lecture7-11 - Lecture 7-skeletal Mechanics Lecture...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Single muscle fiber: the muscle produces tension to exert a force on the load. •if tension > load, the muscle will shorten ( isotonic contraction •If the fiber generates tension, but does not shorten (load > tension), this is isometeric contraction . lengthening contraction occurs when the muscle generates tension but still lengthens because the load > tension (such a lowering a heavy object). Why is this important? Because cross-bridging cycles in these three types of contractions is different . •Only in the isotonic contraction do the Z lines move together (and the fiber shortens). •A muscle fiber can be activated, the myosin can go through repeated rounds of ATP hydrolysis and actin binding and release, without actually moving the Z-lines closer. But tension is still generated by the actin and myosin. Lecture 7-skeletal muscle mechanics not surprisingly, the heavier the load on a muscle, the slower is the shortening velocity load
Image of page 1

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

View Full Document Right Arrow Icon
myoplasmic [Ca 2+ ] twitch force (tension) time (msec) contraction time •a single action potential results in a sub-maximum contraction ( twitch ). Myoplasmic [Ca 2+ ] falls before maximum contractile force is obtained. myoplasmic [Ca 2+ ] Repeated Action Potentials can be Summated: tetanus force • a maintained contraction in response to repeated stimulation is called tetanus •the action potential is very brief compared to the duration of the contraction •there is a short latent period between the end of the action potential and the onset of tension. •the length of the contraction time varies with muscle fiber type (see later in lecture). •if action potentials occur rapidly enough, saturating [Ca 2+ ] is achieved and maximum force is generated. Factors that regulate the strength of a single fiber contraction (twitch). •action potential are all or none, so size of action potential not a factor • rather, strength of contraction is controlled by the frequency of action potentials •repeated, but slower deploarizations will not give fused tetnus, but can be added to increase force: action potential
Image of page 2
The force generated by a muscle fiber depends upon its length: •maximum force is generated when maximum cross bridges are formed: too short , thin filaments overlap, heavy chains hitting Z-lines.
Image of page 3

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

View Full Document Right Arrow Icon
Image of page 4
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