Circulatory & lymph system; The respiratory system

Question 1

Do atria have thin or thick walls? Why?

Answer 1

Atria have thin walls because unlike the ventricles, they don’t need to generate as much power to force blood out of the heart chambers.

Question 2

What is the pericardium?

Answer 2

The fluid filled sac that encloses the heart.

Question 3

Describe the functions of the pericardium

Answer 3

The pericardium protects the heart.

The fibrous pericardium on the very outside, helps to anchor the heart to its surrounding structures.

The parietal pericardium in the middle and the visceral pericardium on the inside collect fluid between them, allowing the heart to beat easily and without friction..

Question 4

What affect does fluid accumulation in the pericardium have on the heart?

Answer 4

It puts pressure on the heart, affecting its function.

If left untreated, it could lead to heart failure/death.

Question 5

What are the structures in the cardiac muscle allow the myocardium to function as a single unit?

Answer 5

Intercalated discs (the gap between 2 cardiomyocytes) contain 2 types of cell junctions:

 1. Desmosomes - anchoring junctions that keep the heart from pulling itself apart.
 2. Gap junctions - allow the electric impulses to move from cell to cell so the health beats in sync.

Without gap junctions each cardiac muscle cell would act alone and the heart would be ineffective as a pump.

Question 6

Would you expect cardiac cells to have large or small numbers of mitochondria? Why?

Answer 6

Large.

The heart needs a-lot of energy to pump blood.

Question 7

Explain why the myocardium of the left ventricle is thicker than that of the right ventricle.

Answer 7

The left ventricle is the chamber from which blood is pumped from the heart into systemic circulation. This takes a-lot more force than pumping it into pulmonary circulation like the right ventricle does.

Question 8

Explain the term depolarisation

Answer 8

Electrical activation of the myocardium resulting in less negative charge within the cell.

Question 9

Explain the term repolarisation

Answer 9

Restoring the electrical potential of the heart - more negative charge inside the cell.

Question 10

Why is the SA node known as the “pacemaker” of the heart?

Answer 10

It generates the electrical impulses which triggers a sequence of electrical events to control the normal rate and rhythm of the heart.

Question 11

Describe the sequence of excitation during cardiac conduction.

Answer 11

1. SA node generates impulse.
2. The impulse travels through the atria causing atrial contraction.
3. The impulse reaches the AV node where it is delayed.
4. The impulse travels down the AV bundle (bundle of his).
5. The impulse travels through the left and right bundle branches.
6. The impulse reaches the Perkinje fibres which causes ventricular contraction.

Question 12

What causes atrial contraction?

Answer 12

Atrial depolarisation (electrical event).

P wave.

Question 13

What causes ventricular contraction?

Answer 13

Ventricular depolarisation (electrical event).

QRS wave.

Question 14

What causes ventricular relaxation?

Answer 14

Ventricular repolarisation (electrical event).

T wave.

Question 15

Describe the functions of coronary circulation.

Answer 15

1. Delivers O2 to the myocardium.

Question 16

What are the main coronary arteries and what is their purpose?

Answer 16

1. The left coronary artery - is larger because it supplies the left side of the heart which has more powerful contractions.
2. The right coronary artery supplies the right side of the heart.

Question 17

Explain how the exchange of gasses in the peripheral tissues is achieved

Answer 17

You breathe in O2 and it travels to the alveoli where the walls are thin enough that it can diffuse through the membrane into a nearby capillary via diffusion (O2 concentration is lower is the capillaries).

Question 18

What is the function of the heart valves?

Answer 18

To control the flow of blood through the heart by preventing backflow.

Question 19

What do normal heart sounds sound like?

Answer 19

Lub Dub.

Question 20

Discuss the problems and causes associated with heart murmers.

Answer 20

Heart murmurs are causes by faulty blood flow to the heart. This might include congenital heart disease and heart valve problems.

Problems associated with heart murmurs include shortness of breath, cyanosis, cough, poor appetite and failure to grow normally (in infants).

Question 21

What are heart murmers?

Answer 21

Abnormal heart sounds.

Question 22

Describe the differences between the wall of an artery and the wall of a vein.

Answer 22

Arteries have thicker walls due to a thick tunica media dominated by smooth muscle cells and elastic fibres and an external elastic membrane.

Veins have much thinner walls due the a thinner tunica media with no elastic membrane.

Question 23

What is the functional significance in the difference in thickness between arteries and veins.

Answer 23

Artery walls need to be thicker as they endure exposure to much greater pressure than veins. The thick walls allow them to absorb the pressure created by the ventricles as they pump blood out of the heart.

Veins operate at a low pressure, low speed and possess valves to prevent backflow of blood.

Question 24

Why is it important that arteries can alter their diameter?

Answer 24

Arteries can alter their diameter (vasodilation and vasoconstriction) to allow them to withstand greater pressure.

It also helps to auto regulate blood pressure and allows us to adapt to environmental changes.

Question 25

What is blood pressure?

Answer 25

The pressure exerted by the blood against the walls of arteries.

Question 26

How is blood pressure regulated?

Answer 26

Homeostasis. The medulla oblongata contains a cardiovascular centre which is a groups of neurones taht regulate HR, contractility and blood vessel diameter. There are also cardiovascular centres in the hypothalamus that are active during sympathetic response only. Baroreceptors (sensory neurones) in the walls of blood vessels and atria and pressure sensitive and monitor stretching.

Question 27

What happens to CO, SV, HR, PR (peripheral resistance) and the radius of arterioles when blood pressure increases?

Answer 27

All increase except the radius of arterioles which will decrease.

Question 28

What is mean arterial pressure (MAP)?

Answer 28

The average pressure in the arterial system during 1 cardiac cycle. MAP = CO x Total peripheral resistance.

Question 29

How does the body respond to a drop in blood pressure?

Answer 29

1. The baroreceptor reflex is a rapid response in which noradrenaline release is increased causing vasoconstriction and increased HR. Increased adrenaline release from the adrenal medulla also increases HR. 2. The renin angiotensin aldosterone system causes renin to be released from the kidneys causing aldosterone release which increases water retention and therefore blood volume. This causes increase CO and this, increased BP.

Question 30

What would happen to a person's HR during deep sleep?

Answer 30

Decrease (parasympathetic).

Question 31

What would happen to a person's HR during severe stress?

Answer 31

Increase (sympathetic response).

Question 32

What would happen to a person's HR during dehydration?

Answer 32

Increase - lower blood volume results in lower blood pressure and thus, lower HR.

Question 33

What would happen to a person's HR following the ingestion of large amounts of alcohol?

Answer 33

Increase - alcohol is a vasodilator. Vasodilation reduces blood pressure and HR increases to compensate.

Question 34

What are the major components of blood?

Answer 34

Plasma (55%) Erythrocytes, Leukocytes and platelets (45%).

Question 35

List the major functions of blood.

Answer 35

>Transportation of dissolved gasses, waste, hormones, enzymes, nutrients, plasma proteins and blood cells. >Maintenance of body temperature. >Controls pH. >Removes toxins from the body. >Regulates fluid electrolytes by removing excess salt.

Question 36

State the functions of erythrocytes

Answer 36

>To carry O2 from the lungs to the tissues. >Regulating blood flow and blood pressure via the release of nitric oxide which causes vasodilation. >Erythrocytes contain carbonic anhydrase which catalyses the conversion of CO2 and water to carbonic acid which then transports CO2 in the plasma.

Question 37

What impact would anaemia have on HR and respiration?

Answer 37

Respiratory rate would increase as a result of there not being enough erythrocytes to carry O2. HR would increase to pump the remaining cells around the body faster.

Question 38

List the types of leukocytes in the blood and state the major functions for each.

Answer 38

1. Basophils - release histamines which can cause hypersensitivity reactions (allergies) and asthma attacks. 2. Neutrophils - play a role in acute inflammatory response. 3. Eosinophils - digest bacteria and other pathogens. 4. Monocytes - phagocytic cells. 5. Lymphocytes - predominantly seen in chronic inflammation.

Question 39

State the role of platelets

Answer 39

Platelets play a role in clotting and can be involved in the formation of a thrombus. Platelets only survive for 5-9 days.