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Muscular System (Functions of Muscle Tissue (Skeletal muscle (generate…
Muscular System
Functions of Muscle Tissue
Skeletal muscle
produce movement of skeletal bones
maintain posture
stabilize joints by working together with tendons
generate heat
shivering & exercise
Cardiac muscle
produce movement in skin & blood
increase/decrease blood flow in blood vessels
Smooth muscle
produce movement forward of contents in hollow organs
Sphincter muscle
open/close passageways
rounded, smooth or skeletal muscle
innvoluntary
Properties of Muscle Tissue
Contractility
muscles shorten & pull on bone to move
generate force that produces contraction
pulls on attachment (insertion) point
actin protein found in muscle for movement
also moves cell membranes
Excitability
responds to stimulus
produces its own electrical signal
Extensibility
ability to stretch within limits without damage
Elasticity
ability to return to its original length after extending
Anatomy of Skeletal Muscle
Epimysium
muscle covering
dense irregular connective tissue
Perimysium
surrounds a fascicle
between fascicles are blood vessels
Endomysium
surrounds each muscle cell/fiber
Myofibrils
organelles
individual strands inside muscle cell/fiber
Sarcolemma (membrane)
Mitochondria
Sarcoplasmic reticulum
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Transverse (T) tubule
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Sarcomere
section of a myofibril
unit of contraction
several sarcomeres make up a myofibril
Sliding filament theory
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reticular connective tissue
most superficial
dense irregular connective tissue
Anatomy of Neuromuscular Junction
Neuron
Dendrites
receives messages from other cells
Axon
sends messages to other cells
Axon terminals
connects to muscle fiber
sends electrical impulses to muscle fiber
Cell body & Nucleus
electrical impulse traveling in axon to axon terminal
triggers release of chemical messenger (neurotransmitter) in exocytosis
neurotransmitter diffuses across the synaptic cleft
neurotransmitter binds with protein receptors in sarcolemma
electrical impulse generated by muscle fiber/cell & travels along sarcolemma
travels into T-tubules
triggers release of calcium from terminal cisterns of sarcoplasmic reticulum
triggers myosin heads to grab the actin and pull it toward the M line
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Motor Unit
one motor neuron & all muscle fibers it controls
some motor units have a few dozen muscle fibers
produce fine movement
ex: fingers/hands & eyes
other motor units have hundreds to thousands muscle fibers
produce coarse movement
ex: limb muscles