9a.Muscle+short - MUSCLE (1 Skeletal:Hasstriations,,...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
MUSCLE The three types of muscle tissue are:   (1) Skeletal :   Has striations, controlled voluntarily, contracts rapidly but tires  easily, is responsible for overall body movement, & adaptable exerting forces  over a range from a fraction of an ounce to over 70 pounds. Has three basic  types of fibers discussed later. (2) Cardiac:   Occurs in the heart, striated like skeletal muscle,  not  voluntary, one  nucleus, contracts at a fairly steady rate set by the heart’s pacemaker, neural  control via vagus & accelerator nerves allows the heart to respond to bodily  needs.  Intercalated discs allow function as a syncytium : two syncytia -atrial and ventricular. Sinoatrial node is rhythmic because membrane permeability to sodium changes (decreases briefly) after contraction, and then increases to lower threshold or increase sensitivity . (3) Smooth:   Found in walls of hollow visceral organs, ex. stomach, urinary  bladder, blood vessels, excretory ducts, reproductive ducts & respiratory  passages, not  striated and is involuntary , forces food and other substances  through internal body channels. Actin attaches to dense bodies, not Z-lines.  Much more actin than myosin. Varicosities on postganglionic fibers.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
TYPES OF MUSCLE              (1)  Skeletal-voluntary, syncytium (multinucleate approx. 100 nuclei/cell),  striated fibers. Amitotic. There are three basic types of skeletal muscle fibers  recognized, but also some which might be called hybrids of the three. All muscles,  even in other vertebrates, have various percentages of these fibers average about 50%  slow and 50% fast fibers. Most people have 20 to 40% Type I fibers, but vary in  number to Type II fibers. A.  Type I-High oxidative (red)  slow fibers  – aerobic for endurance,  and have low tension; more mitochondria, myoglobin, capillaries and enzymes of  aerobic metabolism (red fibers). ATPases are slow. Less glycogen and slow to  fatigue. They are the first to be recruited, thin with lots of cytoplasm, which slows  delivery of nutrients unless the cell is thin. ex. marathon and distance events, cycling,  swimming. Usually about 50% total fibers in most people, but endurance atheletes  may have 95% Type I fibers, some people may have as few as 19%. Type I fibers  generally can not change into Type II fibers, only possible over long term. But, type  II fibers can become type I fibers. Type I fibers are about 1/10 as fast as Type IIx  fibers.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern