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Muscle Phisiology
| Question | Answer |
|---|---|
| List the 3 types of muscle tissues | Skeletal, Cardiac and Smooth. |
| What is the function of skeletal muscle | Most skeletal muscles are attached to bones of the skeleton enabling them to control body movement. Striated |
| What is the function of Cardiac muscle | Found only in the heart. It moves blood through the circulatory system. Striated |
| What is the funtion of Smooth muscle | Primary muscle of internal organs and tubes; ie: stomach, bladder and blood vessels. Fxn: To influence the movement of material into, out of, and within the body. |
| Describe the basic organization of skeletal muscle tissue, skeletal muscle cells, and the sarcomere contractile units within them. | A collection of muscle cells, or muscle fibers. Each muscle fiber is a collection of cylindrical cell with serveral 100 nuclei on the surface of the fiber. They are the largest cells in the body, created by the fushion of many embryonic muscle cells. |
| Describe the myofilaments that compose the myofibrils in skeletal muscle fibers. | 1 MF has a 1000 myfibrils that occupy most intracellular volume, lil space for cytosol & organelles. MyoF made of proteins. Contractile Proteins: Myosin and AnctinRegulatory Proteins: Tropomyosin & troponinGiant Accessory Proteins: Titin & Nebulin |
| Thick filaments | Created by 250 joined Myosin molecules. A myosin molecule is composed of protein chains that intertwine to form a long tail and pair of tadpole like heads. |
| Thin Filaments | Made up of Actin in the MF. 1 Actin molecule is a globular protein (G-actin) they polymerize to form long chains called F-actin. 2 F-actin polymers twist together like double strands of beads create the myfibril. |
| Explain the 4 phases of skeletal muscle contraction and relaxation. | Excitation: Produce and electrical impulse.Excitation-Contraction coupling: The sequence of action potentials and Calcium felease that initiate contraction.Contraction: Process by which a muscle creates forceRelaxation: |
| -Molecular basis of contraction. | 1. Rigor state2. ATP Binds and myosin detaches3. ATP hydolysis4. Myosin reattaches: weak binding5. Pi release and the power stroke6. Release of ADP |
| -1. The rigor state | Myosin heads create crossbridges by tightly binding to G-actin molecules. In this state, no nucleotide (ATP or ADP) occupies the 2nd binding site on the myosin head. In living muscle, the rigor stae occurs for only a very brief period. |
| -2. APT binds and myosin detaches | An ATP molecule binds to the myossin head. This changes the actin-binding affinity of myosin, and the head releases from the G-actin molecule. |
| -3. ATP hydrolysis | The ATP-binding site on the myosin head closes around ATP and hydrolyzes it to ADP and inorganic phosphate (Pi). Both products remain bound to the head. |
| -4.Myosin reattaches: weak binding | Energy released from ATP causes th myosin head to swing &bind weakly to new G-actin mol,1or2 positions away from the G-actin to which previously bound.myosin has potential enery,& ready to move the actin filament past it. ADP and Pi still bound to myosin. |
| -5. Pi release and the power strokePi release and the power stroke (crossbridge tilting) | Power stroke begins when Pi released from its myosin binding site. Myosin head swings toward the M line,pushes attached actin filament in same direction. Aka CT b/c myosin head & hinge tilt from 90 angle relative to thick & Thin filaments to a 45 angle. |
| -Release of ADP (Last step) | Myosin releases ADP, The 2nd product of ATP hydolysis. At this point, the myosin head is again tightly bound to actin in the rigor state. The cycle is ready to begin again when a new ATP binds to myosin. |
| -What is muscle fatigue? | Muscle no longer able to generate or sustain the expected power output. Influence by the intensity and duration of the contractile activity, by whether the MF using aerobic or anaerobic metabolism, by the composition of the muscle,fitness level of person |
| What are some of the possible causes of muscle fatigue? | Muscle fatigue arises from excitation-contraction failure in the MF rather that from failure of control neurons or neuromuscular transmission. |
| Describe the 3 types of skeletal muscle fibers and their characteristics. | Slow-twitch fibers (ST), Fast-twitch oxidative-glycolytic fibers (FOG), Fast-twitch glycolytic fibers (FG) |
| Slow-Twitch Oxidative; Red muscle, Dark red myoglobin (ST) | Slowest speed of development of max tension.Slow myosin ATPase activity,SmLongest contraction duration.Moderate calcium ATPase activity in SR. Many MitoFatigue resistant endurance,Most used: posture,Oxidative; aerobic; metabolism, High Capillary |
| Fast-twitch oxidative-glycolytic: Red Muscle(FOG) | Mid speed of development of max tensionFast Myosin ATPase activityMedium-dShort con't durationHigh Ca2+ATPase act. in SR Mid.MitochFatigue resistant enduranceUse: Standing, walkingGlycotic,but more ox with end.train.metabMed.Cap density |
| Fast_twitch Glycolytic; White muscle, Pale(FG) | Speed of dev.of max ten: fastestMyosin ATPase act.: FAstd: LrgCon't dur: ShortCa2+ATPase act SR: High,few mitochEnd: Easy fatigueuse: Lease used: jumpingMetab: Glycol; more anaer than FOGCap den: low |
| What is a motor unit? | The basic unit of contraction in an intact skeletal muscle. Composed of a group of muscle fibers that fxn together and the somatice motor newuron that controls them. When the somatic motor neuron fires and action potential, all muscle fibers contract. |
| How do the motor units in fingers and eyes differ from those of larger, more powerful muscles? | Muscles used for fine motor actions contain only 3-5 MF. If one is activated only a few fibers contract. Big motor actions each motor unit contain 100's or 1000's of MF. |
| How is the length of the sarcomeres related to the strength of muscle contraction? | Sliding Filament Theory: As contraction occurs, the sarcomere shortens. |
| What are the other two methods whereby the contraction strength of muscle twitches can be increased? | Isotonic and Isometric contranctions |
| What is meant by treppe? | If a skeletal muscle is stimulated a second time immediately after the relaxation phase has ended, the contraction that occurs will develop a slightly higher maximum tension than did the contraction after the first stimulation. |
| Complete tetanus? | increasing the stim/rate until the relax phase is elim. During ct, AP's arrive so fast that SR doesnt have time to reclaim the Ca2+. The high Ca2+ [] in cytoplasm prolongs the cont state, making it continuous.norm muscular cont involve ct of the part. MF. |
| Incomplete tetanus? | If the stimulation continues and the muscle is never allowed to relax completely, tension will rise to a peak. A muscle producing peak tension during rapid cycles of contraction and relaxation is in incomplete tetanus. |
| Temporal summation? | Summation of two stimuli that follow one another in time. |
| Isometric (static) muscle contraction. | Contractions that create force without moving a load. Muscle has not shortened. sarcomeres shorten, generating force, but elastic elements stretch, allowing muscle length to remain the same. |
| Isotonic muscle contraction. | Sarcomeres shorten more, but b/c elastic elements are already stretched, the entire muscle must shorten. |
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lavy1318
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