Transport in animals

Question 1

Why do multicellular organisms require transport systems?

Answer 1

They are large meaning they subsequently have high metabolic rates
Diffusion distance is too big for the cells further away from the surface so specialist transport systems are required

Question 2

Why dont single celled organisms require specialised transport systems?

Answer 2

Diffusion alone through the cell surface membrane is enough to absorb sufficient O2 and remove waste products such as CO2

Question 3

Summarise the different types of circulatory system.

Answer 3

• Open = blood can diffuse out of vessels e.g. insects
• Closed = Blood confined to vessels e.g. fish
  Two types of closed circulatory systems:
• Single = blood passes through heart once per circuit of the body
• Double = blood passes through the heart twice within one circuit of the body

Question 4

Relate the structure of arteries to their functions.

Answer 4

Thick, muscular walls: can handle high pressure without tearing
Elastic tissue: stretches and recoils to prevent pressure surges
Narrow lumen: to maintain pressure

Question 5

Relate the structure of veins to their function.

Answer 5

Thin walls due to lower pressure
Require valves to ensure blood doesnt flow backwards
Are less muscular and have less elastic tissue as they dont need to control blood flow

Question 6

Relate the structure of capillaries to their function.

Answer 6

Walls are one cell thick - short diffusion pathway
Very narrow so can permeate tissues to help aid red blood cells delivering oxygen
Numerous and highly branched - large surface area

Question 7

Relate the structure of arterioles and venules to their function

Answer 7

Branch off arteries and veins in order to feed blood into capillaries
Smaller than arteries and veins so that the change in pressure is gradual as blood passes through increasingly small blood vessels

Question 8

What is tissue fluid?

Answer 8

A watery substance containing glucose amino acids oxygen and other nutrients. It supplies these to the cells while also removing any waste materials.

Question 9

What types of pressure influence formation of tissue fluid?

Answer 9

Hydrostatic pressure = the pressure exerted by the blood onto the blood vessel walls, it is 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 10

How is tissue fluid formed?

Answer 10

As blood is pumped through increasingly small vessels, hydrostatic pressure is greater than oncotic pressure, so fluid moves out of the capillaries. It then exchanges substances with the cells.

Question 11

How does tissue fluid differ from blood and lymph?

Answer 11

Tissue fluid is formed from blood but does not contain red blood cells platelets and various other solutes which are usually present in blood.
After tissue fluid has bathed cells it becomes lymph and therefore this contains less oxygen and nutrients and more waste products

Question 12

Describe what happens during cardiac diastole.

Answer 12

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

Question 13

Describe what happens during atrial systole.

Answer 13

The atria contract to push any remaining blood into the ventricles

Question 14

Describe what happens during ventricular systole.

Answer 14

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

Question 15

How do you calculate cardiac output?

Answer 15

Heart rate x stroke volume

Question 16

What does myogenic mean?

Answer 16

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

Question 17

Explain how the heart contracts.

Answer 17

• The sinoatrial node initiates and spreads impulse across the atria so they contract simultaneously
• The atrioventricular node recieves the impulse but there is a slight delay of 0.1 seconds before it conveys the impulse down the bundle of His
• Impulse travels into the Purkyne fibres which branch across the ventricles so they contract simultaneously from the bottom up

Question 18

What is an electrocardiogram?

Answer 18

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

Question 19

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

Answer 19

Tachycardia - fast heartbeat (over 100bpm)
Bradycardia - slow heartbeat (under 60bpm)
Fibrillation - irregular, fast heartbeat
Ectopic - early or extra heartbeats

Question 20

Describe the role of haemoglobin.

Answer 20

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

Question 21

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

Answer 21

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

Question 22

What do oxyhaemoglobin dissociation curves show?

Answer 22

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 23

Describe the Bohr effect.

Answer 23

As partial pressure of carbon dioxide increases e.g. during exercise the conditions become acidic causing haemoglobin to change shape. The affinity for haemoglobin for oxygen therefore decreases so oxygen is released from haemoglobin

Question 24

Describe the chloride shift.

Answer 24

Carbon dioxide diffuses from aerobically respiring cells into tissue fluid, carbon dioxide then diffuses from the tissue fluid into the plasma. CO2 then diffuses from plasma into the red blood cell.
Within the red blood cell carbon dioxide reacts with water in a reversible reaction to produce carbonic acid in the presence of an enzyme catalyst (carbonic anhydrase) which then dissociates into a hydrogen carbonate ion (HCO3-) and a hydrogen ion (H+).
Finally hydrogen carbonate diffuses out of the red blood cell and the hydrogen ion reacts with haemoglobin to form haemoglobinic acid.
Because HCO3- diffuses out of the cell faster than hydrogen reacts with haemoglobin, chlorine ions have to move in to the cell to balance the charge.

Question 25

How does foetal haemoglobin differ from adult haemoglobin?

Answer 25

The partial pressure of oxygen is low by the time it reaches the foetus, therefore foetal haemoglobin has a higher affinity for oxygen than adult. This allows both mother and childs oxygen to be met