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Calcium's Role in Myocardial Contraction

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Calcium's Role in Myocardial Contraction

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Questions and Answers

What was the significant discovery made by Ringer in 1883?

Protein-bound Ca2+ affects heart contraction.

Ca2+ is not necessary for heart function.

Ca2+ is essential for myocardial contraction. (correct)

Citrate-bound Ca2+ enhances heart contraction.

Which forms of calcium did McLean and Hastings find to have no effect on frog heart contraction?

Protein-bound Ca2+

Both B and C (correct)

Citrate-bound Ca2+

Ionized/free Ca2+

What is the mean concentration of blood-ionized Ca2+ in humans?

1.18 mmol/L (correct)

1.00 mmol/L

0.5 mmol/L

2.5 mmol/L

Why is it crucial to maintain ionized Ca2+ levels during surgery?

To maintain normal myocardial function. Signup and view all the answers

What condition may arise from decreased ionized Ca2+ concentrations in the blood?

Tetany Signup and view all the answers

Which of the following was a limitation of the first assay developed for ionized/free Ca2+?

Poor precision by today's standards. Signup and view all the answers

Study Notes

Calcium's Role in Myocardial Contraction

Ringer demonstrated in 1883 that calcium ions (Ca2+) are crucial for heart muscle contraction.
McLean and Hastings' research showed a direct relationship between free calcium concentration and the strength of frog heart contractions.
Bound calcium (protein-bound and citrate-bound) did not affect contraction strength.
This led to the development of the first assay for measuring free calcium using isolated frog hearts.
While the initial method lacked modern precision, it proved blood calcium concentrations are tightly regulated.
The average free calcium concentration in human blood is approximately 1.18 mmol/L.

Importance of Calcium Regulation

Maintaining normal free calcium levels is critical, especially during surgery and in critically ill patients, as low levels impair heart function.
Low free calcium levels in the blood can cause neuromuscular irritability, leading to muscle spasms (tetany).

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Description

This quiz explores the critical role of calcium ions in heart muscle contraction, highlighting key research findings. It reviews the historical context of calcium's impact on myocardiac function and the importance of maintaining normal calcium levels for heart health, particularly in surgical settings.