The key difference between skeletal muscle and cardiac muscle is that skeletal muscle is under voluntary control while cardiac muscle is under involuntary control.
Muscle tissue is one of the four types of tissues present in the animal body. It has the ability to contract in order to facilitate movements of different parts of the body. Hence, muscle tissue is a contractile tissue. It originates from the mesoderm layer of embryonic germ cells. Based on the function, there are three main types of muscle tissues as skeletal muscle, cardiac muscle and smooth muscle. Among three different types, smooth muscle and cardiac muscle work involuntarily since their contraction occurs without conscious thought. In contrast, skeletal muscle works voluntarily as their contraction occurs with conscious thought. Moreover, cardiac muscle is present in the heart walls of vertebrates while skeletal muscle facilitates movements of our body by anchoring to the bones by tendons.
CONTENTS
1. Overview and Key Difference
2. What is Skeletal Muscle
3. What is Cardiac Muscle
4. Similarities Between Skeletal Muscle and Cardiac Muscle
5. Side by Side Comparison – Skeletal Muscle vs Cardiac Muscle in Tabular Form
6. Summary
What is Skeletal Muscle?
Skeletal muscle is a striated muscle anchored to bones by the bundles of collagen fibres called tendons. Skeletal muscle works completely under the voluntary control of the somatic nervous system. It facilitates locomotion, facial expressions, posture, and other voluntary movements of the body. Myocytes or muscle cells are the basic structural units of skeletal muscle. Muscle cells are organized into muscle fibres. Muscle fibres are long, cylindrical, multinucleated cells formed from the fusion of myoblasts.
Figure 01: Skeletal Muscle
Muscle fibres contain myofibrils composed of thick and thin myofilaments. Thin filaments are actin filaments while thick filaments are myosin filaments. Under the microscope view, these two filaments appear as distinctive banding patterns in skeletal muscle. In addition to these two, muscle fibres also contain troponin and tropomyosin, which are essential for muscle contraction. Actin and myosin are arranged in a repeating unit known as a sarcomere. It is the basic functional unit of muscle fibre and responsible for the striated appearance. Moreover, the interaction of actin and myosin is responsible for muscle contraction.
What is Cardiac Muscle?
Cardiac muscle is one of the three types of muscle tissue present in the walls of the heart, especially in the myocardium of the heart. Similar to skeletal muscle, cardiac muscle is also a striated muscle. But, it works involuntarily unlike the skeletal muscle. Cardiomyocytes or cardiac muscle cells are the cells that make the cardiac muscle. These cells have one, two or rarely three or four nuclei. Cardiac muscle cells depend on the blood supply to deliver oxygen and nutrients as well as to remove the waste products. Due to the coordinated contraction of heart muscle cells, blood circulation takes place in the circulatory system. For efficient functioning of the heart, cardiac muscles have a large number of mitochondria, numerous myoglobins, and good blood supply.
Figure 02: Cardiac Muscle
Cardiac muscles also exhibit cross striations by alternating thick and thin filaments. Under the electron microscope view, actin filaments appear as thin bands while myosin filaments appear as thick and darker bands. Cardiac muscle fibres are mostly branched. T-tubules in the cardiac muscle are larger, broader and run along the Z-Discs. Intercalated discs connect cardiac myocytes to an electrochemical syncytium and are responsible for force transmissions during muscle contraction. T-tubules play an important role in excitation-contraction-coupling (ECG).
What are the Similarities Between Skeletal Muscle and Cardiac Muscle?
- Skeletal muscle and cardiac muscle are two of the three types of muscles present in our body.
- Both are striated muscles.
- Therefore, they contain myofibrils and sarcomeres.
- Moreover, they are packed into highly regular arrangements of bundles.
- Both muscle types contain a large number of mitochondria.
What is the Difference Between Skeletal Muscle and Cardiac Muscle?
Skeletal muscle is the type of muscle attached to the skeleton by tendons while cardiac muscle is the muscle found in the walls of the heart. Thus, this is the key difference between skeletal muscle and cardiac muscle. Furthermore, skeletal muscle works under the voluntary control of the somatic nervous system while cardiac muscle works under involuntary control. Moreover, skeletal muscles are present in almost all part of the animal body while cardiac muscles are present only in the myocardium of the heart. This is another important difference between skeletal muscle and cardiac muscle.
The below infographic summarizes the difference between skeletal muscle and cardiac muscle.
Summary – Skeletal Muscle vs Cardiac Muscle
Skeletal muscle and cardiac muscle are two of the three types of muscle tissues. Skeletal muscle works voluntarily while cardiac muscle works involuntarily. This is the key difference between skeletal muscle and cardiac muscle. Furthermore, skeletal muscle fibres are cylindrical and long while cardiac muscle fibres have a branched structure. In addition, skeletal muscle fibres contain multiple nuclei while cardiac muscle fibres contain one or two nuclei.
Reference:
1. “ Muscle Tissues – Boundless Anatomy and Physiology.” Lumen, Available here.
2. ” Overview of Muscle Tissues” Anatomy and Physiology, OpenStax, 6 Mar. 2013, Available here.
Image Courtesy:
1. “Illu muscle structure” (Public Domain) via Commons Wikimedia
2. “Cardiac Muscle” By BruceBlaus – Own work (CC BY-SA 4.0) via Commons Wikimedia