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Muscle Part 1
Muscle part 1
| Question | Answer |
|---|---|
| What control is skeletal muscle under? Striated? | voluntary control by CNS. Yes |
| What are the principal cells of skeletal muscle? | Large multinucleated syncytium |
| What constitutes a myofiber? | Small myoblasts that fuse together to form a tube that matures |
| What is each cell lined with? | A basement membrane and endomysium |
| What is a fasicle? What is it enclosed by? | A bundle of fibers enclosed by perimysium |
| How are fasciles held together? | By Epimysium |
| Where is the nuclei located in skeletal muscle? | At the periphery |
| In muscle disease where do the nuclei end up? | In the interior of the fiber |
| What is the plasma membrane referred to? | Sarcolemma |
| Each fiber is innervated by how many nerves? | A single nerve for each fiber |
| What makes up a motor unit? | A single nerve that branches off and one nerve will innervate a set of fibers |
| When is recruitment of motor units important? | When you are using all of your strength |
| What are myofibrils? | Contractile organells that are embedded in the cyoplasm and ends of fibers |
| When are myofibrils triggered to shorten? | when the cells are activated my a nerve |
| What is the sarcoplasmic reticulum? | internal membranes. It surrounds each myofibril which is important in the activation mechanism |
| Why are most of the ribosomes free in skeletal muscle? | Because they are not making a lot of proteins for export but for internal use |
| What makes up a sarcomere? | From one Z line to another Z line |
| What forms an A band in the sarcomere? | Thick myofilaments |
| What do the thick myofilaments contain? | Myosin which has 2 globular heads and 2 helical tail regions that wrap around each other |
| What does the globular head of myosin conatin? | Myosin light chains:Noncovalently sit on globular heads(conatin ATPase. Also actin binding sites. |
| What type of process does myosin assemble? | By a bipolar process |
| Describe thin filaments and components | Formed by actin. A double helix (that can't be separated). Tropomyosin sits on groove of helix and troponin sits on tropomyosin. |
| What do thin filaments insert into? | Into the Z line |
| What interconnects the Z lines? | Intermediate filaments that resist pulling |
| What proteins are Z lines comprised of? | Alpha-actin and desmin(glue function) |
| Describe the titan protein and its functions | Extends from the Z-lines along thin filaments and touches thick filaments. It is a molecular spring to sense tension. It can bind to transcription factors important in protein degradation inf the mulscle. It can translate tension into growth stimulation |
| What does cross bridges refer to? | The crossing of thin and thick filaments. The overlap changes |
| What is riggermortus? | Stiffening of the muscle due to death of a cell |
| How is cross-bridges regulated? | Tropomyosin-Troponin position that blocks myosin from binding to actin. When a muscle is activated calcium is relased and binds to the troponin C-subunit which causes a rotation of tropomyosin-troponin and exposes the myosin-binding site on actin |
| What causes calcium to rise? | Depolarization. T-tubules have voltage sensor which triggers change in calcium channel. Calcium is released through ryanodine channel and goes to cytosol to bind to troponin |
| What can anesthetics trigger and how is it treated? | Excessive, uncontrolled release of calcium through ryanodine channel and cause muscles to heat up and super contract. Dantrolene blocks calcium channel. |
| What is a muscle spindle? where is it found? | Encapsulated structure in usually perimysium. It functions in proprioception, sensing muscle tension to feed back to CNS for regulation |