Muscle Contraction and Relaxation

Muscle Filaments

• Actin is the major constituent of thin filaments in muscle cells.
• Myosin is the major constituent of thick filaments in muscle cells.

Muscle Contraction

• Muscle tension can be produced without changes in muscle length due to the simultaneous contraction of multiple muscle fibers.
• The termination of muscle contraction is followed by relaxation.

Muscle Contraction Theory

• The Sliding Filament Theory explains how protein filaments within each skeletal muscle fiber slide past each other to produce a contraction.

Muscle Contractions in Vertebrates

• Skeletal muscle contractions in vertebrates are neurogenic, requiring synaptic input from motor neurons.

Muscle Fiber Contraction

• When muscle fibers contract at the same time due to innervation by a single motor neuron, it is called synchronized contraction or a motor unit.

Post-Contraction Process

• After muscle contraction, the process of muscle relaxation follows, which involves a return of the muscle fibers to their low tension-generating state.