Flashcards in Muscle Tissue Part 1 Deck (74):
Most important characteristics of muscles tissue
Contractility and Conductivity
What gives muscle tissue it's ability to contract?
Actin, myosin, ATP
3 major types of muscle cells
Skeletal, smooth, cardiac
Characteristics of skeletal muscle
Attached to the skeleton, voluntary, *cross-striations*, used for locomotion/respirations. Quick acting but tire fast. Multi-nucleated.
Characteristics of Smooth muscle
Primarily in walls of internal organs. No striations. Involuntary
Characteristics of Cardiac muscle
Branching striated tissue. Found only in the heart. Involuntary.
Specialized plasma membranes of muscle tissue
Cytoplasm of the muscle cell
Specialized endoplasmic reticulum of muscle cells
Origin of skeletal muscles
Myoblasts of the embryonic mesenchymal cells
Skeletal muscle fiber
Each fiber is a cell. Multinucleated syncytium
Long processes formed by the sarcolemma that carry the action potential deep into the sarcoplasm
Where are the nuclei of skeletal muscles found?
Peripheral and immediately deep to the sarcolemma
What does the sarcoplasm of skeletal muscle contain?
Myofibrils, filamentous mitochondria, myoglobin, sarcoplasmic reticulum
Contractile filaments are in the myofibrils that gives the striated appearance
Lie between the myofibrils and close to the sarcolemma. Are the the source of ATP for myofibrils
Oxygen-binding protein in skeletal muscle cells
Specialized form of SER. Used for deposit of Ca. Releases Ca into the cytoplasm initiating muscle contraction
Thin filaments of muscle fiber
F-Actin, Tropomyosin, Troponin Complex
How are muscle fibers arranged?
Forms the double-stranded helical filament (is the polymerization of G-actin)
Forms filaments that lie in the groove between 2 actin monomers. Masks the myosin-binding sites on actin filament.
Attached to tropomyosin. Has Troponin T, I, C subunits
Binds to tropomyosin, anchoring the complex
Binds to actin
Binds to Ca (essential part of muscle contraction). Smallest subunit.
Thick filaments of muscle fiber
What does Myosin II consist of?
2 heavy chains: α-helices
2 globular heads: ATPase and motor activity
2 light chains: attach to heads
Where are the binding sites for ATP and actin?
Thick filament myosin II globular heads
What are the dark bands of myofibril made of ?
What are the light bands of myofibril made of?
What are the areas of A-bands?
H-zone and M-line
Part of A-bands that contains ONLY thick filaments
Dense line that bisects the H-zone. Formed by accessory protein (myomesin). Holds thick filaments in register
Pale area formed primarily by thin filaments. Is bisected by Z-disk
Composed of accessory proteins (α-actinin). Provides anchoring points for thin filaments. Supports architecture of myofibrils
Portion of the myofibril between 2 adjacent Z-disks. Basic contractile unit of skeletal muscle.
In what muscle fiber unit does muscle contraction take place?
What bands change during muscle contraction?
I-band, H-zone shrink
What band(s) do NOT change during muscle contraction?
What maintains precise alignment of thick and thin filaments of muscle fibers?
Accessory proteins, make up less than 25% of total muscle fiber protein
8 types of accessory proteins
α-actinin. Nebula. Tropomodulin. Titin. Myomesin. C-protein. Desmin. Dystrophin.
Short, bipolar, rod-shaped protein. Actin-binding. bundles thin filaments into parallel arrays and anchors them at the Z-line
Elongated, inelastic proteins. Attached to Z-lines and runs parallel to thin filaments. Helps α-actinin anchor thin filaments. Regulates length of thin filaments during muscle development
Small, actin-binding protein (actin-capping). Attached to the free portion of the thin filament. Maintains/regulates length of sarcomeric actin filament.
Large protein. Forms elastic lattice that anchors filaments in the Z-line. 2 "springs" off of the protein help stabilize the centering of the myosin-containing thick filament. Prevents excessive stretching of the sarcomere.
Myosin-binding protein. Holds thick filaments in line at the M-line
Myosin-binding protein. Holds thick filaments in line at the M-line. Forms several distinct transverse stripes on either side of the M-line.
Type of intermediate filament. Forms lattice that surrounds the sarcomere at the level of the Z-lines, attaching them to one another/plasma membrane. Forms stabilizing cross-links between neighboring myofibrils
Large protein. Links laminin in external lamina of the muscle cell to the actin filaments
Mutations in the structural proteins of skeletal muscle. Results in severe muscle weakness, muscle atrophy, and destruction of muscle fibers.
Duchenne's muscular dystrophy
Absence of dystrophin protein
Membrane Triad components
Formed by scarcoplasmic reticulum. One T-tubule and 2 cisternae
Formed by deep invaginations of the sarcolemma. Allows impulse to travel down the cell and excite terminal cisternae. Run at junction of A and I bands
Formed by the sarcoplasmic reticulum. Run parallel to T-tubules on both sides (triad formed). Contain high [Ca++]. Run near the boundary of A and I bands.
What does an action potential cause in the sarcolemma/sarcoplasmic reticulum?
Descends down along the T-tubules, causing the release of Ca++ into the sarcoplasm.
What ion's influx causes muscle contraction?
What does Ca++ bind to in the sarcoplasm and what does it do?
Troponin C, causing the spatial configuration of troponin to change, moving it away from the myosin-binding sites on the actin
What does myosin use to move along the actin filament?
Stage 1 of contraction cycle
Attachment: rigor configuration
Myosin head is tightly bound to the actin molecule of the thin filament (ATP is absent)
Lack of ATP causes myosin to remain bound to actin
Stage 2 of contraction cycle
Release: ATP induces conformational changes to the myosin head, so myosin is released from actin
Stage 3 of contraction cycle
Bending: ATP is broken into ADP and Pi (inorganic phosphate). Myosin head bends
Stage 4 of contraction cycle
Force generation: Myosin head binds to actin again. Power stroke happens. Forces actin filament along the thick filament
Release of Pi from myosin head causes head to generate a force and returns to its initial position
Stage 5 of contraction cycle
Reattachment: myosin head is attached to new actin and is ready for a new cycle
Relaxation of skeletal muscle
Ca++ activated ATPase pumps transport Ca to the sarcoplasmic reticulum. Ca disassociates from troponin C. Troponin returns to initial configuration blocking the actin/myosin interaction.
Which cells cause regeneration of skeletal muscle?
What are the actions of satellite cells?
Activated after injury, proliferate, give rise to mew myoblasts. Myoblasts fuse to form new fiber
How do muscles respond to aging?
Increase in diameter
How do muscles respond to exercising?
How do muscles respond to disuse?