Module 3.2

Question 1

Why transport system is needed in multicellular animals

Answer 1

SA:V means diffusion distance is large, too slow and not sufficient
Size cells are further from the surface increasing diffusion distance
Animals are metabolically active as they are moving they have higher needs for oxygen and other substances which diffusion could not supply an efficient source of

Question 2

What is a single circulatory system

Answer 2

For each circulation of the body the blood only goes through the heart once

Question 3

What is a double circulatory system

Answer 3

For each circulation of the body the blood goes through the heart twice

Question 4

What is an open circulatory system

Answer 4

The blood/haemolymph is not contains within vessels, flows freely through the body cavity in direct contact with tissues

Question 5

What is a closed circulatory system

Answer 5

Blood is contained with vessels

Question 6

Structure of arteries

Answer 6

Narrow lumen
Endothelium
Elastic fibres
Thick smooth muscle layer
Collagen

Question 7

Arteries function

Answer 7

Carry high pressure blood away from the heart so the walls must be thick to withstand the pressure
Lumen is small to maintain high pressure
Elastic fibres help stretch and recoil

Question 8

Structure of arterioles

Answer 8

Narrow lumen
Endothelium
smooth muscle

Question 9

Function of arterioles

Answer 9

Distribute the blood from arteries to capillaries
Smooth muscle can constrict to reduce rate of blood flow to divert blood to more oxygen demanding tissues

Question 10

Structure of capillaries

Answer 10

1 cell thick wall
squamous epithelial cells
Leaky walls
Very narrow lumen (about same size as RBC

Question 11

Function of capillaries

Answer 11

Allow exchange of materials between the blood and tissue fluid
Narrow lumen squeezing RBCs helping transfer of oxygen and reducing diffusion distance
Leaky walls allow substances to leave the blood

Question 12

Structure of venules

Answer 12

Thin layer of muscle and elastic fibres
Thin outer layer of collagen

Question 13

Function of venules

Answer 13

Collect blood from the capillary bed and lead into veins

Question 14

Structure of veins

Answer 14

Wide lumen
valves to prevent backflow
Thin layers of collagen muscle and elastic fibres
Thin walls

Question 15

Function of veins

Answer 15

Carry blood back to the heart don’t need to stretch and recoil as blood is at low pressure
Thin walls means skeletal muscle can flatten the veins applying pressure to the blood and forcing it upwards

Question 16

Formation of tissue fluid

Answer 16

The beating of the heart generates hydrostatic pressure
As the capillary walls are leaky the fluid in the blood goes into the tissue (tissue fluid)

Question 17

How is tissue fluid different to plasma

Answer 17

Tissue fluid does not contain plasma proteins
does not contain most of the cells found in the blood

Question 18

What is lymph

Answer 18

When tissue fluid is directed into the lymph system
Contains more lymphocytes

Question 19

How oncotic pressure is established

Answer 19

Plasma proteins remain in the blood while tissue fluid is pushed through gaps in the capillary wall by hydrostatic pressure
This lowers the water potential of the blood below that of the tissue fluid
Water moves into the capillary by osmosis

Question 20

Structures of the heart

Answer 20

Cardiac muscle
Coronary arteries
Vena cava
Right atrium
Bicuspid (atrioventricular) valve
Right ventricle
septum
Semilunar valve
Pulmonary artery
Pulmonary vein
Left atria
Tricuspid (atrioventricular) valve
Left ventricle
Semilunar valve
Aorta

Question 21

Cardiac output equation

Answer 21

Heart rate x stroke volume

Question 22

Atrial systole

Answer 22

Blood enters the atria
Pressure rises above that of the ventricles forcing the atrioventricular valves open
The atria contracts forcing all of the blood to flow into the ventricles

Question 23

Ventricular systole

Answer 23

Ventricles contracts increasing pressure
Atrioventricular valves close to prevent backflow into the atria
Semilunar valves at the base of the arteries open as pressure in the ventricle is higher than the pressure in the arteries
Blood is pushed out of the ventricles into the arteries

Question 24

Diastole

Answer 24

Both atria and ventricles are relaxed
Semilunar valves are closed to prevent backflow into the ventricles
Atrioventricular valves are open

Question 25

Role of the Sino-atrial node

Answer 25

Initiates the cardiac cycle Sends a wave of excitation across the atria moving downwards so the atria contract downwards forcing blood into the ventricles Tissue at the top of the ventricle cannot conduct the wave so it goes to the sinoatrial node

Question 26

Role of the atrio-ventricular node

Answer 26

Delays the transmission so the atria can finish contracting an all blood enters the ventricles transmits the signal down purkyne tissue in the septum which does not produce a wave The wave of excitation spreads from the base of the ventricles upwards so that the blood is forced into the arteries

Question 27

What does myogenic mean

Answer 27

The heart muscle will contract on its own even without the body or signals but without the node the muscle fibres would all be contracting at different times causing fibrillation

Question 28

Role of haemoglobin - dissociation curve

Answer 28

At low partial pressures of oxygen (PPO2) oxygen does not readily associate with Hb as it is in the middle of the molecule and difficult to reach As PPO2 rises diffusion gradient increases, when 1 O2 enters the Hb and associates it produces a conformational change More O2 can then enter the Hb and associate

Question 29

Role of haemoglobin - CO2

Answer 29

CO2 enters RBCs and is broken down by carbonic anhydrase into carbonic acid This dissociates into H+ ions and hydrogen carbonate ions Hydrogen carbonate ions diffuse out of the RBC into the plasma, to maintain the charge chloride ions diffuse in (chloride shift) H+ ions would be a problem as they would make blood acidic Haemoglobin binds with the H+ ions forming haemoglobinic acid

Question 30

Why is haemoglobin a buffer

Answer 30

Maintains the pH of the RBC by taking up H+ ions

Question 31

What is the bohr shift

Answer 31

At higher CO2 concentration more oxygen will dissociate with haemoglobin at the same partial pressure as the haemoglobin is taking up H+ ions Helpful as respiring tissues get more oxygen

Question 32

Fetal haemoglobin

Answer 32

Has a higher affinity for oxygen. Placenta has a low partial pressure Maternal haemoglobin dissociates with oxygen Oxygen diffuses into fetal circulation Fetal haemoglobin is still able to associate with haemoglobin at the low partial pressure of the placenta because of its higher affinity

Question 33

Advantages of a double circulation

Answer 33

blood pressure through capillaries in exchange surface cannot be high - in double circulation it returns back to heart to have pressure raised Systematic circulation can carry blood at a higher pressure than the pulmonary circulation Rate at which oxygen and nutrients are delivered to respiring tissues is higher

Question 34

Closed circulation advantages

Answer 34

Blood flow is independent of movement Blood pressure is high and blood flow is fast More rapid delivery of oxygen and nutrients

Question 35

Return of tissue fluid to the blood

Answer 35

blood at the venous end of the capillary is at a lower hydrostatic pressure allowing tissue fluid to return to the blood Blood at the venous end has a lower water potential than the tissue fluid so water is pushed into the capillary by oncotic pressure

Question 36

Role of haemoglobin - transport

Answer 36

Oxygen diffuses into the blood and enters RBCs Binds with haemoglobin - oxyhaemoglobin Oxygen has been taken out of solution to maintain the concentration gradient

Question 37

Why is haemoglobin a buffer

Answer 37

As it takes H= ions out of solution it helps to maintain the pH of the blood as the H+ ions would make it acidic