full answers to questions 4, 5, 6 and 7 on page 64.

1. a) look these up 4 marks
   b) they are valves - think about how they control blood flow
   c)
   i) oxygenated so the left, into the heart so the atrium
   ii) from the body so the right, into the heart so an atrium

2. a)
   i) look for one with evidence of haemoglobin in it - why is that useful?
   ii) look for one with a big nucleus - why is that useful?
   iii) look for one with a mobile cell membrane - why is that useful?

b)
there are lots to choose from. Find a function for any of these

platelet
hormone
glucose

1. a) look for a high heart rate
   b) look for something sudden
   c) look for a low steady heart rate
   d) look for a gradual increase

2. a
   i) state the rate (roughly 70bpm) - say why
   ii) state what happens to the rate - say why
   iii) state what happens to the rate - say why
   b
   would a fit person would recover faster or slower than an unfit person?