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50 Cards in this Set

  • Front
  • Back
Muscles are the machinery used by the body to convert _____ _____ ____ ____ into ______ _____ that is used to do work.
-high-energy phosphate bonds (ATP)
-mechanical energy
What is the instruments of the central nervous system (CNS) that are used to alter and interact with the environment?
-Muscles
How does an action potential excite muscle fibers so they contract?
-By causing a dramatic increase in intracellular calcium
Called Excitation-Contraction (EC) Coupling
-Process that links depolarization of the muscle to an increase in intracellular calcium
End Plate Potential
-Local depolarization of the muscle fiber membrane
-Normal: 50-75 mV
Why is triggering action potentials by direct stimulation more difficult than that of a nerve?
-there is a more negative resting potential and greater membrane capacitance
The resting membrane voltage is primarily determined by ____ permeability, with a significant contribution from _____.
-K+
-P(Cl)
What is the relationship between a single AP and muscle tension?
-Because of Afterpotential and twitch
Afterpotential (def)
-the depolarized plateau of a muscle ( the rest of AP looks like that of a nerve)
Twitch (def)
-Muscle tension transient
-a peak after a brief but significant delay
Sarcomeres (def)
-the fundamental contractile unit delimited by Z disks
2 Proteins sets in Sarcomeres
-Thick and Thin Filaments
Thin Filaments Composition
-Primarily Actin
-Regulatory Proteins: Troponin and Tropomysin
G-actin
-globular actin molecule
F-actin
-globular molecules (G-actin) self assemble into the thin filaments
The thin filaments of adjacent sarcomeres are joined together at the ___ ____.
-Z line
In the thin filaments, _____ polymerizes like two strings of beads that wind _____ around each other.
-actin
-helically
What part of the sarcomere contains the thick filaments? What is it comprised of?
-A band
-myosin molecules
Actin filaments have _____ _____ that can interact with the myosin molecule.
-Active Sites
How is the interaction between actin and myosin prevented in the absence of calcium?
-Tropomysin covers active sites
What does calcium binding to troponin trigger?
-A series of conformational and molecular interactions that effect sarcomere and force generation.
How does sarcomere shortening occur?
-As the filaments "slide" past one another
What are force and sarcomere shortening attributed to?
-Interaction between thick filament myosin heads with thin filament actin molecules to form "Transfilament crossbridges"
Crossbridges allow the filaments to _____ and _____ towards one another.
-Grip
-Pull
What type of energy is used to drive the contraction process?
-Energy liberated from ATP hydrolysis by enzymatic activity present on the myosin heads
Tetrodotoxin (def)
-a toxin that blocks Na+ channels and suppresses APs
Is an AP required for a contractile event?
-No
-Use of tetrodotoxin: injected into to cell=transient increases in intracellular calcium
_______ alone is sufficient to increase the intracellular calcium concentration to levels required for contraction
-Depolarization
Sarcolemma (def)
-Cell membrane that surrounds a muscle fiber
Muscle fibers contain ______.
-Myofibrils
What make up an myofibril?
-Composed of the individual contractile filaments
Sarcoplasmic Reticulum (def)
-A bag-like structure that encircles a myofibril
T-tubule System (def)
-Surround the myofibril
-Narrow invaginations of the sarcolemma that run deep inside the muscle fiber to form an elaborate plasma membrane network
-Brings T-tubules in close proximity to a pair of adjacent terminal cisternae of the sarcoplasmic reticulum
Triad (def)
-2 Adjacent terminal cisternae of the Sarcoplasmic reticulum
-T-tubule
An elevation in cytosolic ______ level triggers muscle contraction.
-Calcium
Resting cytosolic calcium concentration measurements is ______ and during contraction it may increase ______ to ______.
-.1uM
-20-fold
-2 uM
____ serves as a reservoir for calcium and that APs in the sarcolemma act to trigger the release of this store calcium.
-Sarcoplasmic Reticulum
What do T-tubules provide for the muscle fiber?
-A communication from the outside to the deep interior of the muscle fiber
-Provides synchronization of calcium release from SR stores, synchronized sarcomere shortening and contraction
T-tubule membranes possess the necessary ____ and ____ channels for AP propagation
-Na+
-K+
The T-tubules contain a high density of ______ ____ ____ ______.
-Voltage-Gated calcium channels
Voltage-Gated Calcium Channels (T-Tubules)
-Act as a receptor for derivatives of 1,4-dihydropuridines
1,4-dihydropuridines
-Clinical agents used to treat both hypertension and angina pectoris
Calcium channels in t-tubules are also referred to as _______ ____.
-Dihydropyridine receptors (DHPRs)
Why are SR calcium release channels also called ryanodine receptors?
-The plaint alkaloid ryanodine binds to them with high affinity and locks them in the open condition
2 Groups of Muscles
1. Striated
2. Smooth
2 Types of Striated Muscles
1. Skeletal
2. Cardiac
Types of Smooth Muscle
-Vascular and Gastrointestinal
Does skeletal muscle require calcium for contraction?
-No
Calcium channels are _____ _____ for skeletal muscle.
-Voltage sensors
Voltage-Gated Calcium release mechanism (VGCR)
-the calcium channels present in the T-tubules "sense" the change in membrane voltage during an action potential