Understanding Cardiac Muscle Contraction

Where does the signal for the heart to contract originate?

• SA node

• Bundle of His

• AV node

• Purkinje fibers

What happens when one cardiac muscle cell in the atria is stimulated?

• The signal stops

• The ventricles contract

• The entire atria contracts

• Only that cell contracts

Why is it important for the signal to slow down at the AV node?

• To ensure the atria and ventricles contract simultaneously

• To prevent the atria from contracting

• To allow the ventricles to contract first

• To allow the ventricles to fill with blood

What causes the depolarization of cardiac muscle cells?

• Chloride ions entering the cell

• Sodium ions entering the cell

• Calcium ions leaving the cell

• Potassium ions entering the cell

What is the plateau phase in cardiac muscle cells?

• A phase where the cell is at rest

• A rapid repolarization phase

• A phase where depolarization slows down

• A phase where the cell becomes hyperpolarized

What triggers muscle contraction in cardiac muscle cells?

• Release of sodium

• Release of potassium

• Release of calcium

• Release of chloride

What happens to the cardiac muscle cells when calcium is pumped back into the sarcoplasmic reticulum?

• They contract

• They relax

• They become hyperpolarized

• They depolarize

How long does the action potential in cardiac muscle cells last compared to neurons?

• Shorter than neurons

• Same as neurons

• Longer than neurons

• It varies

What is the role of the sarcoplasmic reticulum in cardiac muscle cells?

• To release chloride ions

• To store sodium ions

• To release calcium ions

• To store potassium ions

What is the effect of calcium release on cardiac muscle tension?

• Releases tension

• No effect on tension

• Increases tension

• Decreases tension