A&P chapter 9

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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.


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