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sarcomere
contractile unit
44
Accounting
Pre-School
10/23/2012

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Term

Skeletal Muscle

Definition

Longest, striated, voluntary, responsible for overall body motility, contract readily & tires easily

Term

Cardiac Muscle

Definition

Bulk of heart walls, striated, involuntary, contracts fairly steady rate

Term

Smooth muscle

Definition

No striations, involuntary, slow sustained contractions, stomach and bladder

Term

Muscle functions

Definition

Producing movement, maintaining posture and body position, stabilizing joints, generating heat, protection

Term

Skeletal Muscle Gross Anatomy

Definition

Supplied with nerve ending, rich blood supply, need continuous delivery of oxygen, gives large amounts of waste

Term

Endomysium 

Definition

Surrounds each muscle fiber

Term
Perimysium
Definition

Surrounds a fascicle of muscle fibers

Term
Epimysium
Definition

Surrounds the whole muscle

Term
Skeletal Muscle Microscopic Anatomy
Definition

Long cylindreal cell, Multiple nuclei beneath the sarcolemma, sarcoplasm (contains glycosomes and myoglobin)

Term
Myofibrils
Definition

Each muscle fiber contains thousands, densely packed, contain sarcomeres, striations repeating series of dark a bands and light I bands

Term
H Zone
Definition

Lighter stripe in midsection of A band

Term
M Line
Definition

Dark line, dissects each H Zone vertically

Term
Z Disc/line
Definition

Darker area, Midline interruption of I band

Term
Sarcomere
Definition

Smallest contractile unit, functional unit of muscle fiber, region of myofibril between two successive z discs

Term
Thick Filaments
Definition

Extend entire length of A Band, connected in middle of sarcomere, composed primarily of protein/myosin, tail and two heads, heads link thick and thin filaments together forming cross bridges

Term
Thin Filaments
Definition

Extend across I band and partway into A Band, 2 discs anchor them, composed chiefly of protein, actin 

Term
Tropomyosin
Definition

Help stiffen and stabilize actin, arranged end to end along actin, block myosin binding sites in relaxed fiber

Term
Tropin
Definition

Three polypeptide complex: inhibitory subunit binds to actin, binds tropomyosin and helps position it on actin, binds calcium

Term
Elastic filaments
Definition

Composed of protein/titin, extends from z disc to thick filaments, runs within thick filament to M line, holds thick filaments in place, maintain organization of A band, helps muscle spring back into shape after stretched

Term
Sarcoplasmic Reticulum
Definition

Interconnecting tubules surrounding each myofibril, large number of mitochondria and glycogen granules, terminal cisterns, regulate intracellular levels of calcium

Term
Terminal Cisterns
Definition

Form large channels, at junction of A-I bands, always appear in pairs

Term
T Tubules
Definition

At each A-I band junction, continuations of the sarcolemma, protrudes deeply into muscle cell, greatly increase surface area, runs between paired terminal cisterns forming triads

Term
Sliding Filament Model of Contraction
Definition
During contraction, thin filaments slide past thick filaments
Term

Sliding Filament Model of Contraction

Relaxed muscle fiber

Definition

Thick and thin filaments overlap only at the ends of A band

Term

Sliding Filament Model of Contraction

Muscle fibers stimulated

Definition

Myosin heads latch onto actin binding sites to begin sliding, cross bridge attachments formed and broken several times

Term

Sliding Filament Model of Contraction

Occurs simultaneously in sarcomeres throughout cell

Definition

Muscle cells shorten, I band shortens, distance between successive z disc reduces, H zone disappears

Term
Skeletal fiber to contract
Definition

Stimulated by nerve ending, generate an electrical current (AP), AP transmitted along sarcolemma, intracellular calcium levels rise briefly

Term
Somatic neurons
Definition

Stimulates skeletal muscle cells, in brain or spinal cord

Term
Neuromuscular junction
Definition

Region where motor neuron comes into close contact with skeletal muscle cell

Term
Synaptic cleft
Definition
Separate axonal ending of motor neuron from muscle fiber
Term
Synaptic vesicles
Definition

Contain neurotransmitter, Ach

Term
Junction folds
Definition

Part of the sarcolemma, helps for neurotransmitter junction, highly folded giving large surface area for ach receptors

Term
How motor neuron stimulates muscle fiber
Definition

Nerve impules reach end of axon, Ach released into synaptic cleft, Ach diffused across cleft, attaches Ach receptors to sarcolemma, ach binding triggers events causing an AP

Term
Aceyticholinesterase
Definition

Enzymes in synaptic cleft, breaks down Ach, prevents continued muscle contraction

Term
Resting sarcolemma is polarized
Definition

Inside is negative relative to outer face, predominant extracellular: Sodium, predominant intracellular: potassium

Term

Generation of AP across the sarcolemma

AP result of

Definition

Generation of end plate potential, depolarization, repolarization

Term
Depolarization
Definition

Generation and propagation of AP, AP initiated, AP unstoppable, AP travels rapidly over entire sarcolemma

Term
Repolarization
Definition

Sodium channels close, potassium channels open, potassium efflux rapidly restores resting polarity

Term
Excitation-contraction coupling
Definition

Nerve impulses reaches axon terminal, voltage-gated calcium channels open, ach released into synaptic cleft, ap generated and sent, ap triggers release of calcium from SR, calcium binds to tropin changing its shape, contraction

Term
Removal of calcium
Definition

Blocks myosin binding on actin, contraction ends, muscle fiber relaxes

Term
Intracellular calcium low
Definition

Muscle cell is relaxed, active sites on actin blocked by tropomyosin, blockade removed when sufficient calcium is present

Term
Oxidative fibers
Definition

Rely on aerobic pathways

Term
Glyclotic fibers
Definition

Rely on anaerobic pathways

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