Term
| What are the 3 types of muscle |
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Definition
1. Skeletal
2. Cardiac
3. Smooth |
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Term
| Describe the cell structure of skeletal muscle and the activities they are build for |
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Definition
Cell Setup: Long cells, multinucleated with nuclei on the peripheral of the cells
Activity: Smooth, quick, discontinuous, voluntary contraction |
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Term
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Definition
| Muscle cells are muscle fibers |
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Term
| Describe the setup of thick filaments |
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Definition
| Rod shaped, bipolar consisting of a bare zone in the middle and 2 ends (a myosin head and a myosin tail) that are lined with myosin |
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Term
| Describe the setup of myosin |
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Definition
| globular heads attached to a rod where the head acts as the actin binding site as well as an ATPase (2 globular heads in myosin 2, which is the type that interacts in muscle cells) |
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Term
| Describe the polarity and location of thin filaments and how they interact with thick filaments in muscle contraction |
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Definition
Polarity: Barbed plus head with a pointed minus end
Location: Plus end is located at the Z line with the minus end in the middle of the A band
Interaction: Myosin motor heads on the ends of thick filaments move from the minus to the plus end of thin filaments |
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Term
| What is tropomyosin and what role does it serve on muscle fibers? |
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Definition
| A rod like structure coiled around F-actin that serves as the binding site for Troponins |
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Term
| What are the 3 Troponins and what role do they do? |
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Definition
TN-I: Binds to F-actin to inhibit actin-myosin interaction
TN-C: Removes TN-I's inhibition in the presence of high [Ca]
TN-T: Tethers the other 2 to tropomyosin
(I: Inhibits T: Tethers C: Calcium) |
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Term
| What is the energy source for the sliding mechanism of muscle contraction? |
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Definition
ATP hydrolysis driven by conformational changes to the myosin heads as they slide
Note: Also driven by high [Ca] to activate TN-C |
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Term
| What are the two major ways [Ca] regulates actin-myosin interaction? |
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Definition
1. Actin-based regulation (thin filament)
2. Myosin-based regulation (thick filament) |
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Term
| Describe the mechanism of actin-based regulation |
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Definition
Calcium binds to TN-C it causes the troponin complex to move away from the myosin binding site permitting interaction
Note: Primarily found in striated muscle |
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Term
| Describe the process of myosin-based regulation |
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Definition
1. Calcium binds to calmodulin
2. Calmodulin/calcium complex activates the kinase MLCK
3. activated MLCK facilitates phosphoylation light chain proteins to activate them for use (paired with ATP hydrolysis for energy) |
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Term
| What parts of the sarcomere does Titin span and what does it accomplish in the A band and I band |
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Definition
1. Titin spans from the M-line to the Z-line
2. In the A-band titin helps form the A-band
3. In the I-band Titin provides and elastic restoring force to maintain resting length |
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Term
| What are the 2 isoforms of Titin and what role do they play in heart failure? |
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Definition
1. NB2 and NB2A
2. NB2 is stiffer, so increased presence of NB2A leads to a more compliant heart (NOT GOOD). Heart failure has been correlated with higher NB2A:NB2 ratios (usually 2 or higher) |
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Term
| Where are the 2 signaling centers of the muscle? |
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Definition
M-line and Z-line
Senses mechanical stress//deformation and modulates protein generation in response |
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Term
| What is excitation-contraction coupling? |
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Definition
| The linking of chemical and electrical signals at the cell surface to muscle contractions, done via the release of Calcium down T-tubules to the sarcoplasmic reticulum |
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Term
| What role to T-tubules play in E-C coupling |
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Definition
| Most muscle cells are large so passive diffusion of Calcium would take too long for an appropriate response, so action potentials are conducted into the body of the cell by T-tubules |
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Term
| What role to sarcoplasmic reticulum play in muscle contraction? |
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Definition
| They are linked to T-tubules and serve as the storage and release depots of calcium in the cell body |
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Term
| What role do intermediate filaments play in muscle contraction and what particular type of IF is present predominantly in muscle cells? |
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Definition
1. IFs form a 3D lattice that mechanically couples the myofibrils to the organelles of the cell. They are necessary for the maintenance but not assembly of myofibril (lack of IFs does not stop myofibril formation, but will cause them to break down after extended use).
2. Muscle IFs are largely composed of Desmin. |
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Term
| Describe the appearance of cardiac muscle cells |
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Definition
| Short, with centrally placed nuclei, with 1-2 nuclei per cell, with intercalated disks and electrical linkages (gap junctions) that allow multiple cells to behave as a single unit in contractions |
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Term
| What are cardiomyopathies and what is their most common cause? |
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Definition
Heart muscle diseases that are associated with the mechanical and electrical dysfunction of the heart.
They are caused most frequently by mutations in genes that code for sarcomere proteins |
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Term
| What is the appearance of smooth muscle? |
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Definition
| Small, spindle shaped, with a single, centrally placed nucleus, tightly packed cells with no striations |
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