Circulation

Question 1

Why do large multicellular organisms need transport systems?

Answer 1

They have a small surface area to volume ratio and a high metabolic rate. Therefore the rate of diffusion alone would not be fast enough to transport substances to where they are needed.

Question 2

Give 4 examples of substances transported within organisms

Answer 2

-Oxygen is transported in for respiration
-CO2 is transported out from respiration
-Dissolved food molecules from digestion
-Waste products such as urea in humans

Question 3

What is mass transport?

Answer 3

The bulk transport of substances to all parts of an organism using mass flow

Question 4

Give features of a mass transport system.

Answer 4

-Vessles
-Transport medium
-A mechanism for maintaining flow

Question 5

What is the difference in function between veins, arteries and capillaries?

Answer 5

Arteries carry blood away from the heart. Veins carry blood towards the heart.
Capillaries flow close to tissues for exchange

Question 6

Describe the structure of arteries

Answer 6

They have thick walls made of muscle and elastic tissue and a small lumen to transport blood under high pressure

Question 7

Describe the structure of capillaries

Answer 7

They have thin walls (about one cell thich) to allow for the easy exchange of substances at the tissues

Question 8

Describe the structure of veins

Answer 8

Veins have less muscle and elastic tissue than arteries and they have a larger lumen because the blood is at lower pressure. They also have valves to prevent backflow.

Question 9

Main artery which takes oxygenated blood out of the heart for transport around the body

Answer 9

Aorta

Question 10

Main vain which carries deoxygenated blood from the body into the heart

Answer 10

Vena cava

Question 11

Main artery which supplies the heart tissue with oxygenated blood

Answer 11

Coronary artery

Question 12

Artery which transports deoxygenated blood from the heart to the lungs

Answer 12

Pulmonary artery

Question 13

Vein which transports oxygenated blood from the lungs back to the heart

Answer 13

Pulmonary vein

Question 14

What is the cardiac cycle?

Answer 14

The sequence of events involved in one cycle of contraction and relaxation of the heart. It involves 3 stages: atrial systole, ventricular systole and diastole.

Question 15

What happens during cardiac diastole?

Answer 15

The heart is relaxed. Blood enters the atria, increasing pressure and pushing the atrioventricular valves open. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so semilunar valves remain closed.

Question 16

What happens during atrial systole?

Answer 16

The atria contract, pushing any remaining blood into the ventricles.

Question 17

What happens during ventricular systole?

Answer 17

The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow and opening the semilunar valves. Blood flows into the arteries.

Question 18

Which side of the heart receives blood from the body and pumps it to the lungs?

Answer 18

The right side of the heart.

Question 19

Which side of the heart receives blood from the lungs and pumps it to the body?

Answer 19

The left side of the heart.

Question 20

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

Answer 20

The left ventricle has to pump blood around the whole body so the blood needs to be at a higher pressure.

Question 21

Describe the blood flow through the right side of the heart.

Answer 21

-Deoxygenated blood flows into the right atrium from the vena cava
-This blood passes through the right AV valve into the right ventricle
-The blood is then pumped out of the heart to the lungs through the right SL valve into the pulmonary artery.

Question 22

Describe the blood flow through the left side of the heart.

Answer 22

-Blood enters into the left atrium from the pulmonary vein
-The blood is pumped through the left AV valve into the left ventricle
-The blood is then pumped out through the left SL valve into the aorta

Question 23

What is the function of the valves in the heart?

Answer 23

They prevent backflow of the blood so it only flows i one direction.

Question 24

What is the name of the wall that separates the right and left sides of the heart?

Answer 24

The septum.

Question 25

What type of muscle is the heart made of?

Answer 25

Cardiac muscle.

Question 26

Relate the structure of the chambers to their functions.

Answer 26

Atria: thin-walled and elastic so they can stretch when filled with blood.
Ventricles: Thick muscular walls pump blood under high pressure. The left ventricle is thicker than the right because to has to pump blood all the way around the body.

Question 27

Relate the structure of arteries to their function

Answer 27

Thick, muscular walls to handle high pressure without tearing.l Elastic tissue allows recoil. Narrow lumen to maintain pressure.

Question 28

Why are two pumps (left and right) needed instead of one?

Answer 28

To maintain blood pressure around the whole body. When blood passes through the lungs’ capillaries, pressure drops sharply and does not flow strongly enough to continue around the whole body. Therefore it is returned to the heart to increase pressure.

Question 29

Describe the structure of erythrocytes (red blood cells) and their function.

Answer 29

Biconcave shape, no nucleus, contain lots of haemoglobin. Their function is to carry oxygen.

Question 30

Describe the structure of haemoglobin

Answer 30

A globular conjugated protein. It has a quaternary structure consisting of 2 alpha chains and 2 beta chains. They each contain a haem prosthetic group which has iron ions that can bind to oxygen.

Question 31

Describe the role of haemoglobin

Answer 31

Present in red blood cells. Oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues.

Question 32

How does the partial pressure of oxygen affect oxygen-haemoglobin binding?

Answer 32

As partial pressure increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressure is low, the oxygen is released from haemoglobin.

Question 33

State 3 ways in which carbon dioxide (CO2) is transported in the blood

Answer 33

-Combined with haemoglobin as carbaminohaemoglobin
-Dissolved in plasma
-As hydrogencarbonate ions (HCO3-) from the dissociation of carbonic acid

Question 34

Explain the Bohr effect

Answer 34

As the partial pressure of CO2 increases, the conditions become acidic and cause the haemoglobin to change shape. The affinity of haemoglobin for oxygen therefore decreases and oxygen is released from haemoglobin.

Question 35

What do haemoglobin dissociation curves show?

Answer 35

Saturation of haemoglobin with oxygen (in %), plotted against partial pressure of oxygen (in kPa). Curves further to the left show the haemoglobin has a higher affinity for oxygen.

Question 36

Explain the role of carbonic anhydrase in the Bohr effect.

Answer 36

-Carbonic anhydrase is present in red blood cells
-Converts carbon dioxide to carbonic acid, which dissociates to produce H+ ions.
-These combine with haemoglobin to form haemoglobinic acid.
-Encourages oxygen to dissociate from haemoglobin.

Question 37

Explain the role of bicarbonate ions (HCO3-) in gas exchange

Answer 37

Produced alongside carbonic acid. 70% of the carbon dioxide is carried in this form. In the lungs, bicarbonate ions are converted back into carbon dioxide which we breathe out.

Question 38

Describe the chloride shift

Answer 38

The intake of chloride ions across a red blood cell membrane. This repolarises the cell after bicarbonate ions have diffused out.