Muscle Tissue Flashcards by J K

Skeletal Muscle
(S, F, L)

Structure: composed of long, striated multinucleated muscle fibers; limited ability to renew

Function: production of major movements of the body

Location: all over the body; most are attached to bones

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Cardiac muscle
(S, F, L)

Structure: composed of short, striated, uninucleate cardiomyocytes with branched cytoplasm, firmly attached to each other via intercalated discs; inability to renew, contains glycogen storage

Function: coordinated contraction and relaxation fills and pumps blood; glycogen stores for energy

Location: heart

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Smooth muscle
(S, F, L)

Structure: composed of short, fusiform, uninucleate smooth muscle cells staggered in parallel; able to renew continually; homogenous eosinophilic cytoplasm (no striations or bands)

Function: coordinated contraction of the visceral organs

Location: visceral organs; gastrointestinal tract (GI blood vessels, exocrine glands, etc.)

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Regeneration in skeletal muscle

Satellite cells in skeletal muscles have limited ability to proliferate and differentiate into skeletal muscle cells; as a result, extensive injury and destruction of muscle tissues cannot be fully repaired; muscle building exercises causes muscle fibers to grow, not to increase in number

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Skeletal muscle fiber
(S, F, L)

Structure: striated, multinucleated muscle cell

Function: individual contractile cell

Location: throughout the muscle

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Endomysium
(S, F, L)

Structure: thin reticular fibers

Function: structural support for each cell and delivery of small vessels and nerves

Location: surrounds each muscle fiber

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Fascicle
(S, F, L)

Structure: A bundle of muscle fibers

Function: functional unit that works together

Location: throughout the muscle

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Perimysium
(S, F, L)

Structure: connective tissue

Function: bind together fascicles and help it function as a unit, deliver larger vessels and nerves

Location: surround each fascicle

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Named muscles
(S, F, L)

Structure: formed from a collection of fascicles

Function: work in a coordinated manner to create movements

Location: throughout the body

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Epimysium
(S, F, L)

Structure: dense connective tissue

Function: sheath the muscle, help transmit contractile force of the muscle, deliver major vessels and nerves

Location: surround each muscle

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Myofibril
(S, F, L)

Structure: thin and long bundles that fill the muscle fiber

Function: contractile structure as long as the muscle cell

Location: throughout sarcoplasm

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Sarcomere
(S, F, L)

Structure: contractile unit of the myofibril

Function: line up back to back to form a myofibril

Location: length of the myofibril

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Myofilaments
(S, F, L)

Structure: strands of protein polymers; myosin (thick filaments) and actin (thin filaments)

Function: Interaction between thick and thin filaments produces contraction; overlap between the two filaments creates a banding pattern (striations)

Location: within each sarcomere

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Sarcoplasmic reticulum
(S, F, L)

Structure: network of specialized sER surrounds each myofibril. Terminal cisternae are dilated portions of the sarcoplasmic reticulum

Function: store, release, and reuptake Ca++

Location: throughout the sarcoplasm surrounding each myofibril; terminal cisternae are located between A and I bands

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Transverse tubules (T-tubules)
(S, F, L)

Structure: invagination of the sarcoplasmic reticulum (sarcoplasm??)

Function: Transmit membrane depolarization throughout the sarcoplasm; trigger Ca++ release from terminal cisternae

Location: travel through the muscle fiber at A and I junctions

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Triad
(S, F, L)

Structure: Unit of two terminal cisternae with a T Tubule in the middle

Function: effective depolarization wave transmission and release of Ca++

Location: A and I junctions

A band
(S, F, L)

Structure: dark band

Function: span of thick filaments; areas of overlap with thin filaments on either side

Location: middle portion of sarcomere

H band
(S, F, L)

Structure: less dark band in the middle of the A bad

Function: portion of A band with only thick filaments

Location: middle portion of the A band

M line
(S, F, L)

Structure: Faint, thin line in the middle of the A band

Function: Anchor thick filaments in place

Location: middle of A band

I band
(S, F, L)

Structure: light band

Function: area with only thin filaments

Location: lateral portion spanning two sarcomeres

Z line (Z disc)
(S, F, L)

Structure: dense line in the middle of the I band

Function: Anchor thin filaments and mark the boundary of the sarcomere

Location: end margin of each sarcomere; midline of the I band

Neuromuscular junction
(S, F, L)

Structure: Site of interaction between the motor axon terminal (highly branched, contains numerous ACh filled vesicles) and receptor region on sarcolemma (shallow depression with many membrane folds and junctional folds expressing receptors for ACh)

Function: In response to action poetical the motor axon terminal releases ACh into the synaptic cleft; the ACh receptors bind ACh and initiate membrane depolarization wave throughout the muscle fiber

Location: Usually in the middle of the muscle fiber but may vary

Motor Units

A group of skeletal muscle fibers innervated by a single motor neuron that contract together

Small motor unit

A small group of muscle fibers innervated by a single motor neuron that generates fine, delicate movements quickly. Includes extrinsic eye muscles and muscles that control the fingers

Large motor units

A large group of muscle fibers innervated by a single motor neuron that generates a large contractile force but is relatively slow to respond as a whole. Includes the muscles of the back, thighs, and buttocks.

Muscle contraction process

Action potential travels down the axon --> triggers release of Ach at a neuromuscular junction --> Ach binds receptors on the sarcolemma at NMJ --> Sarcolemma depolarization wave travels through the rest of the cell and T-tubules --> terminal cisternae release Ca++ --> Ca++ allows interaction of myosin and actin by binding to troponin and releasing tropomyosin from the actin ---> ATP is used to slide the filaments on each other ----> Shortens sarcomere, shortening myofibril and resulting in muscle contraction

Muscle fiber types

Type I - red, slow twitch fibers Type Ila - intermediate fibers Type IIb - white, fast-twitch fibers

Type I Muscle fibers (Slow twitch) (S, F, L)

Structure: small diameter, red appearance in vivo due to high myoglobin content; many mitochondria Function: slow to contract but resistant to fatigue; undergo oxidative phosphorylation to produce maximum ATP Location: postural muscles; large amount in muscles of endurance athletes

Type IIa Muscle fibers (Intermediate) (S, F, L)

Structure: Medium-sized diameter; slightly red due to a good amount of myoglobin; many mitochondria; glycogen storage Function: faster to contract and fairly resistant to fatigue; generate ATP by both oxidative phosphorylation and glycolysis Location: Large amount in mid-distance runners and swimmers

Type IIb Muscle Fibers (fast twitch) (S, F, L)

Structure: Large diameter; light pink in vivo due to less myoglobin; fewer mitochondria; large glycogen storage Function: Fast to contract and prone to fatigue; generate ATP rapidly by anaerobic glycolysis. Lactic acid by-products cause fatigue Location: Extraocular muscles, muscles of the fingers; large amount in short distance runner and weight lifters

Intercalated discs (S, F, L)

Structure: dark bands between cardiomyocytes Function: create cardiomyocytes syncytium; allows for the chemical and electrical communication between cells Location: in between cardiomyocytes

Transverse portion of cardiomyocytes (S, F, L)

Structure: contains adhesion junctions and desmosomes Function: adheres cardiomyocytes end to end Location: portions of the disc perpendicular to the long axis of the cell (filaments)

Lateral portion of cardiomyocytes (S, F, L)

Structure: contains gap junctions Function: transmission of macromolecules and ions between cells Location: portions of the intercalated disc parallel to the long axis of the cell

Diad | S, F, L

Structure: a unit of one terminal cisternae and one T-tubule Function: effective depolarization wave transmission and release of Ca++ Location: level of Z-lines

Dense bodies (S, F, L)

Structure: A group of proteins on the cytoplasmic side of sarcolemma Function: attach and anchor thin filaments to sarcolemma Location: scattered throughout the cytoplasmic side of sarcolemma