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 to prevent backflow
• less muscular and elastic tissue as don’t carry blood at as higher pressure

Question 4

Relate the structure of capillaries to their function?

Answer 4

• one cell thick walls mean short diffusion pathway
• very narrow so can permeate tissue effectively delivering O2 to tissues
• numerous and highly branched mean large SA

Question 5

Relate the structure of arterioles and venules to their function?

Answer 5

• branched of arteries and veins in order to feed blood into capillaries
• smaller than arteries and veins so that the pressure change is more gradual as blood passes through increasingly smaller vessels

Question 6

What is tissue fluid?

Answer 6

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

Question 7

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

Answer 7

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 8

How is tissue fluid formed?

Answer 8

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 9

How does tissue fluid differ from blood and lymph?

Answer 9

• 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 10

Describe what happens during cardiac diastole?

Answer 10

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

Question 11

Describe what happens during atrial systole?

Answer 11

atria contract pushing any remaining blood into the ventricles

Question 12

Describe what happens during ventricular systole?

Answer 12

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

Question 13

What does myogenic mean?

Answer 13

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

Question 14

Explain how the heart contracts?

Answer 14

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

Question 15

What is an ECG?

Answer 15

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

Question 16

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

Answer 16

tachycardia = fast heart beat >100bpm
bradycardia = slow heart beat <60bpm
fibrillation = irregular, fast heartbeat
ectopic = early or extra heartbeats

Question 17

Describe the role of haemoglobin?

Answer 17

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

Question 18

How does PP of O2 affect oxygen-haemoglobin binding?

Answer 18

• 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 19

What do oxygen-haemoglobin dissociation curves show?

Answer 19

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

Question 20

Describe the bohr effect?

Answer 20

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

Question 21

Describe the role of carbonic anhydrase in the bohr effect?

Answer 21

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

Question 22

Explain the role of bicarbonate ions in gas exchange?

Answer 22

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

Question 23

Describe the chloride shift?

Answer 23

• intake of chloride ions across a RBC membrane
• repolarises the cell after bicarbonate ions have diffused out

Question 24

How does foetal haemoglobin differ from adult haemoglobin?

Answer 24

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