3.2 Transport in animals

Question 1

What is a single circulatory system?

Answer 1

The blood passes through the heart once per cycle. E.g. Fish

Question 2

What is a double circulatory system?

Answer 2

The blood passes through the heart twice per cycle. E.g. Mammals

Question 3

What is an open circulatory system?

Answer 3

The blood fluid circulates through the body cavity. This is called a haemocoel (blood space).

Question 4

What is a closed circulatory system?

Answer 4

The blood never gets out of the body cavity - it is confined to the blood vessels.

Question 5

How are veins specialised?

Answer 5

Wide lumen; low pressure
Thin wall; less elastic and less muscular
Valves (semilunar); prevent backflow
Deoxygenated blood to heart from tissues; except pulmonary vein from lungs
Non-pulsatile; smooth flow of blood

Question 6

How are arteries specialised?

Answer 6

Narrow lumen; high pressure
Highly elastic; expand and recoil
Thick muscular wall; to withstand force (more elastic fibres)
No valves; except aortic and pulmonary semilunar at the start
Oxygenated blood from heart; except pulmonary artery to lungs
Pulsatile blood flow

Question 7

How are capillaries specialised?

Answer 7

Capillaries have very thin walls. They allow exchange of materials between the blood and cells of tissues via the tissue fluid.
The walls consist of a single layer of flattened endothelial cells that reduces the diffusion distance for the materials being exchanged.
The lumen is very narrow - diameter is the same as a red blood cell. This ensures they are squeezed as they pass along the capillaries - this helps them give up their oxygen.

Question 8

Why is cardiac muscle multinucleated?

Answer 8

Because they are repair tissue so mitosis has to happen faster.

Question 9

Why does cardiac muscle have intercalated discs?

Answer 9

Between each muscle cell so that they can have rapid ion diffusion. They pass electrical waves rapidly between cells which is helped by the branching so that they all contract at once (almost)

Question 10

Why does cardiac muscle have lots of mitochondria?

Answer 10

Lots of ATP release for contraction.

Question 11

What is good about cardiac muscle having a long refractory period?

Answer 11

It has a recovery time so it can continue heating without tiring.

Question 12

Cardiac cycle: Atrial systole

Answer 12

Atria contract, ventricles relax, blood goes from the atria to the ventricles, bicuspid and tricuspid valves are open, semilunar valves are closed.

Question 13

Cardiac cycle: Ventricular systole

Answer 13

Ventricles contract, atria relax, blood goes from ventricles to pulmonary artery and aorta, semilunar valves are open, bicuspid and tricuspid valves are closed.

Question 14

Cardiac cycle: Diastole

Answer 14

No contraction, atria and ventricles relax, blood is going into the atria from the pulmonary veins and vena cava (due to gravity), valves in the pulmonary vein and vena cava are open, semilunar valves are closed (Bicuspid and tricuspid are majoritively closed.

Question 15

What is the cardiac cycle controlled by?

Answer 15

Electrical activity

Question 16

What is a node?

Answer 16

Collection of nervous fibres that creates an electrical impulse.

Question 17

What is the sino-atrial node?

Answer 17

It is like the pacemaker. It sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls. It causes the right and the left atria to contract at the same time.

Question 18

What happens due to the non-conducting collagen tissue that stops electrical waves passing from the atria to ventricles?

Answer 18

The waves of electrical activity are transferred from the sino-atrial node to the atrioventricular node. It is responsible for passing the waves onto a bundle of His (a group of muscle fibres that is responsible for conducting the waves to purkyne tissue.)

Question 19

What does the purkyne tissue do?

Answer 19

Carries the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract simultaneously (from the apex up)

Question 20

What is an electrocardiograph?

Answer 20

It is a machine that records the electrical activity of the heart.
The trace produced by an electrocardiograph is called electrocardiogram.

Question 21

What does the P wave show?

Answer 21

Electrical activity during atrial systole.

Question 22

What is the QRS complex?

Answer 22

Electrical activity during ventricular systole.

Question 23

What is the T wave?

Answer 23

Ventricular repolarisation (recovery of ventricular walls)

Question 24

What is a Q-T interval?

Answer 24

Contraction time.

Question 25

What is a T-P interval?

Answer 25

Filling time.

Question 26

What does an elevation of the ST section indicate?

Answer 26

Heart attack.

Question 27

What does a small and unclear P wave indicate?

Answer 27

Atrial fibrillation

Question 28

What does a deep S wave indicate?

Answer 28

Ventricular hypertrophy (increase in muscle thickness)

Question 29

What is tachycardia?

Answer 29

A heart rate that exceeds the normal resting rate. A resting heart rate over 100 bpm is considered tachycardia in adults.

Question 30

What is brachycardia?

Answer 30

Slow resting heart rate. It is typically under 60 bpm in adults. It can result in fatigue, weakness, dizziness, and fainting.

Question 31

What is atrial fibrillation?

Answer 31

Heart condition that causes an irregular and often abnormally fast heart rate.

Question 32

What is ectopic heartbeat?

Answer 32

Small changes in a heartbeat. These changes lead to extra or skipped heartbeats. The two most common types are PVC (premature ventricular contractions) and PAC (premature atrial contractions.)

Question 33

What is the order that the blood travels through the body, (starting with the pulmonary vein)?

Answer 33

Pulmonary vein, left atrium, bicuspid valve, left ventricle, semi-lunar valve, aorta, body, vena cava, right atrium, tricuspid valve, right ventricle, semi-lunar valve, pulmonary artery, lungs (back to PV).

Question 34

What is the purpose and function of erythrocytes?

Answer 34

Make up 45% of blood volume (named the haemocrit). Transports oxygen from lungs to cells. Contains blood group antigens on the surface of their membranes.

Question 35

What is the purpose and function of leucocytes?

Answer 35

Defence for the body. Lymphocytes - produce antibodies and antitoxins. Phagocytes - engulf and destroy pathogens (microbes)

Question 36

What is the purpose and function of thrombocytes?

Answer 36

Contain enzymes which are released at the site of a cut to convert the soluble blood protein fibrinogen to the insoluble blood protein fibrin. This forms a blood clot which prevents the loss of blood and entry of microorganisms.

Question 37

What is the purpose and function of plasma?

Answer 37

To transport substances around the body as it is a liquid medium.

Question 38

What is tissue fluid and what does it transport?

Answer 38

Fluid which allows exchange of substances between the blood and the cells. It bathes the tissues. Glucose, amino acids, fatty acids, salts, and oxygen are all delivered to the cells by tissue fluid. Carbon dioxide and other waste products are removed from the cell by tissue fluid.

Question 39

What makes up the lymphatic system?

Answer 39

Smallest lymph vessels are the lymph capillaries. Excess tissue fluid passes into lymph vessels. Once inside, it is called lymph. Valves in the lymph vessels stop any lymph going backwards. Lymph gradually moves towards the main lymph which is in the thorax, where it is returned to the blood near the heart.

Question 40

What happens at the arteriole end of the capillaries?

Answer 40

Hydrostatic pressure is higher in the capillaries (due to the decrease in diameter of the vessels) than in the tissue fluid which forces fluid out.

Question 41

What happens at the venuole end of the capillaries?

Answer 41

Oncotic pressure is high due to plasma proteins lowering the water potential in the capillaries. This means that water re-enters the capillaries from the tissue fluid.

Question 42

How does haemoglobin transport oxygen?

Answer 42

Each polypeptide chain has a haem group which contains iron ions. It has a high affinity for oxygen. Oxygen binds to the iron ions to form oxyhaemoglobin, which is a reversible reaction.

Question 43

What happens when partial pressure of oxygen is high (in relation to the oxygen dissociation curve)?

Answer 43

Hb has a high affinity for oxygen so it has a high saturation of oxygen.

Question 44

What happens when partial pressure of oxygen is low (in relation to the oxygen dissociation curve)?

Answer 44

Hb has a low affinity for oxygen which means that it releases oxygen, causing a low saturation.

Question 45

Why is the oxygen dissociation curve 's' shaped?

Answer 45

When Hb combines with the first oxygen molecule, its shape alters in a way that makes it easier for other molecules to bind. However, the first oxygen molecule is the hardest to bind. The second and third oxygen molecules bind really easily. The fourth oxygen molecule rarely ever binds as there isn't enough time.

Question 46

What is different about fetal Hb compared to adult Hb?

Answer 46

Fetal Hb has a higher affinity for oxygen than adult Hb at the same partial pressure.

Question 47

What is the Bohr effect/Bohr shift?

Answer 47

When carbon dioxide levels increase, the oxygen dissociation curve 'shifts' right showing that more oxygen is released from the blood.

Question 48

What happens to 5% of the carbon dioxide in relation to an erythrocyte?

Answer 48

Doesn't enter, dissolves in plasma.

Question 49

What happens to 10% of the carbon dioxide in relation to an erythrocyte?

Answer 49

Hb + CO2 -> Hb . CO2 which is carbaaminohaemoglobin. It is not bonded, just binded.

Question 50

What happens to 85% of the carbon dioxide in relation to an erythrocyte?

Answer 50

CO2 reacts with H2O which is catalysed by carbonic anhydrase to produce carbonic acid. Carbonic acid splits into hydrogen carbonate (which leaves the erythrocyte) and H+ ions. CL- enters the erythrocyte to neutralise the H+ ions. This is the chloride shift.