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62 Cards in this Set
- Front
- Back
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Skeletal muscle is highly what (meaning it has a good blood supply)?
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(vascularized) to supply the needed oxygen and nutrients, and to remove waste products.
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Skeletal muscle is innervated by what?
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motor neurons (somatic nervous system). A single axon will usually innervate several muscle fibers.
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What is a motor unit?
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A motor neuron and all the muscle fibers that it innervates.
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What is a neuromuscular Junction?
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The point of contact between the motor neuron and he muscle fibers. (ex: synapse)
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What are 7 microscopic parts of Skeletal muscle anatomy.
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Muscle fibers, Sarcolemma, Sarcoplasm, Myofibrils, Sarcoplasmic reticulum, Transverse Tubules, and the Sarcomere.
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What is a muscle fiber?
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aka "muscle cells", are a synctium which is a group of cells that fused to form one large structure, it has many nuclei.
-is surrounded by endomysium |
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What is the Sarcolemma?
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the plasma membrane that surrounds a muscle fiber.
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What is sarcoplasm?
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the cytoplasm of muscle fibers.
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What are the Myofibrils?
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-They are thread like filaments contained within a muscle fiber.
-the contractile element of muscles. -contains myofilaments. |
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What is the Sarcoplasmic Reticulum?
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It surrounds the myofibrils
It stores Calcium It contains calcium pumps that continually pump Ca++ from around the myofibrils back in to the sarcoplasmic reticulum. |
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What are the Transverse Tubules?
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-Move at right angles to the sarcoplasmic reticulum
-they are invaginations of the sarcolemma that pass signals to the sarcoplasmic reticulum. |
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What is the sarcomere?
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The functional unit of a myofibril.
- is made up of various myofilaments (proteins) |
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What are sarcomere myofilaments?
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-thick filaments (made from myosin)
-thin filiaments (mostly actin) -the titan (a think, elastic protein strand that stabilizes the thick filament) -Troponin and Tropomyosin- surround the binding sites on Actin |
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What are the regions of the sarcomere?
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The A band, The I band, The Z disc, The M line.
(M.Z.I.A. My Zebra Is Awesome) |
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What is the A band?
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The A band is the region that contains the thick filaments (Myosin) also known as the dark band.
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What is the I band?
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The region that does not contain the thick filaments (Myosin), also known as the light band.
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What is the Z disc?
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The Z disc is a layer of protein that separates the sarcomeres.
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What is the M line?
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The M line is the line of protein that runs down the middle of the sarcomere.
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Alternating the A and I bands produce what in skeletal muscle?
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The striated appearance.
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What are the 12 sequence of events associated with muscle contraction?
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1.) An action potential travels down the axon towards the neuromuscular Junction.
2.) The Action potential reaches the axon terminal and causes a synaptic vesicle to release neurotransmitter in to the synaptic cleft, via exocytosis. 3.)ACH (Acetylcholine) diffuses acros the synaptic cleft 4.) ACH binds to a receptor on the motor end plate (the portion of the neuromuscular unction that is on the muscle) 5.)Ach binding to the receptor produces an Action Potential which travels alon the T-tubules towards the sarcoplasmic reticulum. 6.) The action potential signals the sarcoplasmic reticulum to release calcium across the myofibrils. 7.) Calcium binds to Troponin. Tropomyosin is attached to Troponin. When calcium binds to Troponin the tropomyosin slides across the thin filament (Actin). This movement exposes the Myosin binding sites that are on the thin filaments. 8.) The myosin heads of the thick filament can now approximate the myosin binding sites. 9.) ATP attaches to the Myosin head. ATP is split into ADP and phosphate. This activates the myosin head. 10.) The activated Myosin head binds to the myosin binding site. The phosphate group is released. 11.) The myosin head flexes (Power stroke) which draws the thin filament towards the M line. AdP is released after the myosin head is flexed. 12.) The myosin head remains attached to the Myosin binding site until another ATP attaches to it. The myosin head is then released from the myosin binding site, and becomes extended. It will then bind to another myosin binding site. Steps 9, 10. 11 are repeated until the signal from the neuron ceases. |
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What is the synaptic vesicle?
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It is neurotransmitter enclosed in a lipid bilayer "packet"
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What is Acetylcholine ACH?
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Is the neurotransmitter for skeletal muscle contraction.
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What does ACH stand for?
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Acetylcholine
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What is the sliding filament mechanism?
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The process where the thin filaments are drawn towards the M line. This involves the repeating of steps 9-12 of muscle contraction.
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what is Acetylcholinesterase? How does it relate to the termination of muscle contraction?
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it is an enzyme that deactivates ACH, in the synaptic cleft continually breaks down ACH. If the signal to release ACh into the synaptic cleft ceases, the action potential in the muscle will cease.
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The break down of ACH is the first part of the termination of muscle contraction, what is the second?
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The calcium pumps in the sarcoplasmic reticule continuously pump the Ca++ around the myofibrils back into the sarcoplasmic reticulum. With no CA++ to bind to Troponin , the Tropomyosin slides over the myosin binding sites. The myosin head now has nowhere to bind, thus muscle contraction ceases.
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What is a reusable mineral that is not degraded by muscle contraction?
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Calcium.
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What is continually broken down into ADP, so it must continually be regenerated?
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ATP
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Where is creatine phosphate found?
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in the sarcoplasm
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what provides energy for maximum muscle contraction for approx. 15 seconds.
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Adp+ Creatine phosphate
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Where does anaerobic respiration occur?
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it occurs in the sarcoplasm, no oxygen is required.
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what provides energy for maximum muscle contraction for 30 to 40 seconds.
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anaerobic respiration
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When plenty of oxygen is available Pyruvic acid is transported where? Where what cycle occurs?
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pyruvic acid is transported to the mitochondria where the Krebs cycle occurs.
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When the muscle is short of oxygen, Pyruvic acid is converted to what kind of acid which will diffuse into the blood, as the ph of muscle decreases the ability of the muscle to function will also decrease.
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lactic acid.
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Aerobic respiration
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-occurs in the mitochondria
-requires oxygen (oxygen is the limiting factor) - produces up to 36 ATP -Can get energy from the breakdown of Pyruvic Acid, fatty acids and amino acids. -provide energy for prolonged muscle use. |
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Muscle fatigue
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The inability of a muscle to contract forcefully after prolonged activity.
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what is recovery oxygen consumption?
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the elevated use of oxygen after exercise to replace the lost energy stores and to facilitate tissue repair after exertion.
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What is motor unit recruitment?
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the process where an increasing number of motor units are activated in response to an increased load.
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What are the key factors in the control of muscle tension?
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a)the amount of stretch on the muscle fibers prior to contraction.
b.) Frequency of stimulation- The number of nerve impulses that pass through a motor unit per second. c.)the number of motor units that are stimulated. d.) the type of muscle fiber. |
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What is frequency of stimulation?
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The number of nerve impulses that pass through a motor unit per second
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What is wave summation?
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the increased strength of a muscle contraction that result when nerve impulses occur in rapid succession.
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What is motor unit recruitment?
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The process where an increasing number of motor unit are activated in response to an increased load.
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What is the refractory period?
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the period of time in which an excitable cell (ex: muscle or nerve cell) cannot respond to a stimulus. Different types of muscle fibers have different refractory periods.
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What is muscle tone?
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the tautness or tension that is constantly in a muscle due to involuntary, weak stimulation of the motor units.
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What is flaccid?
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The loss of muscle tone associated with damage to motor neurons.
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What are types of skeletal muscle fibers?
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1.) slow oxidative fibers.
2.) fast oxidative-glycolytic (dark meat) 3.) fast glycolytic fibers (white meat) |
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These skeletal fibers are a red fiber, with high myoglobin content, an iron containing protein that binds oxygen, they are the smallest skeletal fibers in diameter, they contain many mitochondria, these fibers contract slower than the other two fiber types, these fibers resist fatigue, they are found in postural muscles and in muscles involved in endurance (ex: prolonged contraction)
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slow oxidative fibers.
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These skeletal fibers are a red fiber, high in myolobin content, intermediate in diameter, contains many capillaries, generate atp by aerobic and anaerobic contraction, uses atp faster than slow oxidative fibers, provides faster muscle contraction but fatigue quicker than slow oxidative fibers, these are fibers associated with activities like walking and sprinting.
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Fast oxidative-glycolytic fibers (dark meat)
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These skeletal fibers are a white fiber with low myoglobin content, they have few capillaries, few mitochondria, generate most ATP via glycosis (anaerobically), they provide strong and rapid contraction, they fatigue the quickest and provide quick, short bursts of muscle contraction.
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Fast glycolytic fibers.
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Most skeletal muscles are a combination of what three skeletal muscle fibers?
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Slow oxidative fibers, fast oxidative-glycolytic fibers, and fast glycolytic fibers.The relative proportion of each fiber type depends on the type of activity that the muscle is used for.
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Cardiac Muscle
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contains actin and myosin filaments aranged in sarcomeres
-are striated -remains contracted longer than skeletal muscle -most of the atp is produced by aerobic respiration -can use lactic acid to form tap -cardiac muscle contraction is stimulated from within the heart (sinoatrial nod) vs motor units. -are under involuntary control -have intercalated discs and a centrally located nucleus. |
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What is the intercalated disk?
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a thickening of the sarcolemma between adjacent cardiac muscle cells, contains many desmosomes and gap junctions
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What type of muscle contains irregulary arranged thick and thin filaments?
has no striations, are spindle shaped (thicker in the middle, narrow at the ends), under involuntary control, the source of stimulation depends upon the location of the muscle, ex: local neurons, hormone, stretch, act, these also contract slowly and remain contracted for a prolonged period of time. |
smooth muscle
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What takes place in the regeneration of muscle tissue?
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most damaged muscle is replaced via fibrosis (scar tissue)
most undamaged cells will enlarge to attempt to make up for lost function -have limited regeneration |
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What are satellite cells?
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cells located in skeletal muscle tissue that can differentiate to become new muscle cells, not enough of these cells exist to replace damaged cells.
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What takes place in the regeneration of cardiac muscle?
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Cardiac muscle heals via fibrosis (scar tissue), existing cells can enlarge to provide additional contraction strength, recent studies have discovered stem cells that can differentiate to become healthy cardiac muscle cells, the extent of this regeneration remains to be discovered.
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What takes place in the regeneration of smooth muscle?
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Cells can enlarge to provide additional contraction strength
-certain smooth muscles retain the ability to undergo cell division (such as myometrium of the uterus) -limited regeneration capablility but much greater than skeletal muscle. |
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What are pericytes?
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stem cells located in capillaries and small veins.
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What are the effects of aging on the muscle cells?
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the relative number of slow oxidative fibers increase
-inactivity leads to fibrosing of skeletal muscle -overall decrease of skeletal muscle. |
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What are some muscle disorders?
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myasthenia gravis and muscular dystrophy.
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What is myasthenia gravis?
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an automimmune disorder where antibodies bind to acetylocholine receptors, inactivating them The patient develops progressive muscle weakness
-initial symptoms often develop in the muscles of the face and neck. -if death occurs it can be associated with paralysis of the respiratory muscles. |
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What is muscular dystrophy?
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a group of genetic disorders associated with degeneration of the skeletal muscles.
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