When muscles contract and relax during breathing in and out, pressure changes occur in the thoracic and abdominal cavities.
These changes compress the nearby veins and assist in blood return to the heart.

Question 31

What are pocket valves?

Answer 31

Valves ensure blood only flows in the veins in one direction.
Once the blood has passed through the valves, they close to prevent the blood flowing back.

Question 32

What factors aid in venous return?

Answer 32

A very thin layer of smooth muscle in the walls of the veins helps squeeze the blood back towards the heart.
Gravity helps the blood return to the heart from the upper body.
The suction pump action of the heart.

Question 33

How does blood pressure impact venous return?

Answer 33

When systolic pressure increases, venous return increases.
When systolic pressure decreases, venous return decreases.

Question 34

How is oxygen transported?

Answer 34

During exercise, when oxygen diffuses into the capillaries, 3% dissolves into the plasma and 97% forms oxyhaemoglobin.
This occurs when the partial pressure of oxygen in the blood is high.
At the tissues, oxygen is released from oxyhaemoglobin due to the lower pressure of oxygen there - oxyhaemoglobin dissociation.
In the muscle, the myoglobin stores the oxygen for the mitochondria until used by the muscles.

Question 35

How do baroreceptors work?

Answer 35

They contain nerve endings that respond to the stretching of the arterial wall caused by changes in blood pressure.
An increase above or decrease below the set point for blood pressure send signals to the medulla.
An increase in arterial pressure causes an increase in the stretch of the baroreceptor sensors and decreases heart rate, and vice versa.

Question 36

How do baroreceptors change during exercise?

Answer 36

At the start of exercise, the baroreceptor set point increases, so heart rate does not slow down and negatively affect performance.

Question 37

How does pressure gradient between the right atrium and the vena cava impact venous return?

Answer 37

Venous return is determined by pressure gradient.
Venous pressure - right atrial pressure divided by venous vascular resistance.
The blood pressure in both the right atrium and the peripheral veins is normally very low, so that the pressure driving venous return from the peripheral veins to the heart is also relatively low.
Small changes of blood pressure in the right atrium or peripheral veins can largely change the pressure gradient, and significantly affect venous return.

Question 38

What is the oxyhaemoglobin dissociation curve?

Answer 38

The partial pressure of oxygen in the lungs is higher, haemoglobin is almost completely saturated with oxygen.
In the tissues, the partial pressure is lower, so haemoglobin gives up some of its oxygen to the tissues - up to 23%.

Question 39

What is the Bohr shift?

Answer 39

During exercise, the curve shifts to the right because when the muscles require more oxygen, the dissociation of oxygen from haemoglobin in the blood capillaries to the muscle tissue occurs more readily.

Question 40

Which factors are responsible for the Bohr shift?

Answer 40

Increase in blood temperature - oxygen dissociates from haemoglobin more readily.
Partial pressure of carbon dioxide increases, causing oxygen to dissociate faster.
pH - more carbon dioxide will lower the pH in blood, causing oxygen to dissociate quicker.

Question 41

What is the vascular shunt mechanism?

Answer 41

The redistibution of blood flow to areas where it is most needed /cardiac output.
During exercise, the skeletal muscles need more oxygen.

Question 42

Why is redistribution of blood important?

Answer 42

Used to increase the supply of oxygen to the working muscles.
Remove waste products from the muscles, such as carbon dioxide and lactic acid.
Ensure more blood goes to the skin during exercise to regulate body temperature and get rid of heat through radiation, evaporation and sweating.
Directs more blood to the heart as it is a muscle and requires extra oxygen during exercise.

Question 43

What are the measurements of cardiac output to places during vigorous exercise and rest?

Answer 43

Skeletal muscle: 80-85% vs 15-20%.
Vital organs: 15-20%, mainly the brain vs 80-85%.

Question 44

Why is it important to not eat before competition?

Answer 44

Sports performers should not eat less than an hour before a competition as a full gut would result in more blood being directed to the stomach instead of the working muscles.
This would have a negative effect on performance as less oxygen is being made available.
Blood flow to the brain must remain constant to ensure brain function.

Question 45

How does redistribution of blood flow occur?

Answer 45

The vasomotor centre, in the medulla oblongata of the brain, controls blood flow and pressure.
When chemoreceptors detect chemical changes, they stimulate the vasomotor centre, which redistributes blood through vasodilation and vasoconstriction.
During exercise, vasodilation will occur in the arterioles supplying the working muscles, increasing blood flow and oxygen supply.

Question 46

How does redistribution of blood occur by the sympathetic nerves?

Answer 46

When stimulation of the sympathetic nerves located in the blood vessel walls increases, vasoconstriction occurs and blood flow reduces so it can be redistributed to the other parts of the body such as the muscles.
When stimulation by the sympathetic nerves decreases, vasodilation occurs and increases blood flow to that part.

Question 47

What are pre-capillary sphincters?

Answer 47

They are tiny rings of muscle located at the opening of capillaries.
When they contract, blood flow is restricted through the capillary and when they relax, blood flow is increased.
During exercise, the capillary networks supplying skeletal muscle will have relaxed pre-capillary sphincters to increase blood flow and therefore saturate the tissues with oxygen.

Question 48

What is arterio-venous difference?

Answer 48

A-VO2 difference.
The difference between the oxygen content of the arterial blood arriving at the muscles and the venous blood leaving the muscles.

Question 49

How does A-VO2 difference change during exercise?

Answer 49

At rest, it is low as not much oxygen is required by the muscles.
But during exercise, more oxygen is needed from the blood for the muscles so the difference is high.
This increase will affect gaseous exchange at the alveoli so more oxygen is taken in and more carbon dioxide is removed.
Training also increases the arterio-venous difference as trained performers can extract greater amounts of oxygen from the blood.