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Muscles
 There are three types of muscle cells
 _____________, ____________, and ______________
 All muscles can ___________ (shorten)
 When muscles contract, part of the body __________
Cardiac Muscles
 ___________, tubular, and branched
 Have one nucleus per cell
 Contract ____________________
 Found in the walls of the ___________
Smooth Muscles
 _______________, arranged in sheets
 Have one nucleus per cell
 Contract __________________ and can sustain prolonged
contractions
 Found in the walls of ______________ organs (cavities and tubes)
such as:
 Blood vessels, iris of the eye, internal organs such as the
stomach, intestines, uterus, and esophagus for peristalsis
Skeletal Muscles
 _____________ and tubular
 Have many nuclei per cell
 Attached to the bones of the skeleton
 Contract _______________, controlled consciously by the nervous
system
 Due to structure and having many nuclei, they are referred to as
__________
Type
Cardiac
Structure
Voluntary/Involuntary Location in Body
Smooth
Skeletal
 Muscle Contraction
 Muscles _________, they _____________
 Muscles can only _______ they cannot push
 Muscles that permit movement are found in _______, as each
muscle in the relaxed state needs an opposite muscle to stretch
it
 ____________________ muscles – pairs of muscles that
work against each other to make a joint move
 Skeletal muscles consist of many bundled muscle fibers held together
with connective tissue
 Muscle fiber consists of:
 ________________ a thread of contractile proteins found
within muscle fibers
 _________ filament – fine myofilament composed of
bundles of protein called _________. Each myosin
molecule consists of two polypeptide chains wrapped
around each other. Binds to actin.
 _______ filament – fine myofilament composed of
strands of protein called _______. Consist of globular
actin proteins. Binds to myosin.
 Myofilament Contraction
 Four Steps
 Myosin head is attached to actin
 Myosin head flexes, advancing the actin filament
 Myosin head releases and unflexes, powered by ATP
 The myosin reattaches to actin farther along the fiber
Sliding Filament Model
 Actin is anchored in the striated muscle tissue called the Z-Line
 Since it is ‘anchored’ like this, when actin moves it drags the Z-line
with it, toward the myosin
 This causes the entire muscle to contract
 The heads of the two ends of the myosin filament are orientated in
opposite directions. When the heads attach to the actin, they bend
toward the center of the myosin.
 As one end of the myosin filament draws the actin filament and its
attached Z line toward the center, the other end of the myosin
filament does the same
 Both Z lines move toward the center, and contraction occurs