Types of Muscle Fibers and Contractions http://commons.wikimedia.org/wiki/File:Skeletal_System.png http://commons.wikimedia.org/wiki/File:Muscular_system.svg

Muscular System Muscles are the organs that move body parts. _________________ ___________________. More than 600 muscles in the body 35–40% of body mass is muscle http://commons.wikimedia.org/wiki/File:Souplesse_exercice_du_tendon_d%27Achille.png

Muscular System Muscle—organ that __________ and becomes shorter or __________ and becomes longer Result = Body parts move, energy is used, and work is done. http://commons.wikimedia.org/wiki/File:Bicep_tricep.gif

Muscles at Work _________________________________________________________________. One muscle contracts while the other muscle relaxes. Muscles always ________; they never push. http://commons.wikimedia.org/wiki/File:Bicep_tricep.gif

Motor neurons and muscle contraction Motor neurons stimulate muscle contraction Motor neurons are branched and can stimulate more than one muscle fiber _________________________________________________________ _________________= the synapse between a motor neuron and a muscle fiber

Fig 30.10A

Motor neurons and muscle contraction The strength of a muscular contraction is controlled by the number of motor units activated. _________________________________________________ Muscles requiring precise control have one motor neuron per muscle fiber

Muscles at Work Results of Muscle Action Muscles contract This produces thermal energy, and it uses chemical energy. Thermal energy produces heat that helps keep body temperature constant. Chemical energy is from glucose. (When glucose is used up, muscles are tired and need to rest.)

Muscles at Work Results of Muscle action (cont.) Over time, muscles become _______ or _______, depending on how much work they do. http://commons.wikimedia.org/wiki/File:RIAN_archive_103479_Soviet_weight-lifter_Viktor_Mazin_during_the_XXII_Olympic_Games.jpg

TYPES OF MUSCLE CONTRACTIONS

Types of Muscle Contractions ________________: when the ms. does not shorten during contraction while tension is increasing. Isotonic contraction: _________________________________________________________________________________.

Isometric Contraction Isotonic Contraction Isometric Contraction Tension is constant Tension n the ms. Rises markedly Length is decreased or lengthened ______________________ _________________ No work is done less energy used/muscle contraction More energy used/muscle contraction

Types of Isotonic Contractions Concentric: ___________________________________________________________________________________ Eccentric: ______________________________________________________________________________________

Slow- and Fast-Twitch Fibers Skeletal muscle fibers can be divided on basis of contraction speed: ______________________ Fast-twitch (type II fibers). Differences due to different myosin ATPase isoenzymes that are slow or fast.

Slow- and Fast-Twitch Fibers Slow-twitch (type I fibers): Red fibers (high myoglobin content). ___________________________________________________ Resistant to fatigue. ________________. Numerous mitochondria and aerobic enzymes.

Slow- and Fast-Twitch Fibers Fast-twitch (type IIB fibers): _______________________ Adapted to respire anaerobically. Have large stores of glycogen. _________________ Have few mitochondria.

Slow- and Fast-Twitch Fibers Intermediate (type IIA) fibers: ________________ Resistant to fatigue. People vary genetically in proportion of fast- and slow-twitch fibers in their muscles.