Unit 3 - Mass Transport In Animals

Question 1

Why have animals developed a circulatory system?

Answer 1

All cells need a plentiful supply of oxygen that needs to be delivered rapidly to all cells for aerobic respiration. Diffusion is too slow a process therefore animals have developed a circulatory system based on blood transport in blood vessels.

Question 2

Definition of mass flow?

Answer 2

The bulk movement of liquids (and gases) due to a pressure difference.

Question 3

What are closed systems and why are they more efficient than open systems?

Answer 3

-Closed systems are liquid within tubes, I.e. liquid within tubes.
-It is easier to generate and maintain a pressure difference.

Question 4

Direction that blood moves in?

Answer 4

-Down a pressure gradient.
-Arteries, capillaries, veins.

Question 5

Why do mammals have a double circulatory system?

Answer 5

It refers to the fact that blood passes twice through the heart for each complete circuit of the body.

Question 6

Heart?

Answer 6

Made up from cardiac muscle which contracts to pump blood around the body.

Question 7

Vena cava?

Answer 7

The vein returning deoxygenated blood to the right atrium of the heart.

Question 8

Pulmonary artery?

Answer 8

Take’s deoxygenated blood from the right ventricle to the lungs.

Question 9

Pulmonary vein?

Answer 9

Returns oxygenated blood from the lungs to the left atrium.

Question 10

Aorta?

Answer 10

Main artery taking blood from the heart to the organs.

Question 11

Coronary arteries?

Answer 11

Branch from the aorta and take blood to the muscle of the heart. The heart muscle needs its own blood supply for rapid delivery of oxygen and glucose.

Question 12

Kidney?

Answer 12

This organ is important for excretion of nitrogenous waste and for osmoregulation (maintaining the correct water potential in the blood).

Question 13

Renal artery?

Answer 13

Takes oxygenated blood to the kidney.

Question 14

Renal vein?

Answer 14

Takes deoxygenated blood away from the kidney.

Question 15

Structure of haemoglobin?

Answer 15

-A protein with a quaternary structure.
-It is composed of 4 sub units, each containing a haem group.
-Each haem group contains an iron ion, which is what allows oxygen to bind due to its negative charge.
-Each haem group can combine with 1 oxygen molecule.
-Each haemoglobin molecule can combine with 4 oxygen molecules (8 oxygen atoms).

Question 16

Reaction for the uptake of oxygen by haemoglobin?

Answer 16

Haemoglobin + Oxygen = Oxyhaemoglobin
ITS A REVERSIBLE REACTION!!!!

Question 17

What is % saturation of the haemoglobin?

Answer 17

The amount of oxygen combined.

Question 18

Definition of partial pressure (p)?

Answer 18

The amount of a particular gas in a mixture of gases or a solution.

Question 19

Oxygen dissociation curve graph?

Question 20

What does the graph show?

Answer 20

The more oxygen there is in the blood, the more the oxygen is taken up by haemoglobin. The haemoglobin becomes saturated.
The lower the amount of oxygen in the blood, the less oxygen is taken up by the haemoglobin. The haemoglobin becomes less saturated.

Question 21

What does loading (association) mean?

Answer 21

When oxygen is taken up by haemoglobin, normally at the lungs.
Higher pO2-more oxygen loaded by haemoglobin.

Question 22

What does unloading (dissociation) mean?

Answer 22

When oxygen is released from haemoglobin, normally to be used in respiring tissues.
Lower pO2-less oxygen loaded by haemoglobin.

Question 23

Why is the curve sigmoid shaped?

Answer 23

This is because when the first oxygen molecule binds to the haemoglobin, this changes the tertiary structure of haemoglobin which uncovers another haem group for Oxygen to bind to. This makes it easier for the next oxygen molecule to combine with the haemoglobin.

Question 24

pO2 in the lungs?

Answer 24

In the alveoli capillaries in the lungs, the pO2 is higher and the haemoglobin becomes saturated as oxygen loads/associates as the red blood cells pass through the pulmonary capillaries.

Question 25

pO2 in the tissue?

Answer 25

The red blood cells now pass to the capillaries in body tissues. In the tissues the pO2 is lower due to respiring tissues, so the haemoglobin unloads/dissociates the oxygen to respiring tissues.

Question 26

What is the effect of increased respiration on oxygen dissociation?

Answer 26

1) Cells aerobically respire more quickly.
2) Respiration uses more of the O2 surrounding the tissue.
3) This reduces the pO2 to a level lower than normal.
4) The haemoglobin will dissociate more of the O2 (less saturated) and more oxygen will be released from the haemoglobin to respiring cells.

Question 27

Definition of affinity?

Answer 27

The ability of haemoglobin to bind/associate with oxygen.

Question 28

The Bohr Shift graph?

Question 29

Describe why the Bohr shift happens?

Answer 29

The affinity of haemoglobin for oxygen is lowered by increasing carbon dioxide concentration. If CO2 levels increase the saturation of haemoglobin decreases. This causes the haemoglobin-oxygen dissociation curve to shift to the right called the Bohr shift.

Question 30

Graph showing the 3 types of haemoglobin?

Question 31

A?

Answer 31

This type of haemoglobin is found in adult humans and many other species that live on land at sea level.

Question 32

B?

Answer 32

This is found in species that live in environments where the environmental pO2 is lower (high altitude, at the bottom of lakes) or in foetal haemoglobin.
Curve shifted to left:
-Environment has a lower pO2
-Haemoglobin - fully saturated at a lower pO2
-rapidly unloads its oxygen when the haemoglobin passes into the tissues

Question 33

C?

Answer 33

This form of haemoglobin has a curve shifted to the right and is characteristic of species that have a high metabolic/respiration rate. The haemoglobin has a lower affinity for oxygen and will therefore unload its oxygen much more readily to respiring tissues.

Question 34

Structure of the heart?

Question 35

Flow of blood around the body?

Answer 35

1) Deoxygenated blood returns from the body in the vena cava (vein) and enters the right atrium.
2) The blood then passes, via an atrio-ventricular valve into the right ventricle and out, via the semi-lunar valve, into the pulmonary artery.
3) The blood now passes through the lungs and returns to the left atrium via the pulmonary vein.
4) The blood passes through a second atrioventricular valve into the left ventricle and then through the semi-lunar valve into the aorta and then onto the body tissues.

Question 36

How does blood move?

Answer 36

Contraction of the heart muscle generates a pressure in the blood in the atria and ventricles. This pressure pushes blood through blood vessels. A large pressure is needed to push the blood through the arteries and capillaries. The blood moves due to the pressure difference between the pressure in the heart (high) and the pressure in blood vessels (low).

Question 37

Why is the wall of the left ventricle much thicker than that of the right?

Answer 37

To provide a greater contraction force as the left ventricle is pushing blood through a much larger number of capillaries around the body, but the right ventricle is only pushing blood through the pulmonary capillaries.

Question 38

Why are the walls of the atria much thinner than the ventricles?

Answer 38

As they only need to generate a small pressure to pump the blood from the atrium to the ventricle.

Question 39

What is the job of the valves?

Answer 39

To ensure that the blood flows in one direction through the heart. They do this by only opening in one direction. They open and close due to pressure differences on either side of the valve.

Question 40

When do atrio-ventricular valve open and close?

Answer 40

The open when the pressure in the atria increases above that in the ventricles. They close when the pressure in the atria decreases below that in the ventricles.

Question 41

When do semi-lunar valves open and close?

Answer 41

These open when the pressure in the ventricle increases above that in the aorta and pulmonary artery. They close when the pressure in the ventricle decreases below that in the aorta and pulmonary artery.

Question 42

What is the Cardiac cycle?

Answer 42

This is the sequence of events that leads to the filling and emptying of the heart. After the heart fills with blood, the blood is then pumped into the arteries. The movement is brought about by changes in blood pressure which result from heart muscle contraction.

Question 43

What are the 3 phases of the cardiac cycle?

Answer 43

-Diastole=muscles relax/takes place simultaneously in all chambers/atria will relax before ventricles.
-Atrial systole=atrial muscle contracts.
-Ventricular systole=ventricular muscles contracts.
Atrial and ventricular systole occurs separately in the atria and ventricles. Atria must contact before ventricles.

Question 44

Definition of cardiac output?

Answer 44

It is defined as the volume of blood expelled from (pumped out of) the left ventricle per minute.

Question 45

Definition of stroke volume?

Answer 45

It is the volume of blood expelled from the left ventricle on one heart beat.

Question 46

Definition of heart rate?

Answer 46

It is the number of cardiac cycles (beats) per minute.

Question 47

Cardiac output formula?

Answer 47

CO = SV x HR

Question 48

Role of the artery?

Answer 48

-Transports blood from heart to organ. Blood is under high pressure so the wall is very thick to withstand this pressure.

Question 49

Structure of the artery?

Answer 49

Endothelial layer:
-Layer is only 1 cell thick (endothelial cells)
-Gives a smooth layer which reduces friction + gives smooth flow.
Elastic tissue:
-Contains a large amount of elastic protein fibres.
-Allows wall to stretch as pulse of blood flows past. This stops pressure rising too high.
-Recoils once blood passes. This maintains a pressure on the blood.
-Variations in blood pressure partially smoothed out.
Outer layer:
-Made of fibrous proteins and gives support and strength to wall, helping it to resist damage due to the high pressure of the blood inside.

Question 50

Role of the arterioles?

Answer 50

-Smaller vessels than arteries and connect artery to the capillaries.
-As the vessel diameter is smaller than an artery, there is greater friction between the blood and the vessel wall. This causes a fall in blood pressure.

Question 51

Adaptations of the arterioles?

Answer 51

Structure is the same for an artery apart from:
-The elastic layer is thinner. As the blood pressure is lower, there is less need for the elasticity required to allow the pulse of blood to pass.
-The muscle layer is thicker. The muscle in the arterioles can be contracted to constrict the vessel (vasoconstriction). This reduces flow into the organ. Alternatively, the muscle can be relaxed which causes the vessel to dilate (vasodilation). This allows more blood into the organ.

Question 52

Adaptations of the capillary?

Answer 52

-Wall only has the 1 cell thick endothelial layer.
-This gives a short diffusion pathway for the exchange of materials between blood and the tissue cells.
-Diameter is very small and there is a large number of capillaries. This creates considerable friction and the blood pressure created by the heart is lost as the blood flows through the capillaries.

Question 53

Role of the veins?

Answer 53

These carry blood back to the heart from the tissues. The blood is under low pressure, therefore the vein wall does not need to be thick.

Question 54

Structure of the veins?

Answer 54

-It’s similar to that in the artery, but:
-Muscle layer is very thin. There is no need for vaso-constriction as all the blood is going back to the heart.
-Elastic layer is thin. Pressure is very low and the wall does not need to stretch or recoil.
-The veins have valves to prevent back flow.

Question 55

How is blood moved along the vein?

Answer 55

The blood is moved along the vein by the squeezing action of skeletal muscles when they contract.

Question 56

What is blood flow and pressure like in the arteries?

Answer 56

In the arteries flow is fast and pressure is high and fluctuating.

Question 57

What is blood flow and pressure like in the capillaries?

Answer 57

Friction causes the pressure to fall and speed of flow decreases.

Question 58

What is the role of capillaries?

Answer 58

Gases, nutrients e.g. amino acids and glucose and wastes e.g. urea need to be exchanged between the blood and the tissue. This only occurs at the capillaries.

Question 59

Adaptations of capillaries for gas exchange?

Answer 59

-Very thin walls (only 1 cell thick)
-Narrow diameter (ensures RBC is in contact with wall)
-Wall spaces (there are gaps between the cells of the endothelial cells which allow rapid formation of tissue fluid and white blood cells to pass into tissue spaces)z
-Numerous and branched (increases overall surface area for diffusion).

Question 60

What is tissue fluid?

Answer 60

The cells in the tissue have space around them which is filled with a fluid (tissue fluid).

Question 61

Formation of tissue fluid?

Answer 61

1) The blood has a high hydrostatic pressure. At the arteriole end of the capillary.
2) This forces water and other small molecules e.g. oxygen, amino acids, glucose out of the capillaries.
3) This is called tissue fluid - exchange of gases, nutrients e.g. glucose and waste products e.g. urea occurs between the tissue fluid and the cells.
4) Large plasma proteins remain in the blood as they are too big to leave the capillary.
5) This lowers the water potential inside the capillary, at the venule end of the capillary.
6) Water moves back into the capillary by osmosis.
7) Excess tissue fluid is absorbed by lymph vessels.

Question 62

How does the lymphatic system work?

Answer 62

-The net force pushing liquid out at the start of the capillary is greater than the net force pulling back in at the end of the capillary.
-Therefore, more liquid leaves the capillary than re-enters. This fluid cannot stay in the tissue spaces otherwise swelling (oedema) occurs.
-The fluid drains into tubes known as lymphatic vessels.
-These merge together and form a network running through the body.
-These eventually empty back into the blood stream in veins in the neck.
-The fluid is moved through these vessels in a similar manner to movement of blood in the veins.