lect 5 --muscle

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University of Toronto Scarborough
Biological Sciences
Stefan Rusyniak

LECTURE 5muscle y Skeletal muscle can span entire length of the muscle y Come across some terminology not used frequently any more o Sarcosomemuscle fibremito wn muscle fibrewont be used this on a test o SarcomuscleOf these 4 only one Stephan using is sarcoplasmic reticulumER of muscle is very specialized stores calcium crucial to muscle contractionSRcalcium storage vessel y More complex then just actinmyosin Tropomyosin and troponin cover binding sites on actin Have to move that complex away so the binding sites for myosin head groups are exposed so myosin can bind to actin o Actinthin Myosinthick 2300 myosin filaments lrg aggregation of protein o Sarcomere is fcnal unit of muscle Single sarcomere small but the additive effect of multiple sarcomeres in myofibril has significant strengtho There are other accessory proteins holding myosin and actin in place o Multiple myofibirls make up a muscle fibre o Skeletal muscles have further hierarchy individual muscle fibres bundled into a fascicle And then attached to bonethat attachment is a tendon y Composition of muscle o Myocyte major cell in muscle Myoblast is immature will fuse with other oneso Will have connective tissue because u need some way of transmitting muscle contraction to a tendonfibroblasts present as wello Transmitting contraction to tissuemuscle fibre itself wrapped in connective tissue and that is continuous with the tendon Collagen enters into connective tissue surrounding each fibre o Fascia brings in vascl so see lots of capillaries wn fascia also provides attachment pt bn muscle and boneo Attachment provided by protein complexes that attach sarcomeres in myofibrils to cell membrane and go on to attach cell memb to underlying basal lamina and therefore the connective tissue These protein complexes called dystrophins muscle dystrophy caused by mutations in these poretein complexes so there isnt connections betwn muscle fibres and fascia so not transmitting these msgs trhough connective tissue to other muscles Muscular dystrophy is based on attachment of cell to facia and that mean u cant transmit contraction and transmitting that to the tendons that connect the bones Muscular dystrophyweakness o ECMType 1 collagenIn delicate layers between muscle fibres can be reticular fibres Req some elastic fibres bn in fascia because when u stretch muscles u also stretch fascia need it to be able to recoilPurkinje FIBRE not cell Found in cardiac muscle and purkinje cell is a neuron in ur cerebellumy Properties of muscle o Muscle cells display the following propContractilitybecause of actin and myosin found in cells So they can shortenExcitabilityrespond to electrical stimuli Neurons can carry action potentials but muscles can maintain electrical gradients and s
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