Term
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Definition
| also called titin is a "cablelike" protein that extends from the Z discs to the M line through the core of each thick filament. It stabilizes the position of the thick filament and maintains thick filament alignment within a sarcomere. |
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Term
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Definition
| appears to be an actin-binding protein that is part of the I band of the sarcomere. |
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Term
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Definition
| is part of a protein complex that anchors myofibrils that are adjacent to the sarcolemma to proteins in the sarcolemma. |
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Term
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Definition
| A reddish, globular protein that is somewhat similar to hemoglobin. |
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Term
| synaptic knob of a motor neuron |
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Definition
| is an expanded tip of an axon. |
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Term
| Where the axon nears the sarcolemma of a muscle fiber, the synaptic knob .... |
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Definition
| enlarges and flattens to cover relatively large surface area of the sarcolemma. |
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Term
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Definition
| a specialized region of the sarcolemma of a muscle fiber |
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Term
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Definition
| has numerous folds and indentations (junction folds) to increase the membrane surface area covered by the synaptic knob. |
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Term
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Definition
| is an extremely narrow (20 nanometers), fluid-filled space separating the synaptic knob and the motor end plate. |
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Term
| The enzyme acetylcholinesterase (AChE): |
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Definition
| resides within the synaptic cleft and quickly breaks down ACh molecules following their release into the synaptic cleft |
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Term
| The first physiologic event of skeletal muscle contraction is muscle fiber excitation by a motor neuron- |
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Definition
| an event that occurs at the neuromuscular junction and results in release of ACh and its subsequent binding to ACh receptors |
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Term
| calcium entry at synaptic knob: |
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Definition
| A nerve signal is propagated down a motor axon. The nerve signal triggers the opening of voltage-gated Ca2+ channels within the synaptic knob. Calcium moves down its concentration gradient from the interstitial fluid through the open channels into the synaptic knob. Calcium binds with membrane proteins (synaptotagmin) exposed on the external surface of synaptic vesicles. |
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Term
| Release of ACh from Synaptic knob: |
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Definition
| The binding of calcium to synaptic vesicles triggers the merging of synaptic vesicles with the synaptic knob plasma membrane resulting in exocytosis of ACh into the synaptic cleft. Approximately 300 vesicles are released per nerve signal. |
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Term
| Binding of ACh at motor end plate: |
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Definition
| ACh diffuses across the fluid-filled synaptic cleft to bind with ACh receptors within the motor end plate. This causes excitation of a muscle fiber. |
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Term
Calcium Binding:
-calcium released from the sacroplasmic reticulum binds to ..... |
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Definition
| a subunit of globular troponin |
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Term
| globular troponin is a component of .... |
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Definition
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Term
Crossbridge cycling
1) crossbridge formation: |
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Definition
| myosin heads, which are in the "cooked," or ready, position attach to exposed myosin binding sites of actin. Binding of each myosin head results in formation of a crossbridge between the thick and thin filament. |
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Term
| If Calcium is still present, and the myosin binding sites are still exposed, then these four steps involving the myosin heads continue: |
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Definition
attach, pull, release, and reset.
It is the repetitive action of these steps that result in sacromere shortening, and a sacromere moves from its relaxed state into a contracted state. |
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Term
| The following changes to the sacromere occur in the contracted muscle: |
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Definition
| The H zone disappears, the I band narrows in width and many disappear, and the Z discs in one sarcomere move closer together. |
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Term
| Skeletal Muscle Relaxation |
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Definition
- The first event in muscle relaxation is the termination of the nerve signal in the motor neuron.
- this prevents further release of ACh.
- The ACh receptor closes
- Voltage-gated Calcium channels in the sarcoplasmic reticulum close.
- Troponin returns to its original shape when calcium calcium is removed and simultaneously the tropomyosin moves over the myosin binding sites on actin.
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Term
| The immediate supply of ATP is generated by the ... |
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Definition
| phosphagen system, which uses moecules that contain a high-energy phosphate |
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Term
| The phosphagen system is not ... |
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Definition
| dependent upon the presence of oxygen - that is, the processes of this system are anaerobic |
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Term
| an additional few seconds of energy in muscle is generated when the... |
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Definition
| enzyme myokinase transfers a phosphate from one adenosine diphosphate (ADP) to another ADP, yielding ATP and adenosine monophosphate (AMP). |
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Term
| One means of supplying ATP that occurs only in muscle tissue involves .... |
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Definition
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Term
| ATP is generated when the... |
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Definition
| enzyme creatine kinase transfers Pi from creatine phosphate to ADP, yielding creatine and ATP. |
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Term
| The short-term supply for ATP is provided by... |
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Definition
| anaerobic cellular respiration (glycolysis), a process that occurs in the cytosol and does not require oxygen. |
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Term
| Glucose is made available either directly from .... |
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Definition
| glycogen stores in the muscle fiber or delivered by the blood. |
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Term
| Lactic acid that enters the blood can then either... |
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Definition
| be taken up by the heart to be used as fuel to generate ATP or is taken up by the liver to produce glucose by gluconeogenesis |
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Term
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Definition
| amount of additional oxygen that must be inhaled following exercise to restore pre-exercise conditions |
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Term
| The additional oxygen is required primarly to: |
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Definition
- replace oxygen on hemoglobin molecules in the blood and myoglobin molecules in muscle.
- replenish glycogen stored in muscle fibers
- replenish ATP and creatine phosphate in the phosphagen system
- convert lactic acid back to glucose, a process that occurs when lactic acid is delivered by the blood to the liver.
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Term
| Power is related to the... |
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Definition
| diameter of a muscle fiber; large muscle fibers are more densely packed with myofibrils and produce a more powerful contraction. |
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Term
| Slow oxidative (SO) fibers: |
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Definition
| called type I, typically have half the diameter of other skeletal muscle fibers and contain slow ATPase. These cells produce contractions that are slower and less powerful. |
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Term
| SO fibers can contract over long periods of time without fatigue ATP because is |
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Definition
| supplied primarily through aerobic cellular respiration. |
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Term
| SO fibers appear dark because of the... |
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Definition
| presence of large amounts of myoglobin |
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