Cardiac Muscle

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in the bath. Label the axes and give the graph a figure number and an appropriate title or legend. (3)

In the space below, paste the graph of active tension against calcium concentration (add more space as necessary with hard keyboard returns).

3) How can you account for this effect of the extracellular calcium concentration on contraction strength? (3)

4) What would you expect to happen to the contractions if the calcium concentration in the bathing solution was reduced completely to zero? Explain why. (2)

D. Effect of a Low Oxygen Environment

In the space below, paste a fully labeled graph of your experimental recording for this experiment, showing both the effect of the ‘de-oxygenated’ solution and the subsequent recovery in normal solution (add more space as necessary with hard keyboard returns). (5)

⦁ How did the active force at the end of the time in the ‘de-oxygenated’ solution compare with that produced by the muscle strip in the normal oxygen-containing solution? Present this in a quantitative way. (5)

⦁ Explain the effect of the ‘de-oxygenated’ solution on the active tension developed by the muscle. What aspect of the heart’s function does this illustrate? (5)

E. Effect of Adrenaline

In the space below, paste a fully labeled graph of your experimental recording showing the effect of adrenaline on the contractions of the isolated strip of cardiac muscle (add more space as necessary with hard keyboard returns). (5)

What was the percentage increase in active tension produced by adrenaline in your preparation? (Show your working out.) (5)

⦁ On what receptors does adrenaline act to produce this effect, and how is the subsequent increase in contraction strength brought about? (5)

⦁ What other action does adrenaline have in the intact heart? (5)

F. Effect of Nifedipine

In the space below, paste a fully labeled copy of your experimental recording showing the effect of nifedipine on the contractions of the isolated strip of cardiac muscle. (5)

⦁ Explain the effect of nifedipine on the contractions of the isolated strip of cardiac muscle.(5)

Conclusion

Provide a brief conclusion of what you consider these experiments showed about the control of the strength of cardiac muscle contraction, and how this relates to the function of the heart in the intact animal. (5)

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