Name the following movements:◦ Increasing angle of joint (ex. Straightening arm)◦ Moving around longitudinal axis:◦ Moving a limb away from midline of body:
BELLWORK
Microscopic Structure and Muscle Contraction
Muscle Fascicle (Muscle bundles) Muscle fibers (muscle cells) Myofibrils Myofilaments (thick and thin)
Muscle Structure
Cell membrane of skeletal muscle cells
Sarcolemma
1 muscle fiber = many myofibrils 1 myofibril = many thick and thin filaments The thick and thin filaments form the
smallest functional unit of muscle the sarcomere
Microscopic Structure
Made of proteins◦ Structural: make up the structural framework of
muscles◦ Contractile: involved in the process of contraction◦ Regulatory: not part of contraction, but they
regulate it
Thick and Thin Filaments
Actin (thin filament) has binding sites for myosin
Myosin & Actin
1950s – scientists observed that the length of thick and thin filaments stayed the same during muscle contraction
This led to the Sliding Filament Theory:◦ During muscle contraction, the thick and thin
filaments do not shorten, but slide on one another which results in the shortening of the sarcomere and the entire muscle
Sliding Filament Theory
1. Myosin head binds to ATP 2. Myosin head gets energized
Sliding Filament Theory
3. Crossbridge forms between myosin head and actin
Sliding Filament Theory
4. Power stroke causes filaments to slide
Sliding Filament Theory
5. Another ATP molecule binds to myosin head causing it to release from actin and return to original position
Sliding Filament Theory
http://www.youtube.com/watch?v=Ct8AbZn_A8A
Sliding Filament Theory
How is the sliding filament theory similar to these doors?
Sliding Filament Theory
Troponin and Tropomyosin (regulatory proteins) depend on Calcium ions
Troponin: has binding site for calcium ions Tropomyosin: covers binding site on actin
Regulation
What would happen if there are no Calcium ions present?
Calcium ions
6 most important chemicals (molecules):◦ Myosin, actin, tropomyosin, troponin, ATP,
Calcium
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