Contraction II Department of Biology, WCU.

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Presentation transcript:

Contraction II Department of Biology, WCU

Revision Sarcomere bands and zones, filaments (thick, thin)

Myosin 1. tail and heads 2. cross bridge 3. head pivots

Actin Actin 2 strands Tropomyosin stiffen actin block myosin head

Actin Troponin: 3 polypeptides Functions inhibit actin and myosin binding rotates actin to enable myosin binding binds to Ca++

Sliding filament theory Sarcomeres shorten Filament length does not shorten Filaments slide

Sliding filament theory 1. Cross bridge attachment Ca++ influx tropomyosin release myosin attachment ATP conversion

Sliding filament theory 2. Power stroke myosin head pivots disappearance of H zone and I band ADP + Pi release

Sliding filament theory 3. Cross bridge detachment detachment binding of new ATP low to high energy confirmation

Sliding filament theory Cross bridge reattachment ATP hydrolysis reattachment

Sliding filament theory One power stroke results in 1% shortening Muscles shorten by 30% Many attachments and detachments

Rigor mortis What is stimulus for myosin detachment? ATP availability Extracellular Ca++ Muscle stiffening 3 - 4 hr < 12 hr > 48 - 60 hr