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22 Cards in this Set

  • Front
  • Back
-Specialized contractilce elements
-80% of volume of MF
-cylindrical intracellular structures 1um in diameter
-extend the length of the MF
-highly organized cytoskeletal elements (thick/thin)
-thin filament
-thread like proteins
-lie end-to-end alongside the groove of actin spiral
-covers the actin sites that bind with cross bridges=blocking the interaction that=muscle contraction
Contractile Proteins
-actin and myosin> yet neither actually contracts
-binding actin and myosin at cross bridges=energy consuming contraction of the MF
Excitation-Contraction coupling
series of events linking muscle excitation (presence of AP in MF) to muscle contraction (cross-bridge activity=thin filaments to slide closer together to produce sarcomere shortening)
the functional unit of skeletal muscle
-thin filament
-protein complex
-3 polypeptide units
1. one that binds to tropomyosin that binds to actin
3. one that can bind with Ca2+
*When NOT bound to Ca2+, stabalizes tropomyosin in blocking position over actin's cross bridge binding sites
*When bound, shape protein changes, no blocking
T Tubules
-transverse tubule
-formed when surface mem. dips into MF
- runs perpendicularly from surface of muscle cell mem into center of MF
-AP spreads down into it=rapid transmition of electic activity to center of fiber
> AP=permeability changes in sarcoplasmic reticulum
Neuromuscular junction
-at axon terminals when connecting with muscle
-a junction with muscle cells
motor unit
-team of concurrently activated components
-one motor neuron+all MF it innervates
-MF that make motor neuron are thoughout whole muscle; simultaneous contraction=evenly distributed (weak) contraction of whole muscle
-in excitation-contraction coupling it's released from terminal of motor neuron and initiates an AP in muscle cell that's propagated over entire surface of muscle cell mem.
Sarcoplasmic Reticulum
-modified ER
-network of interconnected compartments surrounding each myofibril (mesh sleeve)
-encircles myofibril throughout its length, NOT continuous
-segments wrapped around A bands and I bands
-lateral sacs store Ca2+
-spread of AP down T tubule triggers release of Ca2+ to cytosol
3 forms of muscle
1. skeletal
2. cardiac
3. smooth
*all have specialized contractile apparatus made up of thin actin filaments that slide relative to stationary, thick myosin filaments in response to a rise in cytosolic Ca2+ to accomplish contraction
* all directly use ATP
Skeletal Muscle
-striated by a highly organized internal arrangement
-A and I bands
-cross bridges
-Voluntary muscle
Cardiac Muscle
Smooth Muscle
Levels of organization in skeletal muscle
Whole Muscle->MF->myofibril->think and thin filaments->myosin and actin

(organ,cell,specialized intracellular structure, cytoskeletal elements, proteins)
Sliding filament theory if muscle contraction
thin filaments on each side of sarcomere slide inward over stationary thick filaments toward the A band's center. As they slide inward, thin filaments pull Z lines to which they are attached closer together;sarcomere shortens. As all sarcomeres shorten simultaneously, the entire fiber becomes shorter
Twitch summation
When the two twitches resulting from the two Ps add together to produce greater tension in the fiber than that produced by a single AP
-similar to temporal summation of EPSPs at the postsynaptic neuron
2 primary factors that can be adjusted to accomplish gradation of whole-muscle tension
1. the number of muscle fibers contracting within a muscle
2. the tension developed by each contracting fiber
-When the muscle fiber is stimulated so rapidly that it doesn't have a change to relax between stimuli
-a smooth, sustained contraction of max strength
-2 or 4 times stronger than a single twitch
Length-Tension relationship
p. 272
Force-Velocity relationship
p. 275