Tasks 8-9

8. Refractory Period

  1. define the term refractory period.
  2. explain the observed effects of stimulating the heart electrically during ventricular contraction and during ventricular relaxation.
  3. estimate the duration of the refractory period in ms. How does this compare with the refractory period of skeletal muscle?
  4. explain the terms 'extra systole' and 'compensatory pause'.

8. Stannius Ligatures
  1. measure the heart rate after tying Stannius ligature I and Stannius ligature II.
  2. after application of Stannius ligature I does the rate of atrial contraction change?
  3. after application of Stannius ligature II does the ventricle become quiescent (stop contracting) or does it beat spontaneously?
  4. do the different chambers of the heart have their own inherent rhythms? If so which chamber (sinus venosus, atria, ventricle) has the fastest inherent rhythm?