Lecture 7: Skeletal Muscle Tissue and Muscle Organization

myofilaments

are made of myosin and actin

sarcomeres

consist of myofilaments

myofibrils

consist of sarcomeres

muscle fibers

consist of myofibrils

muscle fasicles

consist of muscle fibers

skeletal muscle

consist of muscle fasicles

epimysium

covers entire skeletal muscle

perimysium

surrounds muscle fiber bundles (fascicles)

endomysium

surrounds individual muscle fibers/cells

A band - dArk band

band that contains thin and thick filaments

I band - light band

that contains only thin filaments

M line, H band, Zone of overlap

A band contains

M line

in the center of A band

H band/zone

area in A line that ONLY HAS THICK FILAMENTS

Zone of Overlap

zone that thin and thick filaments overlap

I band

where the thin (actin) filaments attach to one another

propogates along sarcolemma

Once action potential is generated it

it travels down T tubules to triads

after the ap propogates along sarcolemma

release of Ca from the terminal cisternae of SR

after traveling down to triads AP causes

Ca binds to troponin and changes shape (closes clip)

After Ca 2+ is released from SR

troponin moves tropomyosin (clip moves hair), exposing active sites on thin filaments

after shape change of troponin

contraction cycle is initated

after active sites are exposed