{"id":512,"date":"2021-01-17T23:13:45","date_gmt":"2021-01-17T23:13:45","guid":{"rendered":"https:\/\/pressbooks.publishdot.com\/anatomyphysiology\/chapter\/9-1-overview-of-muscle-tissues\/"},"modified":"2021-12-07T09:26:32","modified_gmt":"2021-12-07T09:26:32","slug":"9-1-overview-of-muscle-tissues","status":"publish","type":"chapter","link":"https:\/\/pressbooks.publishdot.com\/anatomyphysiology\/chapter\/9-1-overview-of-muscle-tissues\/","title":{"raw":"9.1 Overview of Muscle Tissues","rendered":"9.1 Overview of Muscle Tissues"},"content":{"raw":"
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Learning Objectives<\/strong><\/p>\n\n<\/header>\n

\n\nBy the end of this section, you will be able to:\n
    \n \t
  • Describe the different types of muscle<\/li>\n \t
  • Explain contractibility and extensibility<\/li>\n<\/ul>\n<\/div>\n<\/div>\nMuscle is one of the four primary tissue types of the body. The body contains three types of muscle tissue: skeletal muscle<\/strong>, cardiac muscle<\/strong>, and smooth muscle<\/strong> (Figure 9.1.1). All three muscle tissues have some properties in common; they all exhibit a quality called\u00a0excitability<\/strong>\u00a0as their plasma membranes can change their electrical states (from polarised to depolarised) and send an electrical wave called an action potential along the entire length of the membrane. While the nervous system can influence the excitability of cardiac and smooth muscle to some degree, skeletal muscle completely depends on signalling from the nervous system to work properly. On the other hand, both cardiac muscle and smooth muscle can respond to other stimuli, such as hormones and local stimuli.\n\n[caption id=\"attachment_511\" align=\"aligncenter\" width=\"445\"]\"Three Figure 9.1.1. The three types of muscle tissue.<\/strong> The body contains three types of muscle tissue: (a) skeletal muscle, (b) smooth muscle, and (c) cardiac muscle. From top, LM \u00d7 1600, LM \u00d7 1600, LM \u00d7 1600. (Micrographs provided by the Regents of University of Michigan Medical School \u00a9 2012).[\/caption]\n\nThe muscles all begin the actual process of contracting (shortening) when a protein called actin is pulled by a protein called myosin. This occurs in striated muscle (skeletal and cardiac) after specific binding sites on the actin have been exposed in response to the interaction between calcium ions (Ca2+) and proteins (troponin and tropomyosin) that \u201cshield\u201d the actin-binding sites. Ca2+\u00a0also is required for the contraction of smooth muscle, although its role is different: here Ca2+\u00a0activates enzymes, which in turn activate myosin heads. All muscles require adenosine triphosphate (ATP) to continue the process of contracting, and they all relax when the Ca2+\u00a0is removed and the actin-binding sites are re-shielded.\n\nA muscle can return to its original length when relaxed due to a quality of muscle tissue called\u00a0elasticity<\/strong>. It can recoil back to its original length due to elastic fibres. Muscle tissue also has the quality of\u00a0extensibility<\/strong>; it can stretch or extend.\u00a0Contractility<\/strong>\u00a0allows muscle tissue to pull on its attachment points and shorten with force.\n\nDifferences among the three muscle types include the microscopic organisation of their contractile proteins\u2014actin and myosin. The actin and myosin proteins are arranged very regularly in the cytoplasm of individual muscle cells (referred to as fibres) in both skeletal muscle and cardiac muscle, which creates a pattern, or stripes, called striations. The striations are visible with a light microscope under high magnification (see\u00a0Figure 9.1.1).\u00a0Skeletal muscle fibres <\/strong>are multinucleated structures that compose the skeletal muscle.\u00a0Cardiac muscle\u00a0fibres each have one to two nuclei and are physically and electrically connected to each other so that the entire heart contracts as one unit (called a syncytium).\n\nBecause the actin and myosin are not arranged in such regular fashion in\u00a0smooth muscle<\/strong>, the cytoplasm of a smooth muscle fibre (which has only a single nucleus) has a uniform, nonstriated appearance (resulting in the name smooth muscle). However, the less organised appearance of smooth muscle should not be interpreted as less efficient. Smooth muscle in the walls of arteries is a critical component that regulates blood pressure necessary to push blood through the circulatory system; and smooth muscle in the skin, visceral organs, and internal passageways is essential for moving all materials through the body.\n
    \n

    Section Review<\/strong><\/p>\n\n<\/header>\n

    \n\nMuscle is the tissue in animals that allows for active movement of the body or materials within the body. There are three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Most of the body\u2019s skeletal muscle produces movement by acting on the skeleton. Cardiac muscle is found in the wall of the heart and pumps blood through the circulatory system.\n\nSmooth muscle is found in the skin, where it is associated with hair follicles; it also is found in the walls of internal organs, blood vessels and internal passageways, where it assists in moving materials.\n\n<\/div>\n<\/div>\n
    \n

    Review Questions<\/strong><\/p>\n\n<\/header>\n

    \n\n[h5p id=\"243\"]\n\n<\/div>\n<\/div>\n
    \n

    Critical Thinking Question<\/strong><\/p>\n\n<\/header>\n

    \n\n[h5p id=\"244\"]\n\n<\/div>\n<\/div>\nClick the drop down below to review the terms learned from this chapter.\n\n[h5p id=\"245\"]","rendered":"
    \n
    \n

    Learning Objectives<\/strong><\/p>\n<\/header>\n

    \n

    By the end of this section, you will be able to:<\/p>\n

      \n
    • Describe the different types of muscle<\/li>\n
    • Explain contractibility and extensibility<\/li>\n<\/ul>\n<\/div>\n<\/div>\n

      Muscle is one of the four primary tissue types of the body. The body contains three types of muscle tissue: skeletal muscle<\/strong>, cardiac muscle<\/strong>, and smooth muscle<\/strong> (Figure 9.1.1). All three muscle tissues have some properties in common; they all exhibit a quality called\u00a0excitability<\/strong>\u00a0as their plasma membranes can change their electrical states (from polarised to depolarised) and send an electrical wave called an action potential along the entire length of the membrane. While the nervous system can influence the excitability of cardiac and smooth muscle to some degree, skeletal muscle completely depends on signalling from the nervous system to work properly. On the other hand, both cardiac muscle and smooth muscle can respond to other stimuli, such as hormones and local stimuli.<\/p>\n

      \"Three
      Figure 9.1.1. The three types of muscle tissue.<\/strong> The body contains three types of muscle tissue: (a) skeletal muscle, (b) smooth muscle, and (c) cardiac muscle. From top, LM \u00d7 1600, LM \u00d7 1600, LM \u00d7 1600. (Micrographs provided by the Regents of University of Michigan Medical School \u00a9 2012).<\/figcaption><\/figure>\n

      The muscles all begin the actual process of contracting (shortening) when a protein called actin is pulled by a protein called myosin. This occurs in striated muscle (skeletal and cardiac) after specific binding sites on the actin have been exposed in response to the interaction between calcium ions (Ca2+) and proteins (troponin and tropomyosin) that \u201cshield\u201d the actin-binding sites. Ca2+\u00a0also is required for the contraction of smooth muscle, although its role is different: here Ca2+\u00a0activates enzymes, which in turn activate myosin heads. All muscles require adenosine triphosphate (ATP) to continue the process of contracting, and they all relax when the Ca2+\u00a0is removed and the actin-binding sites are re-shielded.<\/p>\n

      A muscle can return to its original length when relaxed due to a quality of muscle tissue called\u00a0elasticity<\/strong>. It can recoil back to its original length due to elastic fibres. Muscle tissue also has the quality of\u00a0extensibility<\/strong>; it can stretch or extend.\u00a0Contractility<\/strong>\u00a0allows muscle tissue to pull on its attachment points and shorten with force.<\/p>\n

      Differences among the three muscle types include the microscopic organisation of their contractile proteins\u2014actin and myosin. The actin and myosin proteins are arranged very regularly in the cytoplasm of individual muscle cells (referred to as fibres) in both skeletal muscle and cardiac muscle, which creates a pattern, or stripes, called striations. The striations are visible with a light microscope under high magnification (see\u00a0Figure 9.1.1).\u00a0Skeletal muscle fibres <\/strong>are multinucleated structures that compose the skeletal muscle.\u00a0Cardiac muscle\u00a0fibres each have one to two nuclei and are physically and electrically connected to each other so that the entire heart contracts as one unit (called a syncytium).<\/p>\n

      Because the actin and myosin are not arranged in such regular fashion in\u00a0smooth muscle<\/strong>, the cytoplasm of a smooth muscle fibre (which has only a single nucleus) has a uniform, nonstriated appearance (resulting in the name smooth muscle). However, the less organised appearance of smooth muscle should not be interpreted as less efficient. Smooth muscle in the walls of arteries is a critical component that regulates blood pressure necessary to push blood through the circulatory system; and smooth muscle in the skin, visceral organs, and internal passageways is essential for moving all materials through the body.<\/p>\n

      \n
      \n

      Section Review<\/strong><\/p>\n<\/header>\n

      \n

      Muscle is the tissue in animals that allows for active movement of the body or materials within the body. There are three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Most of the body\u2019s skeletal muscle produces movement by acting on the skeleton. Cardiac muscle is found in the wall of the heart and pumps blood through the circulatory system.<\/p>\n

      Smooth muscle is found in the skin, where it is associated with hair follicles; it also is found in the walls of internal organs, blood vessels and internal passageways, where it assists in moving materials.<\/p>\n<\/div>\n<\/div>\n

      \n
      \n

      Review Questions<\/strong><\/p>\n<\/header>\n

      \n
      \n