11C H A P T E R

Muscle PhysiologyMuscle Physiology

Gary R. Hunter

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

A Motor UnitA Motor Unit

Sectional View of a Muscle Fiber

Sectional View of a Muscle Fiber

Detailed View of Myosin and Actin Protein Filaments in Muscle

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 MuscleContraction of a Myofibril: Stretched Muscle

Contraction of a Myofibril: Partially Contracted MuscleContraction of a Myofibril: Partially Contracted Muscle

Contraction of a Myofibril: Completely Contracted MuscleContraction 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 ActionsForce-Velocity Curve for Eccentric and Concentric Actions

Three Arrangements of Muscle FibersThree Arrangements of Muscle Fibers

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.