How cross-bridge cycling occurs, however, differs between muscle
types. Which of the following highlights a difference in the
cross-bridge formation between smooth muscle and skeletal muscle?
Check all that apply.
(A) Ca^2+ induces a chemical change in myosin in the thick
filaments in smooth muscle; Ca^2+ induces a physical change in the
thin filaments in skeletal muscle.
(B) In smooth muscle, a light chain is phosphorylated so that
myosin can interact with actin; in skeletal muscle, troponin and
tropomyosin are moved so that myosin can interact with actin.
(C) Thin filaments of a contracted smooth muscle cell can pull
toward opposite ends of a thick filament, whereas all thin
filaments of a contracted skeletal muscle pull toward the center of
a thick filament.
Explain why A and C apply to this question.
1). Cardiac muscle cells are joined -------------- by
intercalated discs, which helps enhance the spread of action
potentials throughout the heart. (a) end-to-end (b)
side-by-side
2). Smooth muscles are___________ at their ends and
arranged as sheets. These characteristics help them to contract as
a single unit. (a) tapered (b) widened