Muscles

3 types of skeletons

endoskeleton, exoskeleton, hydrostatic skeleton

skeletal muscles are attached in _____

antagonistic pairs

skeleton functions

support, protection, movement

sarcomeres

the basic contractile units of muscles composed of thick myosin protein and thin actin protein filaments that slide past each other

myofibrils

formed by sarcomeres lined together — organelle-like structure within the cytoplasm of a muscle cell

muscle fiber cell

myofibril bundles — single nucleated cell

fascicles

muscle fiber cells bundled together by connective tissue — extends past the fibers to form tendons

muscle

fascicles together

motor unit

a single motor neuron and all the muscle fibers it controls

acetycholine

the neurotransmitter transmitting signal to muscle

recruitment

process by which more and more motor neurons are activated

tetanus

smooth and sustained contraction produced when the rate of stimulation is so high that muscle fibers cannot relax between stimuli

cardiac muscle

found only in the heart — consists of striated cells electrically connected by intercalated disks — involuntary and can generate action potentials without neural input

smooth muscle

found mainly in walls of hollow organs such as those of the circulatory, digestive, and reproductive systems — lacks striations because actin and myosin filaments are not regularly arrayed