Transport in animals

Question 1

Why do multicellular organisms require transport systems?

Answer 1

Large size (small SA : volume ratio)

O2 demand is high so needs a speacalised system to ensure a strong supply to respiring tissue

Question 2

Summarise the different types of circulatory systems?

Answer 2

open = blood can diffuse out of vessels
closed = blood confined to vessels

single = blood passes through the heart once per circuit of the body
double = blood passes through the heart twice per circuit of the body

Question 3

Relate the structure of arteries to their function?

Answer 3

Thick muscular walls = handle high pressure without tearing
Elastic tissue = recoils to prevent pressure surges
Narrow lumen = maintaining pressure

Question 4

Relate the structure of veins to their function?

Answer 4

Thin walls = due to lower pressure
Valves = prevent back flow
Less muscular/elastic tissue = don’t carry blood at as higher pressure

Question 5

Relate the structure of capillaries to their function?

Answer 5

1 cell thick walls = short diffusion pathway
Very narrow = can permeate tissue effectively delivering O2 to tissues
Numerous and highly branched = large SA

Question 6

Relate the structure of arterioles and venules to their function?

Answer 6

Branches of arteries and veins = feed blood into capillaries

Smaller than arteries and veins = pressure change is more gradual as blood passes through increasingly smaller vessels

Question 7

What is tissue fluid?

Answer 7

Watery substance containing glucose, amino acids, oxygen and other nutrients supplying these to cells and removing waste materials

Question 8

What types of pressure influence formation of tissue fluid and how?

Answer 8

Hydrostatic pressure = higher at arterial end of capillary than venous end

Oncotic pressure = changing water potential of the capillaries as water moves out induced by proteins in the plasma

Question 9

How is tissue fluid formed?

Answer 9

As blood’s pumped through increasingly small vessels hydrostatic pressure is greater than oncotic pressure so fluid moves out the capillaries

then exchanging substances with the cell

Question 10

How does tissue fluid differ from blood and lymph?

Answer 10

• tissue fluid formed from blood cells platelets and various other solutes present in blood
• after tissue fluid has bathed cells it becomes lymph therefore containing less O2 nutrients and more waste

Question 11

Describe what happens during cardiac diastole?

Answer 11

• heart is relaxed
• blood enters the atria increasing pressure opening AV valves allowing blood to flow into ventricles
• pressure in heart is lower than in arteries so semilunar valves remain closed

Question 12

Describe what happens during atrial systole?

Answer 12

Atria contract pushing any remaining blood into the ventricles

Question 13

Describe what happens during ventricular systole?

Answer 13

• ventricles contract
• pressure increases closing AV valves to prevent backflow
• semilunar valves open and blood flows into arteries

Question 14

What does myogenic mean?

Answer 14

The hearts contraction is initiated within the muscle itself rather than by nerve impulses

Question 15

Explain how the heart contracts?

Answer 15

1) SA node initiates and spread an impulse across the atria so they contract
2) AV node receives and delays impulse before conveying down bundle of his
3) impulse travels down purkinjee fibres branching across ventricles causing them to contract

Question 16

What is an ECG?

Answer 16

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

Question 17

Describe the abnormal activity that may be seen on an ECG?

Answer 17

Tachycardia = fast heart beat >100bpm
Bradycardia = slow heart beat <60bpm
Fibrillation = irregular, fast heartbeat
Ectopic = early or extra heartbeats

Question 18

Describe the role of haemoglobin?

Answer 18

• present in RBC
• O2 molecules bind to haem group and are transported round body
• O2 released where needed in respiring tissues

Question 19

How does PP of O2 affect oxygen-haemoglobin binding?

Answer 19

• as PP of O2 increases affinity of haemoglobin to oxygen also increases so O2 binds tightly to haemoglobin
• when PP is low oxygen is released from haemoglobin

Question 20

What do oxygen-haemoglobin dissociation curves show?

Answer 20

• saturation of haemoglobin with O2 (%) plotted against PP of O2 (kpa)
• curves further to left show haemoglobin has higher affinity to oxygen

Question 21

Describe the bohr effect?

Answer 21

• as PP of CO2 increases conditions become more acidic causing haemoglobin to change shape
• affinity of haemoglobin for oxygen therefore decreases so O2 is released from haemoglobin

Question 22

Describe the role of carbonic anhydrase in the bohr effect?

Answer 22

1) carbonic anhydrase is present in RBC
2) coverts CO2 to carbonic acid which dissociates to produce H+ ions
3) these combine with haemoglobin to form haemoglobinic acid
4) encourages O2 to dissociate from haemoglobin

Question 23

Explain the role of bicarbonate ions in gas exchange?

Answer 23

1) produced alongside carbonic acid
2) 70% of CO2 carried in this form
3) in the lungs bicarbonate ions are converted into CO2 to be expelled

Question 24

Describe the chloride shift?

Answer 24

Intake of chloride ions across a RBC membrane repolarising the cell after bicarbonate ions have diffused out

Question 25

How does foetal haemoglobin differ from adult haemoglobin?

Answer 25

- PP is low by time it reaches the foetus - therefore foetal haemoglobin has higher affinity for O2 than adult - allows both mother and childs O2 needs to be met