MUSCLES
Muscle structure
Muscle fibers
• A single cell that
contracts in response to
stimulation
Muscle structure
Fasciculi/Fascicle
• Small compartments of
muscle tissue
• Bundles of muscle
fibers
Muscle coverings
• From inside --> out
1) Endomysium- thin covering of connective
tissue over each muscle fiber
2) Perimysium- tissue surrounding each bundle
of muscle fibers or fascicle
3) Epimysium- tissue surrounding all bundles
together
Muscle covering- Fascia
• Sheet of fibrous Connective tissue that
surrounds a muscle
• Like: sausage casing or a sweater around
muscle fibers
Muscle cell structure
Sarcolemma
• Cell membrane of a muscle cell
Sarcoplasm
• Cytoplasm of a muscle fiber,
• contains a small oval nuclei, mitochondria,
and myofibrils
myofibrils
• Key player of muscle contractions- threadlike
filling of a muscle fiber
• contains: protein filaments (myosin, and actin)
Myofibril structure
Myosin
• Thick protein filament
Actin
• Thin protein filament
Sarcomere
• The segment of a myofibril that extends from
z line to z line- unit of contraction
Belly
• Fleshy central part of the muscle
Belly
Steps of contraction
• #1- Distal end of motor neuron releases
acetylcholine
Contraction cont…
• #2 Acetylcholine diffuses across the
neuromuscular junction
Contraction cont…
• #3 The muscle fiber membrane is stimulated.
Contraction cont…
• #4 Impulse travels deep onto the muscle fiber
through the transverse tubules
Contraction cont…
• #5 Impulse reaches the Sarcoplasmic
reticulum
Contraction cont…
• #6 Calcium diffuses from the S.R. to the
sarcoplasm
Contraction cont…
• #7 Calcium unlocks binding sites on actin
Contraction cont…
• #8 Linkages form between actin and myosin
filaments
Contraction cont…
• #9 Myosin cross bridges pull actin inward
Contraction cont…
• #10 Muscle fiber shortens
contraction
• http://www.youtube.com/watch?v=gpFc48SjmI