Types of Muscle Fibers and Contractions Muscular System
Types of Muscle Fibers and Contractions
Muscular System Muscles are the organs that move body parts. ___________________. More than 600 muscles in the body – 35– 40% of body mass is muscle
Muscular System Muscle—organ that _____ and becomes shorter or _____ and becomes longer – Result = Body parts move, energy is used, and work is done.
Muscles at Work ___________________________. – One muscle contracts while the other muscle relaxes. – Muscles always ____; they never push.
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. 10 A
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.
TYPES OF MUSCLE CONTRACTIONS
Types of Muscle Contractions ________: when the ms. does not shorten during contraction while tension is increasing. Isotonic 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 2 Types: 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.
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