BIO* - Biology BIO* M121 Lecture Notes - Lecture 14: Sliding Filament Theory, Sarcomere, Troponin
9 Jun 2020
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The contraction of the muscle is dependent on how the sarcomeres shorten. Sarcomeres lengthen when the cell relaxes and an external force stretches the muscle. The z disk forms the end wall of the sarcomere. The actin (thin) and myosin (thick) filaments slide past one another during a contraction. The sliding filament model explains important aspects of sarcomere contraction. When a sarcomere contracts, the lengths of the thin filaments (from a to c) and thick filaments (from b to d) do not change. Rather, the filaments slide past one another. During contraction, a and b move closer to each other, as do c and d. Each myosin molecule consists of two subunits with their tails coiled together and their two heads exposed. The heads contain binding sites for atp and actin. When one of these subunits binds, its myosin head changes shape. Atp binds to the myosin head, causing a shape change that releases the head from actin.
