Action Potentials and Contraction in Cardiac Muscle Cells

Leslie Samuel discusses action potentials and muscle contraction in cardiac cells. The episode covers the electrical connections in heart cells, the role of the SA and AV nodes, and the conduction velocity of signals. It explains how signals spread through the heart, causing the atria and ventricles to contract in sequence. The video also details the action potentials in cardiac muscle cells, highlighting the role of calcium in prolonging the action potential and facilitating muscle contraction.

What is the primary function of the SA node in the heart?

• To connect the atria and ventricles

• To act as the heart's pacemaker

• To slow down the heart rate

• To pump blood to the lungs

Why is there a delay at the AV node during heart contraction?

• To synchronize the contraction of the atria and ventricles

• To prevent blood from entering the lungs

• To increase the heart rate

• To allow the ventricles to fill with blood from the atria

What happens to the membrane potential of cardiac muscle cells during depolarization?

• It remains unchanged

• It depolarizes quickly

• It becomes more negative

• It repolarizes immediately

What is the role of calcium in cardiac muscle cells during an action potential?

• To initiate repolarization

• To increase conduction velocity

• To cause muscle contraction

• To decrease membrane potential

How does the action potential duration in cardiac muscle cells compare to that in neurons?

• It is shorter in cardiac muscle cells

• It varies depending on the heart rate

• It is longer in cardiac muscle cells

• It is the same in both

What phase is characterized by a slower repolarization in cardiac muscle cells?

• Repolarization phase

• Resting phase

• Depolarization phase

• Plateau phase

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

• They increase tension

• They relax

• They depolarize

• They contract