Muscles Part 1 Flashcards
Muscle Tissue is derived from
Mesoderm
Three types of muscle tissue
Skeletal
Cardiac
Smooth
Skeletal Muscle Tissue contains
40% of body mass
multi-nucleated cells
quick twitch, short contractions
Cardiac Muscle Contains
cells are short and branched
striations
intercalted discs
intermediate twitch
Smooth Muscle Tissue Contains
Lack striations
Slow twitch
long contrations
Functions of Skeletal Muscle Tissue
Produces Skeletal Movement
Maintains Body Posture and Positon
Supports Soft Tissues
Guards Entrances and Exits
Maintains body temperature
Provides Nutrient Reserves
A Single Skeletal Muscle is composed of
Large bundles called fascicles
Fascicles are composed of
Numerous Muscle Cells also called Muscle Fibers
Muscle Fiber is composed of
Myofibrils
Myofibrils are composed of
Two Contractile proteins called myofilaments
Myosin
Thick Myofilaments
Actin
Thin myofilaments
Sarcomeres
Myocin and Actin are arranged in an overlapping pattern creating hundreds to thousands of these
Epimysium
Dense Layer of Collagen Fibers surrounds the entire muscle
Separates Muscle from surrounding tissues and organs
Connected to Deep Fascia
Perimysium
Fibrous layer that divides muscle fibers into a series of bundles called fascicles
Possesses blood vessels, nerves, collagen and elastic fibers
Endomysium
Delicate connective tissue that surrounds individual skeletal muscles/fibers
Tendon
End of skeletal muscles collagen fibers merge into this
Aponeurosis
Broad sheet at end of muscles, anchor to bone
Cytoplasm of a muscle cell is called
Sarcoplasm
Myogobin
Large amounts in muscle cells
Important protein in storage of oxygen
Plasma Membrane of a muscle cell is called
Sarcolemma
Transverse Tubules (T tubules)
Invaginations of the sarcolemma that extend deep into the sarcoplasm at right angles to cells surface
Allow electrical impulses generated at the surface to travel into the cell’s interior
Sarcoplasmic Reticulum (SR)
Similar to smooth ER of other cells
Forms tubular network surrounding each myofibril
Membrane contains ion pumps that move Calcium from cytosols into the ER
Calsequestrin
Protein located in the SR that calcium ions bind to
Triad
One T-Tubule that has a terminal cisterna on either side
Terminal Cisterna
Tubules of SR that are enlarged and form chambers to store calcium ions
Sarcomere
Functional/contractile unit of skeletal muscle
Resting length of about 2 um
Composed of specific arrangements of myofilaments of actin and myosin
A Band
Dense region of sarcomere that contains overlapping thick (myosin) and thin (actin) filaments
I Band
Either side of A band
Only contains thin filaments (actin)
H Band
In the middle of the A- Band
Only contains Thick filaments (myosin)
M Line
Located in Middle of H band
Anchors central portion of each thick filament
Z Lines
Mark Boundary between adjacent sarcomeres
Actinins
Located in Z line
Proteins
Anchor thin filaments of adjacent sarcomeres
Numbers 1-5
1 - Muscle Fiber Nucleus
2 - Motor Neuron Axon
3 - Axon Branches
4 - Motor Neuron Endplate
5 - Myofibril of muscle fiber
Numbers 6-10
6 Synaptic Cleft
7 Folded Sarcolemma
8 Acetylcholine
9 Mitochondria
10 Synaptic Vesicles
Thin Filaments of Actin are composed of
F-Actin Filamentous Actin
G-Actin Globular Actin
Nebulin
Tropomyosin
Troponin
F-Actin
Filamentous - Twisted strand composed of two rows of 300-400 individual molecules of G-Actin
G-Actin
Globular
Rounded, compact molecule of protein that possesses an active site where one myosin molecule can bind
Nebulin
Long strand of protein that extends along the F-Actin strand in the cleft between the rows of G-Actin molecules
Helps stabilize the F-Actin strands
Tropomyosin
Double-stranded protein that covers over the active sites of the G-Actin in a resting muscle. Prevents interaction of actin and myosin
Troponin
Three globular subunits, strategically placed along tropomyosin
Action of Calcium biding to Troponin
Troponin changes shape which causes tropomyosin to swivel, revealing active site on G-Actin so myosin and actin can form a cross bridge
Myosin
Myosin Molecules - pair of myosin subunits twisted around each other
Tail portion connected to a free head portion
Tail and Free head connected by hinge that allows head to swivel
Single filament has about 300 molecules twisted together - tails point to M Line, heads arranged in a spiral facing the thin filaments
At core is a thick elastic filament of Tintin which recoils after stretching
Synaptic Terminals
Axon of each motor neuron branches to form numerous cellular extensions
