Skeletal Muscle

attaches to bone via tendons, striated, contracts, voluntarily controlled

epimysium, perimysium, endomysium

connective tissue layer which surrounds the entire skeletal muscle system; outter

connective tissue that surrounds the fascicle; around

bundles of skeletal muscle fibers

connective tissue that surrounds each skeletal muscle fiber (cell) w/in a fascicle

cellular unit of skeletal muscle

sarcolemma, transverse (T) tubules, sarcoplasm

plasma membrane of a skeletal muscle fiber

folds of sarcolemma that extend into the interior of a skeletal muscle fiber

cytoplasm of a skeletal muscle fiber

nuclei, mitochondria, sarcoplasmic reticulum (SR)

multinucleate- many nuclei in skeletal muscle fiber

several fused precursor cells

produce ATP(energy); required for muscle contraction

ER of skeletal muscle fiber; membraneous sac stores (Ca+2) ions- muscle relaxation & releases (Ca+2) ions into sarcoplasm to initiate muscle contraction

glycogen & myoglobin

storage form of glucose; break dwn into glucose to make ATP; found in liver

reddish protein that stores O2 & releases it when needed by mitochondria to generate ATP

rodlike structures; cause skeletal muscle fiber to shorten (contraction); 2 types thick filament, thin filament

thick filament, thin filament

contain the protein myosin

contain 3 types of proteins; actin, troponin, tropomyosin

repeating unit of myofibrils; consist of 5 regions- Z disc, A band, I band, H zone, M line

composed of a-actin proteins; distance between 2 successive Z discs defines sarcomere

dark area, extends length of thick filament; includes parts of thin filament that overlap thick filament

light area, extends from Z discs on either side; includes part of thin filament that do not overlap thick filament

central part of A band; contains only thick filament, dark

central part of H zone; consist of myomesin, interconnect neighboring thick filaments

long protein, extends from each half of sarcomere; connect Z disc to M line; flexible, stretch & snap back; structural support

protein that links thin filaments to proteins in sarcolemma; pull sarcolemma causes skeletal muscle fiber to shorten; structural support

cause movement of various parts of the body; pull on tendons, in turn pulls on the bone, causes movement

myosin molecules; 2 polypeptide chains that form a rodlike tail & double head; 2 binding site- actin-binding site & ATP-binding site

3 proteins- actin, tropomyosin, troponin

thin filament, form double stranded actin helix; myosin-binding site-myosin head can attach to cause contraction

rod-shaped protein, promotes skeletal muscle relaxation; covers myosin-binding sites on actin- prevents myosin from interacting with actin

globular protein, promotes skeletal contraction; Ca+2 ions released into sarcoplasm, binds to troponin, pushes tropomyosin off myosin-binding sites on actin, interact(contraction)

myosin heads attach to & "walk" along the thin filaments at both ends of sarcomere, pulling the thin filament towards the M line; thin filament slides inwards & meet at center of sarcomere

ATP hydrolysis, attachment of myosin to actin, power stroke, detachment of myosin from actin

hydrolyzes ATP into ADP & phosphate group; energy generated stored in myosin head-energized

energized myosin heads attach to myosin-binding site on actin; only 1 head binds at a time

myosin head attaches to actin during contraction cycle

after crossbridge is formed, myosin head pulls thin filament past thick filament towards center of sarcomere, generating tension(force); uses energy stored in myosin head

as ATP binds to the ATP-binding site on myosin head, it detaches from actin; myosin hydrolyzes newly bound ATP; (continues as long as ATP avaliable & Ca+2 level is high)

consist of a motor neuron & skeletal muscle fibers it innervates; motor neuron elicts A.P. all fibers contract together

site of communication between a motor neuron & skeletal muscle fiber (presynaptic cell & postsynaptic cell)

synaptic end bulbs of the motor neuron, motor end plate, synaptic cleft

contain synaptic vesicles filled w/ neurotransmitters (acetylcholine, ACh)

sarcolemma of the skeletal muscle fiber; contains ACh-receptors that bind to ACh

space between synaptic end bulb of motor neuron & motor end plate of the skeletal muscle fiber

release of acetylcholine, activation of ACh receptors, production of muscle action potentials, termination of ACh activity

nerve a.p. at endbulb of motor neuron causes synaptic vesicles to undergo exocytosis, synaptic vesicles fuse w/ motor neuron's plasma mem., releasing ACh into synaptic cleft, diffuses across synaptic cleft

binding of ACh to receptor on motor end plate opens an ion channel in ACh receptor, small cations (Na+) flow across mem.

inflow of Na+, makes inside of muscle fiber more (+), change triggers muscle A.P., then propagates along sarcolemma into T tubule system, causing muscle fiber to contract

ACh no longer released when A.P. in motor neuron ceases, ACh is broken down by enzyme acetylcholinesterase(AChE), prevents formation of another A.P.

enzyme which breaks down the molecules of ACh into acetyl & choline

sequence of events connecting muscle A.P. to muscle contractions

transfer of phosphate from creatine phosphate to ADP to form ATP, anaerobic glycolysis, aerobic (cellular) respiration

immediate source of ATP, 15 seconds;

small molecule similar to an amino acid in structure; found in skeletal muscle fibers & cardiac muscle fibers

transfers 1 of the phosphate groups of ATO to creatine to form creatine phosphate when ATP is in excess

break down of creatine, forming a nitrogenous waste product

source of ATP when a skeletal muscle fiber lacks O2 or doesnt have enough O2 to meet metabolic needs (weight-lifting)- 2 min

source of ATP when skeletal muscle fiber has plenty of O2 (resting, walking, moderately running on treadmill)- several min to hr or more