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myofibrils

composed primarily of actin and myosin

visceral smooth muscle

composed of sheets of muscles; found in walls of visceral organs; displays rhythmicity

peristalsis

rhythmic, wavelike motion produced by smooth muscles in tubular visceral organs

temporalis

closes the jaw

intercalated disks

found at the ends of cardiac muscle used to hold adjacent cells together

all-or-none response

when a muscle fiber contracts, it contracts completely

calcium

these ions combine with the troponin to change the shape of the tropomyosin so that it bonds with the cross-bridges of the myosin

pyruvic acid

molecules produced during anaerobic respiration from conversion of glucose

sarcomere

responsible for the striated apppearance of skeletal muscles

cholinesterase

enzyme that causes acetylcholine to decompose

transverse tubules

found between or on the cisternae; function is to transmit a muscle impulse into the cell interior

gluteus maximus

extends the leg at the hip

ATP

Lack of this causes muscle cramps

gastrocnemius

flexes the leg at the knee

sternocleidomastoid

pulls the head to one side

aponeurosis

broad, fibrous sheet of connective tissue that attaches the coverings of adjacent muscles

myosin

contains the cross-bridges that join actin at active sites (areas on the surface of actin that contain ADP molecules)

threshold stimulus

minimal strength of stimulation needed to cause a muscle contraction

latent period

delay between the time a stimulus is applied and the time the muscle respons

rigor mortis

occurs after death when muscles fail to relax due to a lack of ATP

liver

organ that is able to convert lactic acid into glucose

deltoid

abducts the upper arm

muscle tone

partial but sustained contraction

ATPase

the enzyme that breaks down ATP to get energy

creatine

supplies energy for the synthesis of ATP

phosphate

contracts and relaxes more slowly than skeletal muscle; cells lack transverse tubules, have a single nucleus, and is under involuntary control

orbicularis oris

puckers lips

acetylcholine

neurotransmitter released by motor neurons in order to stimulate skeletal muscle fibers

tetanic contraction

forceful, sustained muscle contraction

endomysium

separated individual muscle fibers

motor end plate

the folded muscle fiber membrane found at the neuromuscular junction

serratus anterior

pulls the scapula downward

gracilis

adducts the thigh

neurotransmitter

stored in vesicles within motor neuron endings

mitochondria

place in which aerobic respiration occurs

epimysium

outermost layer of connective tissue surrounding a skeletal muscle

synergists

muscles that assist a prime mover

motor unit

consists of a motor neuron and the muscle fibers that it controls

myoglobin

the pigment responsible for the reddish brown color of skeletal muscle

oxygen debt

amount of oxygen needed to support the conversion of lactic acid to glycogen (polymers of glucose)

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