Name the following movements: ◦ Increasing angle of joint (ex. Straightening arm) ◦ Moving around longitudinal axis: ◦ Moving a limb away from midline.

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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