Chapter 8:
Skeletal Muscle
Part 1

EXERCISE PHYSIOLOGY

Skeletal Muscle

Human body contains over _______ skeletal muscles

–_____-______% of total body weight

Functions of skeletal muscle

–____________ production for locomotion and breathing

–Force production for _____________ support

–______________ production during cold stress

Connective Tissue Covering Skeletal Muscle

Epimysium

–________________________

Perimysium

–________________________

Fascicles

Endomysium

–Surrounds individual muscle fibers

Connective Tissue Covering Skeletal Muscle

Microstructure of
Skeletal Muscle

______________________: Muscle cell membrane

______________________ Threadlike strands within muscle fibers

Actin (_________ filament)

Myosin (_______ filament)

Sarcomere

•Z-line, M-line, H-zone, A-band & I-band

Within the sarcoplasm

–________________ ________________

Storage sites for calcium

Transverse tubules

Terminal cisternae

______________________

Within the Sarcoplasm

The Neuromuscular Junction

Where __________ ______________ meets the muscle fiber

Motor end plate: pocket formed around motor neuron by sarcolemma

Neuromuscular cleft: _________ ________

Ach is released from the motor neuron

Causes an end-plate potential (EPP)

Depolarization of muscle fiber

Neuromuscular Junction

Muscular Contraction

The sliding filament model

Muscle ___________________ occurs due to the movement of the actin filament over the myosin filament

Formation of ________________________ between ___________ and ______________ filaments “Power stroke”

1 power stroke only shorten muscle 1%

–Reduction in the distance between ________________ of the sarcomere

The Sliding Filament Model

Actin & Myosin Relationship

Actin

Actin-binding site

___________________ with calcium binding site

Tropomyosin

Myosin

–Myosin head

–Myosin tais

Actin & Myosin Relationship

Energy for Muscle Contraction

_________ is required for muscle contraction

Myosin ATPase breaks down ATP as fiber contracts

Sources of ATP

–_________________ (PC)

–__________________

–_______________ ___________________

Excitation-Contraction Coupling

Depolarization of motor end plate (excitation) is coupled to muscular contraction

Nerve impulse travels down T-tubules and causes release of Ca⁺⁺ from SR

_________ binds to _____________ and causes position change in tropomyosin, exposing active sites on actin

Permits strong binding state between actin and myosin and contraction occurs

Steps Leading to Muscular Contraction

Biochemical properties

–Oxidative capacity

–Type of ATPase

Contractile properties

–Maximal force production

–Speed of contraction

–Muscle fiber efficiency

Individual Fiber Types

Fast fibers

•Type ________ fibers

–Fast-twitch fibers

–Fast-glycolytic fibers

Type _________ fibers

–Intermediate fibers

–Fast-oxidative glycolytic fibers

Slow fibers

Type ______ fibers

–Slow-twitch fibers

–Slow-oxidative fibers

Muscle Fiber Types

Comparison of Maximal Shortening Velocities Between Fiber Types

Histochemical Staining of Fiber Type

Fiber Typing

Gel electrophoresis: myosin isoforms

–different weight move different distances

Fiber Typing

Immunohistochemical:

–Four serial slices of muscle tissue

–antibody attach to certain myosin isoforms

Muscle Tissue: Rat Diaphragm