Transport in Animals

Question 1

What is a single circulatory system?

Answer 1

• A single circuit
• Fish have this
• Blood flows from (heart, gills, body, heart)

Question 2

What is a double circulatory system?

Answer 2

• Mammals have this
• Blood travels through heart twice for one complete circuit
• Pulmonary circulation carries blood to the lungs to pick up oxygen
• Systematic circulation carries oxygenated blood round the body
• Blood flows from (heart, body, heart, lungs, heart)

Question 3

What does a double circulatory system allow?

Answer 3

• Blood pressure to be raised after passing through lungs
• Blood flows more quickly to tissues
• Provides required nutrients for respiration
• Systematic circulation can have higher pressure than pulmonary

Question 4

What is an open circulatory system?

Answer 4

• Insects have this
• Blood (haemolymph) flows freely through the body cavity
• Oxygen diffuses into insects through spiracles (holes)
• Spiracles attached to tracheoles which are ventilated by contraction of the insects’s muscles

Question 5

What is a closed circulatory system?

Answer 5

• Mammals have this
• Blood closed within the vessels at all times
• Blood pumped by heart through the vessels
• Blood does not normally fill body cavities

Question 6

Arteries structure

Answer 6

• Thick walls, do not allow for diffusion of chemicals
• Strong walls made of elastic fibre
• Muscle swell and contract as blood surges through them every time heart beats
• Small lumen (keep blood pressure high and be able to withstand)
• Blood is at high pressure

Question 7

Arteries function

Answer 7

• Blood pumped into arteries by the ventricles of the heart
• Carry blood away from the heart
• Blood travels to other parts of the body (e.g. lungs and muscles)

Question 8

Veins function

Answer 8

• Bring blood back to heart as blood flows in one direction
• Do not pulse, helped by muscles to return to heart
• Muscles contract, squeeze blood back to heart
• Valves so blood is pumped in one way

Question 9

Veins structure

Answer 9

• Strong walls but thinner
• Valves : only allow blood to flow in one direction
• Large lumen, transport lots of blood + easy
• Thin outer wall

Question 10

Capillaries function

Answer 10

• Link between arteries and veins
• Diffusion into/out of blood happens here
  e.g. alveoli sacs lined with many capillaries

Question 11

Capillaries structure

Answer 11

• Outer wall only one cell thin : allow diffusion of substances into/out of blood of capillaries
• Steady blood flow
• Small lumen
• Very thin : has to be small enough to fit between cells

Question 12

Atrial systole

Answer 12

• Both atria contract together (systole)
• Small increase in pressure created by contraction helps to push blood from aorta into already partially full ventricles
• Stretches walls of ventricles
• AV valves then shut

Question 13

Ventricular systole

Answer 13

• Ventricles full of blood
• Begin to contract therefore pressure increases and volume decreases
• Contractions start at apex, push blood upwards towards arteries
• Semilunar valves forced open
• Blood pushes out of both ventricle and into the arteries
• Semilunar valves shut

Question 14

Diastole

Answer 14

• Both atria and ventricles relaxed
• Pressure decreases and internal volume increases
• Blood flows from heart into major veins
• Blood flows from atria, then through open atrioventricular valves and into ventricles
• “Filling phase”
• Atria and ventricles both have blood inside them

Question 15

Nervous control of the cardiac cycle

Answer 15

• Sinoatrial Node (SAN) sends signal across walls of both atria
• Signal causes atria to contract
• Signal reaches atrioventricular node (AVN)
• Slight delay before stimulating bundle of His (Purkyne fibres)
• Split into two branches, conduct wave of excitation from apex upwards
• Triggers contraction of ventricles