平滑肌与心肌
Most often, the term muscles mean the skeletal muscles for many of you, but there are two more types with a greater importance for survival of the animal. Smooth and cardiac muscles are the other two types. These two exhibit a great variation between each other with respect to their structure, function, and other properties.
Smooth Muscle
Smooth muscles are non-striated muscles found in the animal bodies and that are functional involuntarily. Smooth muscles are of two major types known as single unit, aka unitary, smooth muscles and multi-unit smooth muscles.
The single unit smooth muscles contract and relax together, as the nerve impulse excites only one muscle cell, and that is passed on to other cells through gap junctions. In other words, a unitary smooth muscle functions as a single unit of cytoplasm with numerous nuclei. On the other hand, the multi-unit smooth muscles have separate nerve supplies to pass signals into separate muscle cells to function independently.
光滑的肌肉几乎在体内到处都有，包括消化道，呼吸道，血管壁（静脉，动脉，动脉和主动脉），泌尿膀胱，子宫，尿道，眼睛，皮肤和许多其他地方。光滑的肌肉非常灵活，具有高弹性。当对平滑肌长度绘制张力值时，可以发现弹性特性很高。这些梭形肌肉在每个细胞中都有一个核，并且自主神经系统控制的收缩和松弛。这意味着无法按照您的意愿控制光滑的肌肉，但是那些可以按照应有的方式发挥作用。
Cardiac Muscle
Cardiac muscles are the muscles that form the heart. It is a type of striated muscles, and the altered segments of thick and thin protein fibres called myosin and actin respectively cause these striations. The main speciality of the cardiac muscles is that they are ever active with always undergoing through contractions and relaxations without coming to the fatigue state.
It is fascinating to know that the activities of cardiac muscles start since the foetal stages and last until the death. The main reasons for cardiac muscles stay unfatigued would be due to the extremely high supply of oxygen. The design of the circulatory system contributes to provide the blood with the highest concentration of oxygen for the cardiac muscles, so that there won’t be any demand for more to prevent fatigue.
The cardiac muscles are composed of cardiac muscle cells called cardiomyocytes. In each cardiomyocyte, there are either one or two nuclei, but sometimes there may be three or four nuclei in one cell. Cardiac muscles are rhythmically contracted and relaxed causing the rhythmic and inherent beats of the heart.
What is the difference between Smooth Muscle and Cardiac Muscle? • Smooth muscles are found in inner organs while cardiac muscles are found only in the heart. • Cardiac muscles are striated, but smooth muscles are non-striated. • Each cardiac muscle cell has one or more nuclei, but the smooth muscle cells are single nucleated. • Cardiac muscle cells are often branched, but smooth cells are non-branched. • Smooth muscle cells are fusiform-shaped, but cardiac muscle cells are long and cylindrical. |
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