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Muscle Part 2
| Question | Answer |
|---|---|
| What causes red muscle appear red? | It has more oxidative metabolism. It has more mitochondria that have a lot of heme-containg proteins that give a red color. Usually more vascular |
| Describe type 1 muscle type | Slow fibers. Highly oxidative fibers. Has a lot of mitochondria. |
| Describe type 2a muscle type | fast fibers and fast oxidative |
| Describe type 2x/2b muscle type | Used for maximum strength (fast glycolytic). Recruited occasionally |
| Where are satellite cells located? | Between the sarcolemma and basement membrane |
| Functions of satellite cells | Muscle growth and regeneration. Muscles grows by hypertrophy. |
| What triggers satellite cells? | Pain. Triggers proliferation cells and they add new myocnuclei that become peripherally located in pre-existent fibers. Satellite cells are released when muscle is damaged. |
| Describe Duchenne Muscular Dystrophy (X-linked) | Dystrophin is not expressed. Things can leak out and die. Regeneration occurs but nuclei are centrally located. Satellite cells are depleted and you get muscle wekaness. Diaphragm muscle gives out. |
| What are the conducting fibers of cardiac muscle? | Cardiac myocytes, NOT nerves |
| Where is the nuclei located in the cardiac fibers? | Centrally located (sometimes there are 2) |
| What constitutes a cardiac fiber? | Cells joined together that are coupled by electrical coupling produced by gap junctions which are part of intercalated discs |
| Describe specialized cardiac myocytes | Form the conducting system, have some striation and some myofibrils |
| What causes cardiac muscle beat? | It beats spontaneously. It does not need innervation to beat. Beating is coordinated by coupling of cells |
| What color is cardiac muscle? | Red, it has lots of mitochondria |
| What kind of junctions are in interculated discs? | Macula adherens, sheet-like fascia adherens where thin filaments insert, Gap junctions |
| Why are cardiac muscle referred to as functional syncytium? | They are electrically coupled even though they are single separate cells. |
| What is difference between cardiac muscle sliding filament and skeletal muscle? | Cardiac muscle's strength of contraction can be modulated by post-translation modification. Phosphorylation can affect the ATPase of myosin. (Some troponins) |
| Describe T-tubules of cardiac muscle | Very large in ventricles, smaller in atrium. No voltage sensor in T-tubules |
| What causes calcium to rise in cardiac muscle? | Depolarization signals SR to release calcium. There is a calcium channel functionally that releases calcium across the t-tubule membrane. Calcium-induced calcium release |
| What does the atrial have that is not found in ventricles? | Atrial granuales |
| Describe Atrial Natriuretic Factor (ANF) | Increased muscle activity can cause atrial vesicles to fuse with sarcolemma and release into blood. Travels to receptors and triggers release of factors that regulate blood pressue. |
| Are there satellite cells in the heart? | No. No regenerated muscle. If muscle is damaged it is replaced by fat and connective tissue |
| Describe the cells and nuclei of smooth muscle | The cells are spindle-shaped and have a single nuclei. Cells can be electrically coupled. It is innervated by parasympathetic/sympathetic |
| What do the thick, thin and intermediate filaments of smooth muscle contain? | Thick: Myosin, Thin: Actin, Intermediate: Desmin and Vimentin |
| What inserts into the dense body of smooth muscle? | Thin filaments |
| Where does calcium bind in smooth muscle? | Binds to Calmodulin. NO tropnin. There is a protein called Caldesmin that sits on thin filament can bind calcium. |
| What type of binding mechanism does smooth muscle use as opposed to striated muscle? | Myosin-linked mechanism as opposed to actin linked |
| Described the myosin-linked mechanism smooth muscle uses | When calcium rises it binds to calmodulin. Calmodulin-calicium complex activates a myosin-light chain kinase. Tail of myosin blocks actin binding site and phosphorylation causes tail to expose it. |
| What triggers calcium binding proteins to be released into cytosol in smooth muscle? | Depolarization or direct signaling at times |
| Describe Artherosclerosis | In smooth muscles in walls of the arteries it can udergo excessive growth which cause closing off of the lumen of the blood vessel |
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