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NPB 101
Lecture 10
| Question | Answer |
|---|---|
| What is the definition of a muscle? | The ability to shorten when stimulated, and to be able to exert force in the direction of shortening. |
| What is the common material that bone, tendon, and muscle are all made out of? How is it used in these body parts? | Collagen. Bone: Ca phosphate crystals are deposited on collagen to harden it Tendon: polymerized collagen Muscle: Muscle cells surrounded by collagen sheaths |
| What happens when a muscle extends? | The other muscle must relax so that there can be movement. The flexor relaxes and gets shorter while the extensor gets longer and flexes |
| As you get smaller and smaller what are the different components of the muscle? | Muscle, muscle fiber, myofibril, sarcomere |
| Do motoneurons generate EPSP's, IPSP's, or both to the muscles? What does this mean for the muscle? | Only EPSP's. This means that the muscle can't relax on its own. It can only stop receiving an EPSP, then be stretch back to its original state by another muscle. |
| What are the four different zones in the sarcomere? | The H zone: only thick filament, the I zone: Only thin filament, the A band: Both thick and thin filament overlapping, and the Z line: the middle of each I band |
| What are the thin and thick filaments made out of? | Thin: Actin, Thick; Myosin |
| What happens in the sarcomere during contraction? | It shortens because the thick and thin filaments overlap more with one another |
| What triggers a contraction? | A motoneuron releases acetylcholine and elicits an EPSP |
| What is a neuromuscular junction? | The point where the motoneuron connects to the muscle fiber. There is at least one connection on every fiber |
| How does the motoneuron elicit at response in the muscle? | Just like in the brain, the signal goes down the axon, the axon terminals get depolarized, this lets out a neurotransmitter which then depolarizes the muscle by allowing Na into the cell |
| How does the depolarization spread to the muscle fibers that are below the surface? | The depolarized signal then flows down the T-tubule and into the Sarcoplastic reticulum |
| Where are the acetylcholene receptors? | On the surface of the terminal axon |
| How happens chemically when the axon depolarizes that leads to the muscle? | The depolarization travels down the T-tubule to the different muscle fibers. This signals the release of Ca in the SR, by signaling the Ryanodice receptor, which travels around the fluid in the myofibril. |
| How does the release of Ca trigger a muscle flex? | The myosin on the thick filament wants to attach to the actin on the thin filament but the topomyosin is in the way. The Ca block the topomyecin so the filaments can form a bridge. Then the thick filament pulls the thin filament by bending the bridge |
| How does the cross bridge return to its normal configuration? | By detaching from the thin filament then hydrolizing an ATP to an ADP |
| Why does the body stiffen during rigor mortis? | There is no ATP present to change the conformation of the cross bridge |
| What are the five components that control contraction strength? | Motor unit size, number and frequency of spikes, muscle length, fatigue, amount of thick and thin filament |
| What does it mean when the motor unit size is large? | It means several muscle fibers are connected to a single motoneuron so that the muscle strength is greater, however the control is lessened. |
| How do the number of spikes in the motoneuron control the contraction strength? | The spikes are cummulative. One spike is a twitch, several spikes is a larger movement. Multiple contiuous spikes results in the most contraction strength, this is called "tetnanus" |
| How does the correct muscle length control the contraction strength? | At the correct length, part of the filaments are overlapped, however, not fully so that they can still generate force. |
| How does fatigue affect muscle contraction strength? | If a muscle fatigues it cant generate force. Muscles that quickly fatigue often generate the most force. |
| Name the three kinds of muscle | Skeletal, cardiac, smooth |
| Which muscles are striated and which aren't? | The skeletal and cardiac are, the smooth isnt |
| What are the differences in the contractile process of each of the three kinds of muscles? | Skeletal muscles use the motoneurons to depolarize the muscle and generate tension. Cardiac and smooth muscles use gap junctions which means that if one cell contracts, they all do. |
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24rory
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