Download Muscle Physiology

Muscle Physiology
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).
Z line
Z line
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