CHAPTER Muscle Physiology 1 Chapter Outline Skeletal muscle

CHAPTER Muscle Physiology 1

Chapter Outline Skeletal muscle macrostructure and microstructure Sliding-filament theory of muscular contraction Fiber types Types of muscle action Force production

Three Types of Connective Tissue: Epimysium, Perimysium, and Endomysium

A Motor Unit

Sectional View of a Muscle Fiber

Detailed View of Myosin and Actin Protein Filaments in Muscle

The discharge of an action potential from a motor nerve signals the release of calcium from the sarcoplasmic reticulum into the myofibril, causing tension development in muscle.

Contraction of a Myofibril: Stretched Muscle

Contraction of a Myofibril: Partially Contracted Muscle

Contraction of a Myofibril: Completely Contracted Muscle

Calcium and ATP are necessary for myosin cross-bridge cycling with actin filaments.

Type II, or fast-twitch, muscle fibers are capable of developing higher forces than Type I, or slow-twitch, muscle fibers— especially at higher velocities of muscle action.

The number of cross-bridges that are attached to actin filaments at any instant in time dictates the force production of a muscle.

Force-Velocity Curve for Eccentric and Concentric Actions

Three Arrangements of Muscle Fibers parallel to tendon Unipennate muscle Bipennate muscle

Many factors may affect rate of cross-bridge cycling and thus force, including neural activation, calcium concentration, myosin ATPase activity, preloading, prestretch, muscle fiber type and ultrastructure, fatigue through a variety of mechanisms, and number of contractile components (myosin and actin) in parallel.