25 terms

A&P Muscular System

delicate connective tissue membrane that covers specialized skeletal muscle fibers
tough connective tissue binding together fascicles
coarse sheath covering the muscle as a whole
point of attachment that does not move when the muscle contracts
point of attachment that moves when the muscle contracts
prime mover
a muscle or group of muscles that directly performs a specific movement
muscles that, when contracting, directly oppose prime movers; relax while prime mover in contracting to produce movement; provide precision and control during contraction of prime movers
muscles that contract at the same time as the prime movers; they facilitate prime mover actions to produce a more efficient movement
fixator muscles
joint stabilizers
plasma membrane of muscle fibers
sarcoplasmic reticulum
network of tubules and sacs found within muscle fibers, stores calcium ions within its sacs
numerous fine fibers packed close together in sarcoplasm
segment of myofibril between two successive Z lines, myofibrils consists of many of these, contractile unit of muscle fibers
triplet of tubules; allows an electrical impulse traveling along a T tubule to stimulate the membranes of adjacent sacs of the sarcoplasmic reticulum
T tubule
sandwiched between two sacs of sarcoplasmic reticulum
within myofibrils, thick and thin; thin attach to both Z lines of a sarcomere and extend part way toward the center; thick do not attach to the Z lines
motor unit
motor neurons plus the muscle fibers to which it attaches
twitch contraction
a quick jerk of a muscle that is produced as a result of a single, brief threshold stimulus
the staircase phenomenon; gradual, step like increase in the strength of contraction that is seen in a series of twitch contractions that occur 1 second apart
smooth, sustained contractions
isotonic contractions
contraction in which the tone or tension within a muscle remains the same but the length of the muscle shortens (same tension)
isometric contraction
contraction in which muscle length remains the same while the muscle tension increases (same length)
first class
fulcrum lies between the pull and the load, not abundant in the human body, serve as levers of stability
second class
load lies between the fulcrum and the joint at which the pull is exerted, presence of these levers in the human body is a controversial issue
third class
pull is exerted between the fulcrum and load, permit rapid and extensive movement, most common type of lever found in the body