The key difference between contractile myocardium and autorhythmic myocardium is that contractile myocardium is a type of cardiac muscle that conducts impulses responsible for contraction in order to pump blood throughout the body, while autorhythmic myocardium is a type of cardiac muscle that serves as a pacemaker to initiate the cardiac cycle and provides a conduction system to coordinate the contraction of muscle cells throughout the heart.
There are two types of cardiac muscles cells: contractile myocardium and autorhythmic myocardium. Contractile myocardium constitutes the bulk of cells (99%) in the atria and ventricles. These cells are carried out the function of contraction. On the other hand, autorhythmic myocardium constitutes 1% of the heart cells, and they form the conduction system of the heart.
CONTENTS
1. Overview and Key Difference
2. What is Contractile Myocardium
3. What is Autorhythmic Myocardium
4. Similarities – Contractile Myocardium and Autorhythmic Myocardium
5. Contractile Myocardium vs Autorhythmic Myocardium in Tabular Form
6. Summary – Contractile Myocardium vs Autorhythmic Myocardium
What is Contractile Myocardium?
Contractile myocardium is a major type of cardiac muscle that conducts impulses responsible for contraction in order to pump blood throughout the body. Contractile myocardium constitutes the bulk of cells (99%) in the atria and ventricles. Myocardial contractility represents the innate ability of the heart muscle (contractile myocardium) to contract. The ability to produce changes in force during contraction normally results in an incremental degree of binding between different types of tissue, such as filaments of myosin (thick) and actin (thin) tissue.
Moreover, the degree of binding depends on the concentration of calcium ions in the contractile myocardium of contractile cells. Furthermore, within an in vivo intact heart, the action response of the sympathetic nervous system is driven by precisely timed releases of catecholamine. This is a process that determines the calcium ions in the cytosol of contractile cardiac muscle cells. Therefore, the factors causing an increase in contractility in the heart work by causing an increase in intracellular calcium ions during contraction. Under one existing model, the five factors of contractile myocardium performance are considered to be heart rate, conduction velocity, preload, afterload, contractility.
What is Autorhythmic Myocardium?
Autorhythmic myocardium is a type of cardiac muscle that serves as a pacemaker to initiate the cardiac cycle and provides a conduction system to coordinate the contraction of muscle cells throughout the heart. Autorhythmic myocardium constitutes 1% of the heart cells, and they form the conduction system of the heart. Moreover, except for Purkinje cells, they are generally much smaller than contractile cells and have only a few of the myofibrils or filaments needed for contraction.
Figure 01: Cardiac Conduction
Their function is similar to neurons, although they are specialized muscle cells. Action potentials or electrical impulses in the heart originate in specialized cardiac muscle cells called autorhythmic cells. These cells are self excitable and are able to generate an action potential without external stimulation by nerve cells. Autorhythmic cells are concentrated in the areas of the sinoatrial node, atrioventricular node, atrioventricular bundle, and Purkinje fibers. Autorhythmic cells initiate and propagate the action potential that travels throughout the heart and triggers the contractions that propel the blood.
What are the Similarities Between Contractile Myocardium and Autorhythmic Myocardium?
- Contractile myocardium and autorhythmic myocardium are two types of cardiac muscles cells.
- Both are collectively responsible for pumping blood through the body.
- Their function is extremely important for the survival of animals, including humans.
- Their functional errors can cause diseases such as cardiomyopathy and heart attack.
What is the Difference Between Contractile Myocardium and Autorhythmic Myocardium?
Contractile myocardium is a type of cardiac muscle that conducts impulses and is responsible for contraction in order to pump blood throughout the body, while autorhythmic myocardium is a type of cardiac muscle that serves as a pacemaker to initiate the cardiac cycle and provides a conduction system to coordinate the contraction of muscle cells throughout the heart. Thus, this is the key difference between contractile myocardium and autorhythmic myocardium. Furthermore, contractile myocardium constitutes the bulk of cells (99%) in the heart cells, while autorhythmic myocardium constitutes 1% of the heart cells.
The below infographic presents the differences between contractile myocardium and autorhythmic myocardium in tabular form for side by side comparison.
Summary – Contractile Myocardium vs Autorhythmic Myocardium
Contractile myocardium and autorhythmic myocardium are two types of cardiac muscles that are collectively responsible for pumping blood through the body. Contractile myocardium conducts impulses that are responsible for contraction in order to pump blood throughout the body. Autorhythmic myocardium is a type of cardiac muscle that serves as a pacemaker to initiate the cardiac cycle and provides a conduction system to coordinate the contraction of muscle cells throughout the heart. So, this is the key difference between contractile myocardium and autorhythmic myocardium.
Reference:
1. “17.3: Cardiac Muscle and Electrical Activity.” Medicine LibreTexts, Libretexts.
2. “Cardiac-conduction |Anatomy and Physiology.” CliffsNotes.
Image Courtesy:
1. “2019 Cardiac Conductionn” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia