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Page 1: Muscular Contractions

MUSCULAR CONTRACTIONS

Contracting and Relaxing Skeletal Muscle

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Anatomy of a Muscle Fiber (Cell)

Sarcolemma Myofibril Sarcomere Z line

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Anatomy of a Sarcomere

Actin Myosin

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Contraction Overview

Lovely artwork courtesy of David Goodsell and the RCSB Protein Data Bank

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Steps of a Muscle Contraction

Nerve causes release of acetylcholine (ACh)

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Steps of a Muscle Contraction

Reception of ACh causes an action potential (electrical nerve signal) in muscle cell

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Steps of a Muscle Contraction

Action potential causes release of calcium in muscle cell

Meanwhile…

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Steps of a Muscle Contraction

Calcium binds, forming troponin complex and revealing myosin binding sites.

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Steps of a Muscle Contraction

Sliding filament theory

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Contraction Overview

Lovely artwork courtesy of David Goodsell and the RCSB Protein Data Bank

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Relaxation

Acetylcholinesterase breaks down Ach Active transport prepares the muscle cell for

future action potentials Active transport removes free calcium from

muscle cells ATP breaks actin-myosin linkage

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Relaxation

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Interference

Botox & botulism – block acetylcholine release

Rigor mortis – can’t keep calcium out of cells so muscles contract, lack of ATP prevents myosin from releasing actin