A&P chapter 9
Orgin
attachment to immovable bone
fasicles
bundles of muscle fibers
Sarcoplasm
cytoplasm of a muscle cell
terminal cistern
enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules.
direct
epimysium fused to periosteum of bone or perichondrium of cartilage
junctional folds
folded regions of the sarcolemma at the neuromuscular junction
sarcomere
functional unit of skeletal muscle, smallest contractile unit of muscle fiber
elastic filaments
hold thick filament in place and helps muscle cell spring back into shape after stretching
aerobic endurance
length of time a muscle can contract using aerobic pathway
Dystrophin
links thin filaments to the sarcolemma
concentric contraction (isotonic)
muscle shortens during the contraction; ex. flexing, picking up a book
acetylcholine receptors
on junctional folds
Sarcolemma
plasma membrane of a muscle fiber
neuromuscular junction
point of contact between a motor neuron and a skeletal muscle cell
Role of the Z disk
protein sheath that anchors the thin filaments, they mark the ends of the sarcomere
myoglobin
red pigment that stores oxygen
Myofilaments
rod like structure inside sarcomeres
tendon
rope like made of tough collagen fibers
Triads
runs between two terminal cisterns of the SR forming a triad . They are continuous with sarcolemma, they conduct nerve impulses to the deepest regions of the muscles cell and trigger the release of calcium for the SR
synaptic vesicles
sac that contains the neurotransmitter acetylcholine
synaptic cleft
space between the axon terminal and the sarcolemma of the muscle fiber
Aponeurosis
strong sheet of tissue that acts as a tendon to attach muscles to bone
somatic motor neuron axon
the axon of the somatic motor neuron
indirect
the muscle CT wrapping extends beyond the muscle either as a rope like tendon or sheet
anaerobic threshold
the point at which muscle metabolism converts to anaerobic glycolysis
crossbridge
this forms when the myosin heads attach to actin during muscle contraction
T tubules
tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side
Describe how a motor neuron signals a muscle fiber
1. Nerve impulse arrives at the axon terminal of the motor neuron 2. Calcium channels open and extracellular calcium enters the axon terminal 3. calcium entry causes ACh to be released by exocytosis 4. Ach diffuses across the synaptic cleft and binds to arch receptors on the sarcolemma of the muscle cell 5. ACh opens ion channels that allow sodium ions into the cell and potassium ions out of the cell. causes depolarization which is needed to begin a nerve impulse across the sarcolemma
Two binding sites found on myosin head
1. actin binding site 2. atp binding site
myofibrils
Rod-like strands of contractile filaments Many sarcomeres in series
sacroplasmic reticulum
Specialized endoplasmic reticulum in muscle cells; stores and releases calcium ions
Acetylcholine (ACh)
A neurotransmitter that enables learning and memory and also triggers muscle contraction
Tropomyosin
A protein of muscle that forms a complex with troponin regulating the interaction of actin and myosin in muscular contraction
Troponin
A protein of muscle that together with tropomyosin forms a regulatory protein complex controlling the interaction of actin and myosin and that when combined with calcium ions permits muscular contraction
Myosin
A protein present in muscle fibers that aids in contraction and makes up the majority of muscle fiber
Endomysium
Connective tissue surrounding a muscle fiber
Somatic motor neurons
a motor neuron of the somatic nervous system. A somatic motor neuron stimulates voluntary muscle
Epimysium
a sheath of fibrous elastic tissue surrounding a muscle.
insertion
The attachment of a muscle tendon to a moveable bone or the end opposite the origin
perimysium
The connective tissue that surrounds fascicles.
eccentric isotonic contraction
When the length of a muscle increases during a contraction
Strations
Microscopically visible lines formed by alternating light and dark bands along fibers.