Lecture 18 – Muscle Physiology VI

Cause a whole sheet of muscle to contraction no

Info icon This preview shows pages 2–4. Sign up to view the full content.

Cause a whole sheet of muscle to contraction No concept of a motor unit You can only get a graded response by controlling the force of contraction This is done by regulating the amout of Ca  2+  in the cytosol of the muscle cell phasically active cells can be autorhythmic Cross Bridge activation Activation of myosin molecule by a rise of cytosolic Ca 2+ If you get an influx of Ca 2+  from the ECF or the SR, the calcium binds to calmodulin It is inactive until Ca  2+  is bound Then calmodulin complex activates MLCK MLCK is then activated Dephosphorylates an ATP and adds that phosphate to one of the light chains Myosin 2 in smooth muscle allows P to bind to a light chain Cause the myosin to stand up and comes close enough to the actin thin filaments so  that it binds to the active sites of the actin filaments
Image of page 2

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

CB forms Will continue until the phosphate group is taken of the myosin If you pump Ca  2+  out of the cell, it changes the dynamic of the MLC-P and it will  dephosphorylate the myosin Relaxation Must dephosphorylate the myosin MLC-P is always active and catalyzing the removal of phosphate group Forward rxn of MLCK is favored by high cytosolic calcium, back reaction in the opposite High Ca  2+  concentrations make the rate of myosin phosphorylation higher than that of  the MLC-P reaction Latch State Adaptation to reduce ATP use when sustained contraction is necessary Sphincters ATP hydrolysis is taking place in the cytosol (?) and in CB cycling
Image of page 3
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