3Muscle fibers/cells Terminology for cell structure 12.2 Skeletal Muscle Fiber ContractionMuscle fibers/cellsTerminology for cell structureThe plasma membrane is called the ___________.The cytoplasm is called the _____________.The SER of a muscle cell is called the ______________________ and stores calcium.
4Muscle fibers/cells Terminology for structure within a whole muscle 12.2 Skeletal Muscle Fiber ContractionMuscle fibers/cellsTerminology for structure within a whole muscleMuscle fibers are arranged in ___________ called fascicles.Myofibrils are bundles of myofilaments that run the length of a fiber._______________ are proteins (actin and myosin) that are arranged in repeating units.______________ are the repeating units of actin and myosin found along a myofibril.4
6The sarcomere Made of 2 protein myofilaments 12.2 Skeletal Muscle Fiber ContractionThe sarcomereMade of 2 protein myofilamentsA thick filament is composed of several hundred molecules of the protein myosin. Each myosin molecule is shaped like a ____ ____Primarily, a thin filament consists of 2 intertwining strands of the protein actin.These filaments _____ over one another during muscle contraction.
8The beginning of muscle contraction: The sliding filament model 12.2 Skeletal Muscle Fiber ContractionThe beginning of muscle contraction: The sliding filament modelNerve impulses travel down a motor neuron to a _____________________._______________ (ACh) is released from the neuron and binds to the muscle fiber.This binding stimulates the fiber causing ____________ to be released from the sarcoplasmic reticulum.
10Muscle contraction continued… 12.2 Skeletal Muscle Fiber ContractionMuscle contraction continued…Released calcium combines with ___________, a molecule associated with actin.This causes the ______________ threads around actin to shift and expose myosin binding sites._______ heads bind to these sites forming cross-bridges.______ binds to the myosin heads and is used for energy to pull the actin filaments towards the center of the sarcomere – contraction now occurs.