BMS 300 1st Edition Lecture 27 Outline of Last Lecture I. Motor cortex and descending pathways -somatotopy on the precentral gyrus 1. motor cortex-internal capsule -decussation of the pyramids-lateral cortico spinal tract -innervation of lower motor neurons II. The motor unit-refination -the neuromuscular synapse -nicotinc acetycholine receptors -E.P.S.P-action potentialsIII. Membrane systems of skeletal muscle cells -sarcolemma -T-tubule -S.R. (sarcoplasmic reticulum) IV. The T-SR junction These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-DHP receptors-T-tubule charge sensitive -RYR receptors-SROutline of Current Lecture V. EC coupling and the sliding filament theory -from LMN to T-SR-the T-SR junction 1. DHP receptors: plug2. RYP receptors: Ca2+ release channel >Ca2+ release from SR -the cytoskeleton and its organization in to sarcomeres -components of the sarcomeres 1. thin filaments >actin>tropin (ca2+ binding) >tropomyosin 2. myosin 3. z-lines of actinin VI. Actomyosin bridges and the power stroke -myosin binding to actin -myosin as an ATPase -the power stroke 1. ADP and Pi leaveVII. Ending Recycle-pumping Ca2+ in the SR VIII. Rigonmentis Current LectureRecap last lecture: -there is a synaptic cleft with Ach vesicles inside of it >ligand gated channels are opening which means there is an influx of + charge from the Na+ -there are v-gated Na+ channels -on the other end of the cell membrane there is a sarcoplasmic reticulum inside the t-tubules (transverse tubules) -there is a dihydropyramine receptor attached to the sarcoplasmic reticulum which acts as a “plug” and the mouth of the ryanodine receptor -the positive charge pulls this “plug” out and this is how we get the Ca2+ signal to the cytoplasm Organization of the SarcomereSarcomere: the repeating unit of sirated muscle-voluntary skeletal muscle -cardiac muscle 1. Actin thin filament >filamentous actin >trophin: trophin complex -trophin C: Ca2+ binding protein 2. trophomysin >actin binding protein: ribbon like protein -z-lines (z disks): actin attachment sites -the myosin forms bundles: 100,000 or more form the myosin think filament Myofibril: repeating stacked sarcomeres -thick and thin filaments are hexagonally packed -z line to z line makes up a sarcomere -a sarcomere has thick and thin filaments There is a myosin binding site, actin monomer, trophin C, tropomyosin -trophin C: Ca2+ binding component-there is low affinity Ca2+ binding -tropomyosin: all the myosin binding sites are covered -the myosin heads try and reach up and grab the actin -the binding of Ca2+ causes the tropomyosin to turn on edge which exposes the myosin binding sites-how we get movement in the muscles -the top of the myosin head causes a release of ADP and Pi -the myosin head moves position when it binds to the actinHow do we stop this movement?-we stop delivering action potential and instead it is how ATPase Ca2+ pumps which move the Ca2+ back into the
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