Physiology of Exercise

composed of the plasmalemma and the basement membrane. 

located between the plasmalemma and the basement membrane.Involved in the growth and development of skeletal muscle  and in muscle adaptation to injury, immoblization, and training. 

gelatin-like substance fills spaces within and between the myofibrils. Contains mainly dissolved proteins, minerals, glycogen, fats and necessary organells. 

extensions of the plasmalemma that pass laterally through the muscle fiber. Interconnected as pass among myofibrils, allowing nerve impulses received by plasmalemma to be transmitted rapidly to individual myofibrils 

longitudinal network of tubules found within muscle fiber. Serves as a storage site for calcium, essential for muscle contraction.

muscle fiber contains several hundred-thousand of these. Made up of the basic contactile elements of skeletal muscle- the sarcomeres. 

basic functional unit of a myofibril and basic contractile unit of muscle. Each myofibril is composed of numerous sarcomeres joined end to end at Z disks. 

An I-band (light zone)

An A band (dark zone)

an H zone ( middle of A band)

an M-line in middle of H zone

the rest of A band

a second I-band

thinner filaments 

Thicker filaments. Makes up about 2/3 of all skeletal muscle protein

stabilizes the myosin filaments along their longitudinal axis. Extend from Z-disk to the M-line. 

Actin

Tropomyosin

Troponin

anchoring protein for actin, coextends with actin and appears to play regulatory role in mediating actin and myosin interaction. 

tube-shaped protein that twists around actin strand

complex protein attached at reg intervals to both actin strands and the tropomyosin. 

nerve cell that connects with and innervates many muscle fibers. 

A single motor neuron and all the muscle fiers it directly signal 

Synapse or gap between the a-motor neuron and a muscle fiber. Where communication between nervous and muscular systems occurs. 

begins with the excitation of a motor nerve and results in contraction of the muscle fibers. 

Myosin cross-bridges are activated, bind to actin resultin in conformation change in cross-bridge, causes the myosin head t tilt and to drag thin filament toward the cener of sarcomere

Tilting of the myosin head to tilt

Energy molecule. Myosin molecule must bind with ATP for muscle contraction  to occur 

Enzyme located on myosin head, splits ATP to yield ADP, inorganic phosphate, and energy.

slow-twitch

take approx 110 ms to reach peak tension when stimulated

Most muscles composed of 50% type I fibers

high level of aerobic endurance

fast twitch

reach peak tension in about 50ms

most muscles composed 25% type IIa fibers

poor aerobic endurance

Motor units within a given muscle appear to be ranked. 

tyoe I -->type IIa --> type IIx

the order of recruitment of motor units is directly related to the size of their motor neuron. 

Motor units with smaller motor neurons will be recruited first. 

Type II motor units are recruited as force needed to perform the movement increases. 

shortening of muscle

considered a dnamic contractions

Muscles act without moving

Muscles generates force but its length remain static (unchanged), because joint angle does not change

Muscles exert force while lengthening

a dynamic contraction