What is the Difference Between Autorhythmic and Contractile Cells

The main difference between autorhythmic and contractile cells is that autorhythmic cells serve as a pacemaker to initiate the cardiac cycle, whereas contractile cells conduct impulses responsible for the contraction of the heart muscle to pump blood. 

Autorhythmic and contractile cells are two cell types that occur in the heart. They make up the heart muscle and are responsible for pumping blood throughout the body through muscular contractions.  

Key Areas Covered

1. What are Autorhythmic Cells
– Definition, Structure, Function
2. What are Contractile Cells
– Definition, Structure, Function
3. Similarities Between Autorhythmic and Contractile Cells
– Outline of Common Features
4. Difference Between Autorhythmic and Contractile Cells
– Comparison of Key Differences

Key Terms 

Autorhythmic Cells, Contractile Cells

What are Autorhythmic Cells

Autorhythmic cells are the heart’s pacemaker, creating action potentials for cardiac muscle contraction. Cardiac muscle is capable of contracting very quickly in a wave-like pattern. The pacemaker cells within the cardiac muscle allow the muscle to contract in its rhythm in a process known as autorhythmicity. Sinoarterial (SA) node contains the highest concentration of autorhythmic cells. Also, autorhythmic cells occur in the atrioventricular (AV) node, His bundle, right bundle, left posterior bundle, Purkinje fibers, and Bachmann’s bundle.

Figure 1: Autorhythmic Cells

Furthermore, the pacemaker cells serve as a functional unit in stimulating cardiac muscle, and the pacemaker cells are referred to as syncytium. The pacemaker cells also receive neuron signals from the autonomic nervous system to increase or decrease the heart rate. The action potential of the cardiac muscle cells is relatively long. The cardiac muscles have a sustained depolarization known as a ‘plateau.’ The plateau contains channel proteins’ entry of calcium ions into the cardiac muscle cells. The sustained depolarization provides a longer contraction to the cardiac muscle.

What are Contractile Cells 

Contractile cells, cardiomyocytes, or cardiac muscle cells, are the cells that occur in the cardiac muscle. They are Y-shaped cells that are shorter and wider than skeletal muscles. Each cardiac muscle cell is mononucleated. The cardiac muscle cells comprise many mitochondria since it is high energy requiring muscle. The arrangement of actin and myosin striates the cardiac muscle cells. Thickly arranged myosin filaments form dark bands on the cardiac muscle cell, striating it. The light color bands occur due to the loosely arranged actin filaments.

Figure 2: Contractile Cells

Moreover, each cardiac muscle cell is in contact with another three or four cardiac muscle cells. Each cell’s overlapping region forms finger-like extensions called intercalated disks in the cell membrane. The structure of the intercalated disk forms gap junctions and desmosomes between the two cells, allowing the passage of electrochemical signals between the two cells. Also, autorhythmic cells connect neighboring cells through gap junctions. Further, contractile cells are responsible for pumping blood throughout the body of animals via highly coordinated, rhythmic muscular contractions.

Similarities Between Autorhythmic and Contractile Cells

• Autorhythmic and contractile cells are two cell types that occur in the heart.
• They are responsible for the heart muscle contraction that pumps blood throughout the body. 

Difference Between Autorhythmic and Contractile Cells

Definition

Autorhythmic cells refer to the specialized cardiac muscle cells that generate action potentials in the heart. In contrast, contractile cells refer to the myocardial cells that conduct impulses and are responsible for contractions that pump blood through the body. 

Significance

Autorhythmic cells serve as a pacemaker to initiate the cardiac cycle, while contractile cells conduct impulses responsible for heart muscle contraction to pump blood. 

Structure 

Autorhythmic cells are concentrated in the SA node, while contractile cells are Y-shaped heart muscle cells.

Function

Autorhythmic cells are responsible for generating action potentials required for heart muscle contraction, while contractile cells are responsible for pumping blood throughout the body. 

Conclusion

In brief, autorhythmic and contractile cells are the two cell types that occur in the heart. Autorhythmic cells serve as the heart’s pacemaker, producing action potentials to contract heart muscle. These cells are a type of specialized heart muscle cells, and they are concentrated in the SA node. In comparison, contractile cells are the cells in the heart muscle. They are Y-shaped and contract according to the action potentials generated by autorhythmic cells. The primary function of contractile cells is to pump blood throughout the body. Therefore, the main difference between autorhythmic and contractile cells is their function.

References:

1. Biga, L. M., Bronson, S., Dawson, S., Harwell, A., Hopkins, R., Kaufmann, J., LeMaster, M., Matern, P., Morrison-Graham, K., Oja, K., Quick, D., Runyeon, J., Oeru, O., & OpenStax. (2019, September 26). 2 cardiac muscle and electrical activity. Anatomy Physiology. 

Image Courtesy:

1. “Reizleitungssystem 1” By OpenStax CNX – Own work (CC-BY 2.5) via Commons Wikimedia
2. “2017abc Cardiac Muscle” By J. Heuser – Own Work (CC-BY 3.0) via Commons Wikimedia