lecture_notes_16_(ta) - Lecture 16 Muscle Physiology...

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Lecture 16: Muscle Physiology Reading: chapter 8, section: skeletal muscle, pgs 259-269 (pgs 263-273, if using 5 th edition) ( TA NOTES IN RED ) -Review of the Neuromuscular Junction (NMJ) Structures involved in conducting signals from the NMJ to the interior of the muscle cell Transverse Tubule - invagination of the plasma membrane at each sarcomere (Figure 8-10) . ( EXTRACELLULAR TUBE THAT GOES THROUGH THE CELL , LIKE THE HOLE OF A DONUT . K NOWN ALSO AS A T- TUBULE , AN ACTION POTENTIAL TRAVELING ACROSS THE PLASMA MEMBRANE ( SINCE THAT S WHERE THE VG-N A + CHANNELS ARE ) WOULD ALSO TRAVEL THROUGH THE T- TUBULES AND PENETRATE DEEPER INTO THE MUSCLE CELL ) Sarcoplasmic Reticulum - modified endoplasmic reticulum composed of a fine network of interconnected tubules into which Ca ++ is actively transported ( AND STORED ) (Figure 8-10) . ( LIKE AN INTRACELLULAR C A ++ SPONGE ) Lateral Sacs - enlarged regions of the sarcoplasmic reticulum that come into close contact with the transverse tubules. Foot Proteins - proteins that span the gap between the lateral sacs and the transverse tubules and mediate a change in permeability to Ca ++ by the lateral sacs. Also known as ryanodine receptors because they are locked open by the plant chemical ryanodine. ( THESE ARE IMPORTANT SINCE THEY CAN LET C A ++ OUT OF THE SARCOPLASMIC RETICULUM ) Dihydropyridine ( DI - HYDRO - PY - RID - I - DINE ) Receptor - receptor proteins in the transverse tubule membrane that come into contact with the foot proteins. They are voltage dependent and gate the change in permeability of the foot proteins to Ca ++ . ( THESE TELL THE FOOT PROTEIN TO RELEASE C A ++” INTO THE CYTOPLASM )
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Excitation-Contraction Coupling (Figures 8-7,8-8,8-9,8-11,8-12) Muscular contraction occurs when the thick and thin filaments within a sarcomere slide past one another. This sliding action is mediated by a complex sequence of chemical reactions called the power stroke that utilizes the hydrolysis of ATP as an energy source and is dependent on the release of intracellular stores of Ca ++ from the sarcoplasmic reticulum. (note, the list below is more complete than that shown in figure 8-12)
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lecture_notes_16_(ta) - Lecture 16 Muscle Physiology...

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