3.2 Transport in Animals

Question 1

Why do multicellular organisms require transport systems ?

Answer 1

Large size, small SA:V
High metabolic rates, demand for oxygen is high.

Question 2

Summarise the different types of circulatory systems.

Answer 2

Open : blood can diffuse out of vessels (insects)
Closed : blood confined to vessels (mammals/fish)
Single : blood passes through the heart once per circulation
Double : blood passes through the heart twice per circulation

Question 3

Relate the structure of the arteries to their function

Answer 3

Thick muscular walls to handle high pressure
Elastic tissue allows recoil
Narrow lumen to maintain pressure

Question 4

Relate the structure of the veins to their function.

Answer 4

Thin walls due to lower pressure
Valves to prevent back flow
Less muscular and elastic tissue as they don’t have to control blood flow

Question 5

Relate the structure of the capillaries to their function.

Answer 5

Walls only one cell thick for short diffusion pathway
Very narrow so can deliver O2 to muscles
Numerous and highly branched for a large SA

Question 6

Relate the structure of the arterioles and venules to their structure.

Answer 6

Branch off from arteries / veins in order to get blood to capillaries
Smaller than arteries and veins so that the change is blood pressure is gradual.

Question 7

What is tissue fluid ?

Answer 7

A watery substance of glucose, amino acids, oxygen and other nutrients
It supplies these nutrients to cells and also removes metabolic waste.

Question 8

What types of pressure influence formation of tissue fluid ?

Answer 8

Hydrostatic pressure - pressure from the heart. Higher at arterial end than venous end of capillary
Oncotic pressure - change in water potential of the capillaries as water moves out.

Question 9

How is tissue fluid formed ?

Answer 9

As blood is pumped through increasingly small vessels, hydrostatic pressure is greater than oncotic pressure
This makes fluid leave the capillaries
It then exchanges substances within the cells.

Question 10

How does tissue fluid differ from blood and lymph ?

Answer 10

Tissue fluid is formed from blood but does not contain RBCs or platelets (which are present in blood)
After tissue fluid has bathed cells it becomes lymph, meaning it has less nutrients and more waste products.

Question 11

Describe the blood flow through the heart.

Answer 11

-O
Vena cava -> right atrium -> tricuspid valve -> right ventricle -> semilunar valve -> pulmonary artery
+O
Pulmonary vein -> left atrium -> bicuspid valve -> left ventricle -> semilunar valve -> aorta.

Question 12

Describe what happens during cardiac diastole.

Answer 12

The heart is relaxed
Blood enters the atria, increasing the pressure and forcing open the atrioventricular valves
This allows blood to flow into the ventricles

Question 13

Describe what happens during atrial systole.

Answer 13

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

Question 14

Describe what happens during ventricular systole.

Answer 14

The ventricles contract
This increases pressure and closes the atrioventricular valves to prevent back flow, and also opens the semilunar valves
Blood now flows into the arteries.

Question 15

How do you calculate cardiac output ?

Answer 15

Cardiac output = heartrate x stroke volume

Question 16

What does myogenic mean ?

Answer 16

The hearts contraction is initiated from within the muscles themselves instead of nerve impulses.

Question 17

Explain how the heart contracts

Answer 17

•SAN creates wave of excitation which induces atrial systole
•Atrioventricular node delays impulse and sends it down the perkyn fibres in the septum
•When the impulse reaches the apex it induces ventricular systole

Question 18

The SAN initiates and spreads impulse across the atria, making them contract
The AVN receives, delays and then conveys the impulse down the bundle of His
Impulse travels into fibres which branch across of ventricles, causing contraction from the apex up.

Question 19

What is an electrocardiogram?

Answer 19

A graph showing the amount of electrical activity in the heart during the cardiac cycle.

Question 20

Describe the types of abnormal activity that may be seen on an ECG.

Answer 20

Tachycardia - fast resting heartbeat
Bradycardia - slow resting heartbeat
Fibrillation - irregular, fast heartbeat
Ectopic - early or extra heartbeats.

Question 21

Describe the role of haemoglobin.

Answer 21

Present in RBCs
Oxygen molecules bind to the haem groups and are carried around the body
They are released where they are needed in respiring tissues.

Question 22

How does partial pressure of oxygen affect O-Hb binding ?

Answer 22

As partial pressure of oxygen increases, the affinity of Hb for oxygen also increases : making O bind tightly to haemoglobin
When partial pressure is low, oxygen is released from Hb.

Question 23

What do oxyhaemoglobin dissociation curves show ?

Answer 23

Saturation of Hb with oxygen (%) plotted against partial pressure of O2 (kPa)
Curves further to the right show that Hb has a higher affinity for oxygen at higher partial pressures of oxygen.

Question 24

Describe the Bohr affect.

Answer 24

As partial pressure of carbon dioxide increases, the conditions become acidic
This causes Hb to change shape
This causers affinity of Hb for O2 to decrease, causing O2 to be released from Hb.

Question 25

Explain the role of carbonic anhydrase in the Bohr effect

Answer 25

Carbonic anhydrase is present in RBCs
It converts CO2 into carbonic acid, which dissociates to produce H+ ions
These ions combine with Hb to form haemoglobnic acid
This further encourages oxygen to dissociate from haemoglobin.

Question 26

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

Answer 26

These ions are produced alongside carbonic acid
70% of carbon dioxide is carried in this form
in the lungs bicarbonate ions are converted back into CO2, which we breathe out
It is carried like this as to not change the pH of the blood.

Question 27

Describe the chloride shift.

Answer 27

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

Question 28

How does foetal haemoglobin differ from adult haemoglobin?

Answer 28

The partial pressure of O2 is low by the time it reaches the foetus
Foetal Hb has a higher affinity for oxygen than adult, which allows both mother and child’s oxygen needs to be met.