What is the Difference Between Contractile Cell and Pacemaker Cell

The key difference between contractile cell and pacemaker cell is that contractile cells are involved in muscular contractions in the process of pumping blood, while pacemaker cells are involved in creating rhythmic impulses that set the pace for the heart during the blood pumping process.

The heart is a major organ that enables the functionality of the circulation system. It is important since it pumps blood, which is the main circulatory media throughout the body, providing sufficient oxygen and other important metabolites. The conduction and contraction system of the heart consists of different cells that work in parallel for efficient blood pumping. Contractile cells and pacemaker cells are two such cell types involved in the main functions of the heart.

CONTENTS

1. Overview and Key Difference
2. What is a Contractile Cell  
3. What is a Pacemaker Cell
4. Similarities – Contractile Cell and Pacemaker Cell
5. Contractile Cell vs Pacemaker Cell in Tabular Form
6. Summary – Contractile Cell vs Pacemaker Cell

What is a Contractile Cell?

Contractile cell or cardiac myocyte is the type of cell that makes up the contractile tissue, enabling the heart to function as a pump. These cells are responsible for ensuring sufficient oxygenated blood and essential metabolites to the required tissues to meet the needs of the body. It is said that each contractile cell beats over three billion times in a normal human lifespan. A highly specialized subcellular mechanism is present within the contractile cells to synchronize the contraction and effective pumping.

Contractile cells have an organized sarcomere. These sarcomeres are striations where alternate patterns of A bands and light I bands attribute to the arrangement of the contractile cell. It comprises two main protein filaments: actin and myosin. These are the active substances that provide the functionality for contractile cells to perform cardiac muscular contractions. The sliding filament theory describes the contractility caused by the contractile cells.

What is a Pacemaker Cell?

Pacemaker cells are the cells responsible for creating rhythmic impulses in the heart that set the pace for blood pumping. These cells directly control the heart rate. Since they create rhythmic impulses, these cells make up the cardiac pacemaker, which is the natural pacemaker of the heart.

SA node is the natural pacemaker of humans. The rhythmic impulse is the sinus rhythm. During damage to the SA node, the electrical conduction system of the heart gets disrupted. This will result in cardiac arrhythmias due to the loss of functionality of pacemaker cells. Cardiac arrhythmias cause a blockage in the heart, where blood will not be pumped normally. This will cause failure in other organs and could lead to death. In such instances, the AV node acts as the pacemaker. If the AV node also fails, Purkinje fibers will manage the heart rate for a short period of time. During such incidents, the natural pacemaker is replaced by an artificial pacemaker, which is a device that mimics the same function of the pacemaker and pacemaker cells.

What are the Similarities Between Contractile Cell and Pacemaker Cell?

• Contractile and pacemaker cells are two types of eukaryotic cells.
• They are highly differentiated cells.
• They are present in the human heart.
• Moreover, both cell types are involved in the management of blood pumping.
• Contractile and pacemaker cells work based on electrical impulses.

What is the Difference Between Contractile Cell and Pacemaker Cell?

Contractile cells are involved in muscular contractions in the process of pumping blood, while pacemaker cells are involved in creating rhythmic impulses that set the pace for the heart during the blood pumping process. Thus, this is the key difference between contractile cell and pacemaker cell. Contractile cell is present in the contractile tissue, while pacemaker cell is present in the SA node and AV node. Moreover, contractile cell is characterized by the presence of sarcomeres, while pacemaker cell does not contain sarcomeres.

The below infographic presents the differences between contractile cell and pacemaker cell in tabular form for side by side comparison.

Summary – Contractile Cell vs Pacemaker Cell

The heart is a major organ that pumps blood throughout the body, providing sufficient oxygen and other important metabolites. Contractile cells and pacemaker cells are important in the overall functioning of the heart. Contractile cells are involved in muscular contractions in the process of pumping blood, while pacemaker cells are involved in creating rhythmic impulses that set the pace for the heart during the blood pumping process. So, this is the key difference between contractile cell and pacemaker cell.

Reference:

1. “Contractile Cells.” An Overview | ScienceDirect Topics.
2. “Cardiac Muscle and Electrical Activity.” Anatomy Physiology. Press Books.

Image Courtesy:

1. “Myocardiocyte” By OCAL (OpenClipart) – (CC0) via Commons Wikimedia
2. “Conduction system of the heart without the Heart-en” By Madhero88 (original files); Angelito7 (this SVG version) (CC BY-SA 3.0) via Commons Wikimedia