Term
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Definition
| The formation of skeletal muscle |
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Term
| When in development does myogenesis occur? |
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Definition
Early in the embryo and continues throughout fetal development
(This means that the number of myofibers are fixed at birth!!! Postnatally, satellite cells may contribute to increased fiber number but growth is mostly hypertrophic) |
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Term
| Transcription factors that regulate muscle cell differentiation and muscle formation |
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Definition
Myogenic regulatory factors (MRF)
Several different MRFs act in (sometimes overlapping) series |
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Term
| Role of progenitor cells? |
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Definition
| These cells are destined for muscle fate. They undergo the process of myogenesis. |
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Term
| What is meant by the biphasic formation of myotubules? (Explain details about first and second waves) |
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Definition
Biphasic formation of myotubules is broken into two waves:
First wave: primary, embryonic myotubes
Second wave: secondary, fetal myotubes
The second wave clusters around the primary myotubes, using them as a scaffold.
Think of it as paper machete dinosaur eggs (first thing to come to mind lol). Before dipping ripped newspaper in glue water to make the "egg," you gotta have some kind of base-- the small balloon. You use the small balloon as a scaffold to put the glue paper all over. When the glue paper dries, you have a dinosaur egg. This is what is happening with myotubes- the fist wave makes the balloon, the second wave is the glue paper, placing themselves around the balloon |
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Term
| Steps from determination to maturity of myofibers (5) |
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Definition
Determination of mesodermal stem cells
Commitment, proliferation of presumptive myoblasts
Myoblasts line up and terminal withdraw from cell cycle
Myotubes differentiate and diffuse
Myfibers mature and grow via hypertrophy |
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Term
| What are the different names of the muscle cells starting with myogenic progenitor cells to mature myofibers? |
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Definition
Myogenic progenitors
Myoblasts
Myotubes
Myocytes/myofibers |
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Term
| Three different types of muscle |
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Definition
Skeletal muscle
Smooth muscle
Cardiac muscle |
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Term
| Characteristics of skeletal muscle |
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Definition
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Term
| Characteristic of cardiac muscle |
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Definition
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Term
| Characteristic of smooth muscle |
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Definition
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Term
| Connective tissues present in muscles are |
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Definition
tendons and layers around the various structures, such as:
epimysium, perimysium, endomysium |
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Term
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Definition
| surrounds the entire muscle |
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Term
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Definition
| surrounds bundle of muscle fibers (fascicles) |
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Term
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Definition
| surrounds individual muscle fibers |
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Term
| skeletal muscle organization (quick and dirty) |
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Definition
| Muscle -> muscle fiber bundle -> muscle fiber/muscle cell -> myofibril -> myofilament |
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Term
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Definition
| plasma membrane of muscle cell |
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Term
| what structures does the sarcolemma have and why are they important |
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Definition
Transverse tubules (T-tubules)
these are the little invaginations (think like if you take an exam glove off, the finger holes are turned inside out and the fingers go deeper/past than the rest of the glove. Think of these as invaginations and the rest of the glove as the sarcolemma)
They are important bc the t-tubules are able to have close contact with the myofibrils. On a deeper level, the T-tubules form the Triad w/ the sarcoplasmic reticulum. Action potentials travel down the T-tubules |
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Term
| Why is the sarcoplasmic reticulum important? |
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Definition
it stores calcium and is part of the terminal cisternae. This is important for contraction of muscle.
It is equivalent to the endoplasmic reticulum. |
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Term
| As far as nucleated cells go, how are myofibers different? |
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Definition
| Myofibers are multinucleated. Remember how the myotubes fused together- the result is multinucleated cells. |
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Term
| What are the two myofilaments? |
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Definition
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Term
| Of the two myofilaments, which is the thin and which is the thick filament? |
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Definition
Actin is the thin filament while myosin is the thick filament.
I remember this as ACTin is ACTive, therefore is thinner than myosin. |
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Term
| What are the contractile elements of the myofiber? |
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Definition
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Term
| What is the functional division of the myofibril? |
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Definition
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Term
| What are the spatial divisions of the myofibril |
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Definition
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Term
| What is the functional unit of contraction? |
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Definition
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Term
| Which myofilament is anchored on the Z-disc/Z-line? |
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Definition
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Term
| What mutated gene was found as the cause for Duchenne Muscular Dystrophy? What implications does this have for the cell? |
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Definition
Dystrophin
It is part of a protein complex, so it connects the cytoskeleton/myofibrils to extracellular matrix through the sarcolemma. It helps hold everything together. So if this doesn't work, theres not that piece that helps hold everything together during contractions and relaxations of the muscle |
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Term
| Which myofilament has the two heavy chains that wrap around each other? What does this form? |
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Definition
| Myosin has two heavy chains that wrap around each other forming the tail along with a globular head. |
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Term
| Why is the myosin head important? |
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Definition
| has ATPase activity and actin binding capacity. |
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Term
| Actin is not simply a chain of molecules by itself. What other molecules are with actin? |
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Definition
| Tropomyosin, Troponin T, Troponin I, Troponin C |
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Term
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Definition
| wrapped around actin-- it is covering the myosin binding site when calcium is not around. Gets pulled away when Tropomyosin C binds to calcium. |
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
| Tropomyosin T, C, and I make up what? |
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Definition
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Term
| What site is where the nerve meets muscle? |
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Definition
| Neural muscular junction. Motor end plate is a part of this, which is a bunch of receptors that receive the signals/action potentials from the axon terminal of motor neuron |
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Term
| What is on either side of the T tubule? |
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Definition
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Term
| Three major classifications of motor tasks are |
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Definition
Postural joint stabilization
Long lasting repetitive activities (respiration, locomotion)
Fast generally powerful actions (jumping, kicking) |
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Term
| Slow twitch muscle (Type 1) |
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Definition
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Term
| Fast twitch muscle (type 2) |
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Definition
| strength/ "fight or flight" |
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Term
| Fatiguability of slow oxidative fiber type |
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Definition
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Term
| Fatiguability of fast oxidative-glycolytic fiber type |
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Definition
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Term
| fatiguability of fast glycolytic fiber type |
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Definition
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Term
| Three methods of ATP regeneration |
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Definition
| Creatine phosphate, anaerobic glycolysis, glucose oxidation |
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Term
| Which type of ATP regeneration is efficient, giving 36 ATP per glucose, but is slow and requires constant O2 delivery? |
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Definition
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Term
| Which type of ATP regeneration is rapid, but has a limited reserve and requires no oxygen? |
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Definition
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Term
| Which type of ATP regeneration is rapid but inefficient and produces lactic acid? |
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Definition
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Term
| Slow twitch fiber vs fast twitch fiber? |
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Definition
Slow twitch: aerobic, steady power, endurance
Fast-twitch fiber: anaerobic, explosive power, easily fatigued |
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Term
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Definition
| made up of a motor neuron and the skeletal muscle fibers that its axonal terminals innervate. The fibers within a motor unit are the same fiber type. |
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Term
| When is the only significant period when muscle fiber number can be increased? What is this a result of? |
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Definition
| prenatally. a result of significant hyperplasia (hypertrophy is minor during this period) |
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Term
| The increase in muscle fiber number postnatally is attributed to what? |
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Definition
| lengthening of partial fibers |
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Term
| How do satellite cells affect the muscle fiber number? |
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Definition
They can be activated to proliferate and fuse with other satellite cells to form new fibers or fuse with existing fibers to provide myonucleus/nuclei.
Necessary to do work; if you continuously need to do more strenuous work involving muscle strength (like weight training), your body will adapt so that it is able to do this |
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Term
| What type of cells are small mononuclear progenitor cells w/ virtually no cytoplasm? |
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Definition
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Term
| Where are satellite cells located? |
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Definition
| between basal lamina and sarcolemma of muscle fiber |
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Term
| Differences in body size is related to what? Why? |
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Definition
| number of muscle fibers. It wouldn't be diameter because this is not favorable from a metabolic standpoint due to diffusion of nutrients- this is restricted if the diameter is excessive. |
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Term
| How can nutrition alter muscle fiber number? What implications could this cause? |
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Definition
Only during prenatal development. Postnatally, nutrition has little effect on muscle fiber number.
So, if a pregnant pig is starved, her litter will have a decreased number of muscle fibers. When they grow up, they have less muscle, since muscle fiber number only increases prenatally. They could reach the same postnatal weight, but this wouldn't be due to muscle mass as it would be with non-starved litters. |
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Term
| Males vs females in regards to muscle fiber number |
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Definition
| males have greater number of muscle fibers at birth than females (though there are species differences) |
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Term
| When does muscle fiber size increase dramatically in gestation? |
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Definition
| During the last third of gestation and continues into postnatal period |
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Term
| Two components of increased muscle fiber size postnatally |
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Definition
Radial growth: generation of newly synthesized myofibrils, not myofibers. The existing myofibrils split to form new myofibrils. Achieved through work or exercise
Longitudinal growth: related to stretch. Imposed by bone lengthening during skeletal growth- sarcomere addition to the end of myofibrils |
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Term
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Definition
| Males have larger muscle fiber cross sectional area. |
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Term
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Definition
| increased nutrition causes increase in muscle fiber size compared to restricted |
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Term
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Definition
| most observed with breeding stock and companion animals |
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Term
| What increases in muscle size by increasing myofiber size? |
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Definition
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Term
| Exogenous growth hormone effects include? |
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Definition
| Sex and muscle development |
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