Flashcards in Muscles & M Tissue Slides Deck (34):
Skeletal muscle tissue is
Attached to bones
Cardiac muscle tissue
Only in the heart
Smooth muscle tissue
In walls of hollow ograns; stomach bladder, airways
Receive/respond to stimuli
Normal to larger size
Normal to 1/3 of size
Back to normal size
Movement of bones/fluids
Each muscle is served by one nerve, one artery, 1+ veins
Surrounds entire muscle; belly CT
surrounds fascicles Ct
surrounds each muscle fiber/ areolar ct
Anatomy of skeletal muscle fiber
Cylindrical, up to 30 cm
Multiple peripheral nuclei
Myioglobin- takes O2 to cells
Myofibrils, SR, T-tubules
Dense, 80% of cell volume
Thick filaments: Myosin (A Band)
Thin filaments: Actin (I band and partially to A band)
Zdisc: Anchors thin filaments
Hzone: Lighter midregion where there is no overlap
Mline: Holds adjacent thick filaments together
Two interwomen polypeptide chains
2 smaller polypeptide chains; crossbridges
Binding sites for actin filaments
Binding sites for ATP
Stores Calcium Ions
Continuous with the sarcolemma
Pentrates cell's interior at each A/I band junction
myosin heads bind to actin, detach, and bind again to propel thin myofilaments toward the M-line. Zlines move together.. A band doesn't move.
Requirements for skeletal muscle contraction
Activation: neural stimulation at neuromuscular junction
Excitation: Generation and propagation of an action potential along the sarcolemma
Trigger; rise of intracellular Ca levels
Events at neuromuscular junction
Axons of motor neurons go from CNS---> skeletal muscles via nerves. Each axon ending forms neuromuscular junction with a single muscle fiber
Midway along length of a muscle fiber.
Axon terminal and muscle fiber separated by synaptic cleft. Synaptic vessicles contain neurotransmitter Ach.
Sarcolemma contain Ach receptors
Nerve impulse arrives at axon terminal.
ACh is released and binds with receptors on the motorr end plate of the sarcolemma. Electrical events lead to a generation of an action potential.
ACh opens chemically ligand gated ion channels. There's diffusion of Na in and K out. More Na is diffused so the sarcolemmma's interior becomes less negative.
Generation and Propagation of an action potential
End plate potential spreads to adjacent membrane areas. Voltage gated Na+ channels open. Na influx decreases membrane voltage towards a critical threshold. If the threshold is reached, an action potential is generated.
Na channels close and voltage gated K channels open. K efflux rapidly restores the resting polarity.
Ionic conditions of resting state restored by calcium potassium pump.
What happens at the peak of an action potential?
Na gates will close and K gates will open.
E-C Coupling (excitation-contraction)
Sequence of events of an action potential leading to sliding of the myofilaments
lag time; time between initiation and contraction
Events of EC
Action potential is propagted along sarcomere to t-tubules
Voltage sensitive proteins stimulate release of Calcium ions from SR.
Role of calcium in contraction
Calcium binds to troponin, troponin moves tropomyiosin away from active sites on actin. Cross bridge occurs, when Nervous stimulation ceases, ca pumped back into SR and end of contraction.
Cross bridge detachment
ATP attaches to myosin head and the cross bridge detaches.