Transport in Animals

Question 1

What is the difference between how unicellular and multicellular organisms get substances into them?

Answer 1

Unicellular organisms rely on diffusion as they are thin and have a higher surface area-to-volume ratio.
Multicellular organisms rely on transport systems as they are thick and have a lower surface area-to-volume ratio.

Question 2

Why do multicellular organisms need transport systems?

Answer 2

• They have a low surface area to volume-ratio
• They have a higher metabolic rate
• They are very active, meaning a larger number of cells are respiring very quickly and therefore need a constant supply of oxygen and glucose

Question 3

What is the transport system in mammals?

Answer 3

The circulatory system

Question 4

What is the difference between a single circulatory system and a double circulatory system?

Answer 4

Single: blood only passes through the heart once for each complete circuit of the body (Fish)
Double: Blood passes through the heart twice for each complete circuit of the body (Mammals)

Question 5

What is the single circulatory system in fish?

Answer 5

The heart pumps blood to the gills where it is oxygenated and then on through the rest of the body in a single circuit and back to the heart.

Question 6

What is the double circulatory system in mammals?

Answer 6

The right side of the heart pumps blood to the lungs where it is oxygenated. It then is returned to the left side of the heart, which pumps it to the rest of the body. When it returns to the heart, it enters the right side again.

Question 7

What is the pulmonary system and systemic system?

Answer 7

The pulmonary system is the system that sends blood to the lungs, from the heart and back.
The systemic system is the system that sends blood to the rest of the body and back to the heart.

Question 8

What is an advantage of the circulatory system in mammals?

Answer 8

The heart can give the blood an extra push between the lungs and the rest of the body. This makes blood travel faster, so oxygen is delivered to the tissues more quickly.

Question 9

What is the difference between closed and open circulatory systems?

Answer 9

Closed: The blood is enclosed inside the blood vessels (Vertebrates)
Open: The blood isn’t enclosed in blood vessels all the time. Instead it flows freely through the body cavity (Invertebrates)

Question 10

What is the passage of blood in a closed circulatory system?

Answer 10

• The heart pumps blood into arteries which branch out into millions of capillaries
• Substances diffuse from the blood in the capillaries into the body cells, but the blood stays inside the vessels as it circulates
• Veins take the blood back to the heart

Question 11

What is the passage of blood in an open circulatory system?

Answer 11

• The heart is segmented. It contracts in a wave, starting from the back, pumping the blood into a single main artery
• The main artery opens up into the body cavity
• The blood flows around the organs, gradually making its way back to the heart segments through a series of valves
  (blood doesn’t transport oxygen)

Question 12

What are arteries?

Answer 12

Arteries carry blood from the heart to the rest of the body (away)
- Thick walls
- Muscular walls
- Elastic fibers (help maintain high pressure)
- Folded inner lining/ endothelium (Allow expansion)
All carry oxygenated blood except the pulmonary artery

Question 13

What are arterioles?

Answer 13

They are a much smaller form of artery
- Layer of smooth muscle (allow them to expand or contract and regulate the amount of blood flowing to tissues)
- Less elastic tissue than arteries

Question 14

What are capillaries?

Answer 14

They are the smallest of the blood vessels
- substances like glucose and oxygen are exchanged between cells and capillaries
- adapted for diffusion (1 cell thick etc.)

Question 15

What are venules?

Answer 15

They are a smaller form of vein
- They have very thin walls that can contain some muscle cells
- They join together to form veins

Question 16

What are Veins?

Answer 16

Veins take blood back to the heart (IN)
- low pressure
- wider lumen
- little elastic and muscle tissue
- contain valves to prevent backflow of blood
- blood flow is helped by the contraction of the body muscles surrounding them.
They all contain deoxygenated blood, except for the pulmonary veins

Question 17

What is tissue fluid?

Answer 17

Tissue fluid is the fluid that surrounds cells in tissues. It is made from substances that leave the blood plasma but it doesn’t contain red blood cells or big proteins.
Cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it. In a capillary bed, substances move out of the capillaries, into the tissue fluid, by pressure filtration.

Question 18

What is the process of pressure filtration?

Answer 18

• At the start of the capillary bed nearest the arteries the hydrostatic pressure is greater in the capillaries than in the tissue fluid. The difference in pressure forces fluid out of the capillaries and into the spaces around the cells- forming tissue fluid.
• As fluid leaves the capillaries the hydrostatic pressure decreases, so at the end of the capillary bed nearest to the venues the pressure is lower.

Question 19

What is oncotic pressure in pressure filtration?

Answer 19

The oncotic pressure is generated by plasma proteins present in the capillaries which lower the water potential.
- it is lower at the venule end at the capillary bed due to the fluid loss from the capillaries and the high oncotic pressure, this means some water re-enters the capillaries from the tissue fluid at the venule end by osomosis.

Question 20

What is the lymphatic system?

Answer 20

Also involved in the immune system, it is a drainage system for tissue fluid.

Question 21

What is the passage fluid takes through the lymph system?

Answer 21

It enters through the lymph capillaries, where it is called lymph. Valves in the lymph vessels stop the lymph from going backward. lymph moves towards the main lymph vessels in the thorax where it is returned to the blood near the heart.

Question 22

Where are red blood cells found? (B,TF,L)

Answer 22

Only in the blood as it is too big to get through capillary walls into the tissue fluid and the lymph.

Question 23

Where are white blood cells found? (B,TF,L)

Answer 23

In the blood and lymph, but few in tissue fluid as they only enter it when there is an infection

Question 24

Where are platelets found? (B,TF,L)

Answer 24

Only in the blood, unless the tissue fluid or lymph is damaged

Question 25

Where are proteins found? (B,TF,L)

Answer 25

In blood, few in tissue fluid and only antibodies in the lymph as most are too big to get through capillary walls.

Question 26

Where is water found? (B,TF,L)

Answer 26

Water is found in blood, tissue fluid, and lymph. Tissue fluid and lymph have a higher water potential than blood.

Question 27

Where are dissolved solutes found? (B,TF,L)

Answer 27

In blood, tissue fluid, and lymph. Solutes can move freely between blood, tissue fluid, and lymph.

Question 28

What are the functions of either side of the heart?

Answer 28

Left: Pump oxygenated blood to the rest of the body
Right: Pumps deoxygenated blood to the lungs

Question 29

What are the valves in the heart and their function?

Answer 29

Atrioventricular valves: link the atria to the ventricles
Semi-lunar valves: link the ventricles to the pulmonary artery and aorta
They prevent the backflow of blood because:
- they only open one way and whether they are open or closed depends on the relative pressure of the heart chambers
Higher behind: open
Higher in front: closed

Question 30

What is the cardiac cycle?

Answer 30

It is the ongoing sequence of contraction and relaxation of the atria and ventricles and it keeps blood continuously circulating around the body.

Question 31

What are the stages in the cardiac cycle?

Answer 31

1) Ventricles relax, atria contract
2) Ventricles contract, atria relax
3) Ventricles relax, Atria relax

Question 32

What happens to the blood when the ventricles relax and the atria contract?

Answer 32

• The ventricles are relaxed and the atria contract which decreases their volume and increases their pressure
• This pushes the blood into the ventricles through the atrioventricular valves.
• There is a slight increase in ventricular pressure and volume as the ventricles receive the ejected blood from the contracting atria

Question 33

What happens to the blood when the ventricles contract and the atria relax?

Answer 33

• The atria relax and the ventricles contract which decreases their volume and increases their pressure
• The pressure is higher in ventricles than atria which forces the atrioventricular valves shut to prevent backflow.
• The high pressure in the ventricles opens the semi-lunar valves and blood is forced out into the pulmonary artery and aorta

Question 34

What happens to the blood when the ventricles relax and the atria relax?

Answer 34

• The ventricles and the atria both relax.
• The higher pressure in the pulmonary artery and aorta causes the semi-lunar valves to close, preventing backflow
• The atria fill with blood which increases their pressure, this is due to the high pressure in the vena cava and pulmonary vein.
• As the ventricles continue to relax, their pressure falls below the pressure in the atria and it causes the atrioventricular valves to open and the whole process to be repeated.

Question 35

What is cardiac output and how do you calculate it?

Answer 35

It is the volume of blood pumped by the heart per minute.
cardiac output= heart rate x stroke volume

Question 36

What is the stroke volume?

Answer 36

It is the volume of blood pumped during each heartbeat in cm3

Question 37

What does myogenic mean? (cardiac)

Answer 37

Cardiac muscle is myogenic which means it can contract and relax without receiving signals from nerves.

Question 38

What is the process of the heartbeat?

Answer 38

1) The process starts in the sino-atrial node (SAN) which is in the wall of the right atrium
2) The SAN is like a pacemaker as it sets out the rhythm by sending out regular waves of electrical activity to the atrial walls
3) This causes both the right and left atria to contract at the same time
4) A band of non-conducting collagen tissue prevents the waves of electrical activity from being passed from the atria to the ventricles
5) Instead, these waves of electrical activity are transferred from the SAN to the atrioventricular node AVN
6) The AVN is responsible for passing the waves of electrical activity onto the bundle of his. But there is a slight delay before it reacts to make sure the ventricles contract after the atria are empty.
7) The bundle of His is a group of muscle fibers responsible for conducting the waves of electrical activity to the finer muscle fibers in the right and left ventricle walls. (purkyne tissue)
8) This tissue carries the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract simultaneously, from the bottom up.

Question 39

What is an electrocardiograph?

Answer 39

It is a machine that records the electrical activity of the heart. It is used by doctors to check someone’s heart function.
The heart muscle depolarises when it contracts and repolarises when it relaxes. An ECG records these changes in electrical charge using electrodes placed on the chest.

Question 40

What does a normal ECG look like?

Answer 40

The p wave is caused by the contraction of the atria.
The main peak is called the QRS complex and is caused by the contraction of the ventricles.
The T wave is due to the relaxation of the ventricles/
The height of the wave indicates how much electrical charge is passing through the heart- a bigger wave means more electrical charge, so a bigger wave means a stronger contraction.

Question 41

What is tachycardia and bradycardia?

Answer 41

Tachycardia is when the heartbeat is too fast. It is ok during exercise but at rest, it shows the heart isn’t pumping blood efficiently. Bradycardia is when the heartbeat is too slow.

Question 42

What is an ectopic heartbeat?

Answer 42

It is caused by an earlier contraction of the atria than in the previous heartbeats. But it can also be caused by early contraction of the ventricles. Occasional ectopic heartbeat in a healthy person doesn’t cause a problem.

Question 43

What is fibrillation?

Answer 43

It is an irregular heartbeat. The atria or ventricles completely lose their rhythm and stop contracting properly. It can result in anything from chest pain and fainting to lack of pulse and death.

Question 44

What is Haemoglobin?

Answer 44

It is found in red blood cells and it is a large protein with a quaternary structure. It is made up of four polypeptide chains where each chain has a haem group, which contains iron and gives hemoglobin its red color.
Haemoglobin has a high affinity for oxygen and each molecule can carry four oxygen molecules.
In the lung, Haemoglobin becomes oxyhemoglobin (reversible reaction)

Question 45

What is the partial pressure of oxygen?

Answer 45

The partial pressure of oxygen is a measure of oxygen concentration.
The greater the concentration of dissolved oxygen in cells, the higher the partial pressure.

Question 46

What is the partial pressure of carbon dioxide?

Answer 46

The partial pressure of carbon dioxide is a measure of the concentration of carbon dioxide in the cell.

Question 47

How is hemoglobin and the partial pressure of oxygen related?

Answer 47

Haemoglobin’s affinity for oxygen varies depending on the partial pressure of oxygen. Oxygen loads onto haemoglobin to form oxyhaemoglobin where there’s a higher partial pressure of oxygen. Oxyhaemoglobin unloads its oxygen where there is a lower partial pressure of oxygen.

Question 48

What are the passage and forms of hemoglobin in transport?

Answer 48

• Oxygen enters the blood from the alveoli in the lungs. Alveoli have a high pO2 so oxygen loads onto hemoglobin to form oxyhemoglobin.
• When cells respire, they use up oxygen- this lowers the pO2. Red blood cells deliver oxyhemoglobin to the tissues where it unloads its oxygen
• The hemoglobin then returns to the blood to pick up more oxygen.

Question 49

What does an oxygen dissociation curve show?

Answer 49

An oxygen dissociation curve shows how saturated the hemoglobin is with oxygen at any given partial pressure. When pO2 is high it has a high saturation of O2 and when pO2 is low it has a low saturation of oxygen.

Question 50

What does the shape of the oxygen dissociation curve show?

Answer 50

• The graph is s-shaped because when hemoglobin combines with the first O2 molecule, its shape alters in a way that makes it easier for other molecules to join too.
• But as the hemoglobin starts to become saturated, it gets harder for more oxygen molecules to join.
• As a result, the curve has a steep middle bit where it is really easy for oxygen molecules to join, and shallow bits at each end where it’s harder. When the curve is steep, a small change in pO2 causes a big change in the amount of oxygen carried by the hemoglobin.

Question 51

What are the differences between adult and fetal hemoglobin?

Answer 51

Fetal hemoglobin has a higher affinity for oxygen at the same partial pressure of oxygen.
- the fetus gets its blood from the mother across the placenta
- by the time the mother’s blood has reached the placenta its oxygen concentration is lower
- For the fetus to survive it must have a higher oxygen affinity to get enough from the blood
- If it was the same as adult hemoglobin the blood wouldn’t be saturated enough.

Question 52

How do Partial pressures of carbon dioxide affect oxygen unloading?

Answer 52

Hemoglobin gives up oxygen more readily at higher partial pressures of carbon dioxide. It is a good way of getting oxygen to cells during activity.
- CO2 from respiring tissues diffuses into red blood cells to react with water and form carbonic acid. (enzyme carbonic anhydrase)
- The carbonic acid dissociates to give hydrogen ions and hydrogencarbonate ions.
- The increase in hydrogen ions causes the hemoglobin to unload its oxygen so it can take up the ions. This forms haemoglobinic acid
- The hydrogen carbonate ions diffuse out of the red blood cells and are transported in the blood plasma. Chloride ions are diffused into the red load cells to combat the loss. This is called the chloride shift and it maintains the balance of charge between the red blood cell and the plasma.
- When the blood reaches the lungs the low pCO2 causes the recombination of the ions to CO2
- the CO2 is then breathed out via alveoli etc.