Which of the following descriptions of cardiac pacemaker cells is incorrect?

• A. They have the ability to generate action potentials spontaneously.
• B. They help regulate the heart rate by controlling the timing of contractions.
• C. They require external neural input to initiate each heartbeat.
• D. They are primarily located in the sinoatrial node.

Answer: (C)

Verified step by step guidance

1. Understand the role of cardiac pacemaker cells: These cells are specialized cells in the heart that have the ability to generate action potentials spontaneously, which means they can initiate electrical impulses without external stimuli.
2. Identify the primary location of pacemaker cells: The sinoatrial (SA) node, located in the right atrium of the heart, is the primary pacemaker of the heart. It sets the pace for the heart rate by generating regular electrical impulses.
3. Recognize the function of pacemaker cells in heart rate regulation: Pacemaker cells help regulate the heart rate by controlling the timing of heart contractions, ensuring that the heart beats in a coordinated and rhythmic manner.
4. Evaluate the statement about external neural input: Pacemaker cells do not require external neural input to initiate each heartbeat. They are capable of automaticity, meaning they can generate impulses independently.
5. Determine the incorrect description: Based on the understanding that pacemaker cells can spontaneously generate action potentials and do not need external neural input, the statement 'They require external neural input to initiate each heartbeat' is incorrect.