Question

in cardiac muscle

calcium ions are not released from the sarcoplasmic reticulum.
calcium ions do not bind to troponin molecules.
calcium ions play not role in the process of contraction.
a portion of the calcium ion required for contraction comes from outside the cell.
calcium ions play an important role in repolarizing the membrane after the depolarization phase.

question 14
abnormally slow depolarization of the ventricles would mostly change the shape of the _________ in and ekg tracing.

p wave
t wave
qrs complex
p-r interval
r-t interval

Explanation:

Analyze cardiac muscle calcium dynamics

In cardiac muscle, contraction relies on calcium-induced calcium release (CICR). When an action potential depolarizes the sarcolemma, extracellular calcium enters the cell through L-type calcium channels. This influx of extracellular calcium triggers the release of a much larger amount of calcium from the sarcoplasmic reticulum via ryanodine receptors. Therefore, a portion of the calcium required for contraction must come from outside the cell. This makes the fourth option correct, while the others are incorrect because calcium is released from the sarcoplasmic reticulum, binds to troponin, plays a vital role in contraction, and is not the primary ion responsible for repolarization.

Analyze ventricular depolarization on an EKG

An electrocardiogram (EKG) records the electrical activity of the heart through specific waveforms:

• The P wave represents atrial depolarization.
• The QRS complex represents ventricular depolarization.
• The T wave represents ventricular repolarization.

An abnormally slow depolarization of the ventricles would directly alter the duration and shape of the QRS complex, as this complex represents the spread of electrical activation through the ventricular myocardium.

Answer:

Question 1

• calcium ions are not released from the sarcoplasmic reticulum.
• calcium ions do not bind to troponin molecules.
• calcium ions play not role in the process of contraction.
• a portion of the calcium ion required for contraction comes from outside the cell. (Correct answer)
• calcium ions play an important role in repolarizing the membrane after the depolarization phase.

Question 2

• P wave
• T wave
• QRS complex (Correct answer)
• P-R interval
• R-T interval