Chapter 7: The Muscular System Flashcards
Epimysium
outermost layer of collagen fibers that surrounds the entire skeletal muscle
Perimysium
Connective tissue surrounding a fascicle
Fascicle
bundle of muscle fibers
muscle fiber
a single muscle cell
Endomysium
surrounds each muscle fiber; ties adjacent muscle fibers together
sarcolemma
muscle cell membrane
sarcoplasm
cytoplasm of a muscle cell
Transverse tubules (T-tubules)
openings scattered across the surface of the sarcolemma that lead into terminal Cisternae
Important for initiation of excitatory process to release Ca2+
myofibrils
long, cylindrical protein structures that make up muscle fibers; bundles of myofilaments
myofilaments
make up myofibrils; constructed from proteins, principally myosin and actin
sarcoplasmic reticulum
specialized smooth endoplasmic reticulum, releases calcium on demand when the muscle fiber is stimulated to contract
A band
contains thick filaments (myosin)
I band
thin filaments only (actin); shortens during contraction
synaptic cleft
The narrow gap that separates the presynaptic neuron from the postsynaptic cell
motor unit
a motor neuron and all the muscle cells it stimulates
recruitment
the activation of more and more motor units
isotonic contraction
muscle shortens or lengthens because muscle tension exceeds load
-concentric or eccentric
isometric contraction
no shortening; muscle tension increases but does not exceed load
creatine phosphate
energy storage molecule used by muscle tissue; the phosphate from creatine phosphate can be removed and attached to an ADP to generate ATP quickly
Anaerobic
without oxygen; the length of time that muscle contractions can be supported by glycolysis and existing energy reserves of ATP and CP
aerobic
with oxygen; the length of time that a muscle can continue to contract while being supported by mitochondrial activities
terminal cisternae
enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules; store excess calcium
glycolysis
the breakdown of glucose by enzymes, releasing energy and pyruvic acid
Myoglobin
oxygen-storing, red-pigmented protein in slow-twitch muscle fibers
Masseter
chewing muscle
Buccinator
“trumpeter”; compresses cheek
cross bridges
myosin head; binds to an active site and pivots toward the center of the sarcomere, pulling the thin filament in that direction
summation
the addition of one twitch to another
incomplete tetanus
muscle produces almost peak tension during rapid cycles of contraction and relaxation
complete tetanus
occurs when the rate of stimulation is increased until the relaxation phase is completely eliminated, producing maximum tension
muscle fatigue
caused by exhaustion of energy reserves or accumulation of H+ ions in the (EC) fluid; muscle can no longer contract despite continued neural stimulation
origin
beginning of muscle; remains stationary
insertion
The attachment of a muscle tendon to a moveable bone or the end opposite the origin
hamstring
biceps femoris, semitendinosus, semimembranosus
muscle naming
orientation of muscle fibers, structural features, by shape/length/size/visibility from surface (superficial vs. deep)
sarcomere
contractile units within myofibrils; the smallest functional unit of a muscle
