- Slides: 10
Muscles • Skeletal Muscle • Cardiac Muscle • Smooth Muscle
Microanatomy of Skeletal Muscle
• Each muscle cell (fiber) is 10 -80 micrometer ln diameter & is covered by a cell-membrane called Sarcolemma. • Each cell contains between a few hundreds to a few thousands Myofibrils. • Each Myofibril contains 3000 Actin filaments & 1500 Myosin filaments. • Each myofibril is striated: consisting of dark bands (called A-bands) and light (I-bands).
EXCITATION –CONTRACTION COUPLING • MECHANISIM OF CONTRACTION
Muscle Contraction Summary • Nerve impulse reaches myoneural junction • Acetylcholine is released from motor neuron • Ach binds with receptors in the muscle membrane to allow sodium to enter • Sodium influx will generate an action potential in the sarcolemma
Muscle Contraction Continued • Action potential travels down T tubule • Sarcoplamic reticulum releases calcium • Calcium binds with troponin to move the troponin, tropomyosin complex • Binding sites in the actin filament are exposed
Muscle Contraction Continued • Myosin head attach to binding sites and create a power stroke • Attachment of ATP, detaches myosin heads and energizes them for another contaction • When action potentials cease the muscle stop contracting