Chapter 9: Muscles and Muscle Tissues (B)
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Created by:
snakesayan on October 20, 2010
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Classes:
Anatomy & Physiology I & II, Honors Anatomy and Physiology 2012-2013
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56 terms
Terms | Definitions |
|---|---|
 Sarcolemma | like plasma membrane polarized; their is a potential voltage difference across the membrane and the inside is negative relative to the outer membrane face |
| Action Potential | electrical charge which occurs along the entire surface of the sarcolemma; 3 steps involved for this to occur |
| Generation of an Action Potential Across the Sarcolemma (1) |  (local depolarization and generation of an end plate potential); Binding of ACh molecules to ACh receptors at neuromuscular junction opens (ligand) gated ion channels that allow Na+ and K+ to pass; More Na+ diffuses in then K+ diffuses out and interior of sarcolemma becomes less negative (depolarization [local electrical event called, end plate potential) |
| Polarized | -70 (resting plasma potential) |
| Depolarized | 30 (for action potential to occur) |
| Generation of an Action Potential Across the Sarcolemma (2) | (generation and propagation of the action potential); [neuron send AP through axon] end plate potential ignites AP that spreads in all directions from neuromuscular junction across sarcolemma; this depolarization (end plate potential) spreads to adjacent membrane areas and opens voltage gated sodium channels; Na+ enters and reaches voltage threshold (+30), and an action potential is generated. AP is propegated along length of sarcolemma as depolarization wave spreads to adjacent areas of sarcolemma and opens voltage gated sodium channels there; again, Na+ difusses into cell |
| Generation of an Action Potential Across the Sarcolemma (3) |  (repolarization); sarcolemma is restored to intitial polarized state; Na+ channels close and voltage-gated K+ channels open; K+ efflux rapidly restores the resting polarity; Fiber cannot be stimulated and is in a refractory period until repolarization is complete; Ionic conditions of the resting state are restored by the Na+-K+ pump |
| Excitation-Contraction Coupling | Sequence of events that convert s action potentials in a muscle fiber to a contraction; Action potential travels across entire sarcolemma; occur during hidden (laten) period, between AP initiation and the beginning of mechanical activity (contraction); electrical signal does not act directly on myofilaments (it causes rise in intracellular calcium ion concentration that allows filaments to slide) |
| Excitation-Contraction Coupling: Step 1 |  action potential travels across entire sarcolemma and are rapidly conducted to interior of muscle fibers by transverse tubules |
| T Tubules | Regularly spaced infoldings of sarcolemma that branch extensively throughout the muscle fiber; At numerous junctions, make contact with calcium storing membranous network known as sarcoplasmic reticulum |
| Terminal Cisternae | formed by SR (On portion of t tubule and adjacent terminal cisternae); saclike bulges where it abuts t tubules |
| Excitation-Contraction Coupling (2) |  traveling down of action potential causes t tubule voltage sensitive protein to change shape; opens a calcium release channel in SR allowing calcium ions to flee sarcplasm; this rapid influx of calcium triggers contraction of muscle fibers |
| Excitation-Contraction Coupling (3) |  calcium binds to tropinin and removes the blocking action of tropomyosin; when Ca2+ binds, troponin changes shape, exposing binding sites for myosin on the thin filaments |
| Excitation-Contraction Coupling (4) | contraction begins; myosin binding to actin forms cross bridges and contraction begins; at this point E-C coupling is over |
| Role of Calcium (Ca2+) in Contraction | At low intracellular Ca2+ concentration: (Tropomyosin blocks the active sites on actin) (Myosin heads cannot attach to actin) (Muscle fiber relaxes) At higher intracellular Ca2+ concentrations: [Ca2+ binds to troponin ] [Troponin changes shape and moves tropomyosin away from active sites] [Events of the cross bridge cycle occur] [When nervous stimulation ceases, Ca2+ is pumped back into the SR and contraction ends] |
| Sacromere |  Functional unit of contraction in skeletal muscle fiber; Shorten when myosin heads in thick myofilaments form cross bridges with actin molecules in thin myofilaments |
| Formation of Cross Bridge | Initaited when calcium ions released from SR bind to troponin (This causes tropinin to change shape); Tropomyosin moves away from myosin binding sites on actin allowing myosin head to bind actin and form a cross bridge; Myosin head has to be activated before a cross bridge cycle can begin; ATP combines with myosin head and is hydrolized to ADP and inorganic phosphate (Energy from hydrolozied Atp activates myosin head forcing It to be in cocked position) |
| Cross Bridge Cycle: Step 1 |  cross bridge formation:Activated myosin head binds to actin forming a cross bridge; Inorganic phospahte released; Bond between myosin and actin becomes stronger |
| Cross Bridge Cycle: Step 2 |  the power stroke: ADP released and activated myosin head pivotes; Slides thin myofilament toward center of sarcomere |
| Cross Bridge Cycle: Step 3 |  cross bridge detachment: Link between mysoin head and actin weakens when another ATP ataches to myosin head; Myosin head detaches |
| Cross Bridge Cycle: Step 4 |  reactivation of myosin head: ATP hydrolized to ADP and inorganic phospahte; Energy released during hydrolizes reactivates myosin head returning it to cocked postion |
| Muscle Tension | the force exerted by a containing muscle on an object |
| Load | the opposing force exerted on the muscle by the weight of the object to be moved |
| Isometric | if muscle tension develops but the load is not moved; increasing muscle tension is measured |
| Isotonic | if the muscle tension developed overcomes the load and muscle shortening occurs; amount of muscle shortening is measured |
| Motor Unit | the nerve-muscle functional unit; consists of a motor neuron and all the muscle fibers it supplies; small motor units (more precise movement) [ex: fingers], larger motor units (less precise movement) [ex: hip muscles, bone] |
| Motor Nerve | served each muscle; each motor nerve contains axons of up to hundreds of motor neurons |
| Myogram | a graphic recording of contractile activity; line recording activity is called tracing |
| Muscle Twitch | response of a motor neuron to a single action potential of its motor neuron |
| Latent Period | the first few milliseconds following stimulation when excitation-contraction coupling is occuring; during this period, muscle tension is beggining to increase |
| Period of Contraction | cross bridges are active, from the onset to the peak of tension development, and the myogram tracing rises to a peak |
| Period of Relaxation | final phase, lasting 10-100ms, is initiated by reentry of Ca2+ into the SR; muscle tension decreases to zero and tracing returns to baseline |
| Graded Muscle Responses | muscle contraction can be graded in two ways: (1) by changing the frequency of stimulation and (2) by changing the strength of stimulation |
| Temporal/Wave Summation | if two identical stimuli (electrical shocks or nerve impulses) are delivered to muscle in rapid succession, the second twitch will be stronger then the first; temoral or wave summation is this second twitch; this occurs because second contraction occurs before the muscle has completely relaxed; primary function is to produce smooth continous muscle cells |
| Unfused or Incomplete Tetanus | if the stimulus strength is held canstant and the muscle is stimulated at an increasingly faster rate, the relaxation time between the twitches become shorter and shorter, the concentration of Ca2+ in the cytosol higher and higher, and the degree of wave sumation greater and greater, progressing to a sustained but quivering contraction |
| Fused or Complete Tetanus | as the stimulation frequency continues to increase, muscle tension increases until a maximal tension is reached; at this point all evidence of muscle relaxation dissapears and the contractions fuse into a smooth, sustained contraction plateau |
| Recruitment (Multiple Motor Unit Summation) | controls force of contraction; achieved by delivering shocks of increasing voltage to the muscle, calling more and more muscle fibers to play |
| Subthreshold Stimulus | stimuli that produce no observable contractions |
| Threshold Stimulus | the stimulus at which the first observable contraction occurs |
| Maximal Stimulus | the strongest stimulus that produces increased contractile force; represent the point at which all the muscles motor units are recruited |
| Muscle Tone | relaxed muscles that are almost slightly contracted; its due to spinal reflexes that activate first one group of motor units then another in response to activation of stretch receptors in muscles |
| Isotonic Contractions | muscle length changes and moves the load, the tension remains relatively constant through the rest of the contractile period; come in two flavors concentric and eccentric |
| Concentric Contractions | those in which the muscle shortens and does work, such as picking up a book or kicking a ball; |
| Eccentric Contractions | the muscle generates force as it lengthens; are important for coordination and purposeful movements; occur in calf muscle for example; 50% more forceful then concentric |
| Isometric Contractions | tension may build to the muscles peak tension producing capacity, but the muscle neither shortens nor lengthens; occur when a muscle attempts to move a load that is greater then the force (tension) the muscle is able to develop |
| Direct Phosphorylation |  ATP producing way; Metabolic Pathway; chemical reaction where CP (creatine phosphate) and ADP are used. Phosphate from CP is taken and put into ADP and turns to ATP; 1 to 1 ration; energy last for less then 10 seconds; does not require Oxygen;first stage body goes to to make energy; occurs in cytoplasm of cell |
| Anearobic Pathway (Glycolosis) |  metabolic pathway without oxygen; produced 4 ATP; 10 step process; every step is a chemical reaction and changes everytime (10 times); 1st 5 steps are known as energy investment phase (they require energy) [2 ATPS to produce these 5 steps]; 2nd Stages known as Reinvestment stage; makes only 2 ATPs; this process occurs in cytoplasm of cell; 2 energy sources glucose and glycogen; makes 2 or 3 ATP + 2 Pyruvic acids |
| Glucose Anearobic Pathway | yields 2 ATPs; does not require oxygen; also yeilds 2 pyruvic acids |
| Glycogen Anearobic Pathway | used when their is not enought glucose; stored fat; Yields 3 ATPs because it has allready been partially hydrated; also yields 2 pyruvic acids |
| Lactic Acid | made if their is no oxygen present or work is more then you can breathe; pyruvic acid is transformed to lactic acid; made either way by glucose or glycogen; liver can use or send back to be formed to pyruvic |
| Aerobic Pathway |  yields the most ATP with Oxygen; needs pyruvic acid to be shuttled from mitochondria (it is shuttled from Anearobic Pathway when 2 ATP and 2 Pyruvic acids); Pyruvic acid is transformed to Acetylcoa (happens in cytoplasm of cell); Krebs cycle produces 32 ATP |
| Aerobic Endurance | the length of time a muscle can continue to contract using aerobic pathways |
| Anaerobic Threshold | the point at which muscle metabolism converts to anaerobic glycolysis |
| Muscle Fatigue | the state of physiological inability to contract even though the muscle still may be receiving stimuli; due to a problem in excitation-contraction coupling or, in rare cases, problems at the neuromuscular junction |
| Contractures | lack in ATP; states of continuous contraction because the cross bridges are unable to detach |
| Oxygen Deficit | the extra amount of oxygen that the body must take in for these restorative processes |
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