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Biological Sciences
Stephen Reid

1 BGYC34 PhysioEx Lab 6 Cardiovascular Physiology Marking Scheme Part 1 Complete PhysioEx lab #6. Hand-in all of the pages associated with the lab. Note that there are 9 activities to be completed. You DO NOT need to hand in the histology review supplement. (5 marks) Activity 1: Recording Baseline Frog Heart Activity No questions Activity 2: Investigating the Refractory Period of Cardiac Muscle During which portion of the cardiac cycle was it possible to induce an extra systole? An extra systole can be triggered in the early/falling phase of ventricular diastole. (0.25) Attempt to tetanise the heart by clicking multiple stimulus. Electrical shocks will be delivered to the muscle at a rate of 20 stimuli/sec. What is the result? There is no tetanus. However, there were extra systoles. (0.25) Activity 3: Examining the Effect of Vagus Nerve Stimulation What is the effect of vagal stimulation on heart rate? Vagal stimulation slows the heart rate; possibly to zero. (0.25) Vagal escape is seen when the heart resumes beating. (0.25) Activity 4: Assessing the Effect of Temperature What change occurred with the cold (5ºC) Ringer’s solution? Heart rate decreased. (0.25) What change occurred with the warm (32ºC) Ringer’s solution? Heart rate increased. (0.25) What can you say about the effect of temperature on heart rate? Heart rate increases and decreases as temperature increases and decreases (i.e., a Q 10fect). 2 Activity 5: Assessing the Effect of Pilocarpine What happened when the heart was bathed in the pilocarpine solution? Pilocarpine caused a decrease in heart rate (pilocarpine is a muscarinic acetylcholine receptor agonist (i.e., it does the same as Ach). (0.75) Activity 6: Assessing the Effect of Atropine What was the effect of atropine on the heart? Atropine increased heart rate. (0.25) Atropine is a drug that blocks the effects of the neurotransmitter acetylcholine, liberated by the parasympathetic nervous system. Do your results accurately reflect this effect of atropine? Yes, atropine increased heart rate. (0.25) Are pilocarpine and atropine agonists or antagonists in their effects on heart rate? Pilocarpine and atropine are antagonist to each other (i.e., they do different things). Pilocarpine is an Ach agonist; atropine is an Ach antagonist. (0.25) Activity 7: Assessing the Effect of Epinephrine What happened when the heart was bathed in the epinephrine solution? Epinephrine increased heart rate. (0.25) Which division of the autonomic nervous system does its effect imitate? Epinephrine imitates the sympathetic nervous system. (0.5) Activity 8: Assessing the Effect of Digitalis What is the effect of digitalis on the heart? Digitalis reduces heart rate. (0.5) Activity 9: Assessing the Effect of Various Ions Effect of Ca (0.25) Does heart rate stabilise and remain stable? Calcium caused the heart rate to become irregular; speeding up at times, slowing down at others. Describe your observations of force and rhythm of the heart beat? Calcium increases the strength of contraction but it also causes an irregular rhythm. 3 Effect of Na (0.25) Does heart rate stabilise and remain stable? Sodium caused the
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