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60 Cards in this Set
- Front
- Back
- 3rd side (hint)
skeletal ( location, function, appearance, control) |
skeleton, move bone, multi nucleated and striated, voluntary. |
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Cardiac |
heart, pump blood, one nucleus striated and intercalated discs, involuntary |
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Smooth muscle (visceral) |
various organs ex. GI, various functions ex. peristalsis, one nucleus and no striations |
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Epimysium |
outer layer encircling the entire muscle |
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Perimysium |
surrounds groups of 10 to 100 muscle fibers separating them into bundles called fascicles |
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Endomysium: |
penetrates the interior of each fascicle and separates individual muscle fibers from one another |
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Sarcolemma |
the plasma membrane of a muscle cell |
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Sarcoplasm: |
the muscle cell cytoplasm and contains a large amount of glycogen for energy production and myoglobin for oxygen storage. |
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Transverse tubules |
tiny invaginations of the sarcolemma that quickly spread the muscle action potential to all parts of the muscle fiber |
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Sarcoplasmic reticulum: |
encircles each myofibril and is like the smooth endoplasmic reticulum in non-muscle cells and in the relaxed muscle. It functions to store calcium ions |
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Myofibril: |
Threadlike structures extending longitudinally through a muscle fiber consisting mainly of thick filaments (myosin) and thin filaments (actin, troponin, and tropomyosin). |
Within myofibrils are smaller protein structures: |
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Actin: |
thin filaments |
Within myofibrils are smaller protein structures: |
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Myosin: |
thick filaments |
Within myofibrils are smaller protein structures: |
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Why are Sarcomeres and z discs important? ? |
Sarcomeres are the basic functional units of a myofibril. Z discs are regions of dense protein that separate |
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The Arrangement of a Sarcomere |
Two actin filaments overlap one myosin filament and are both involved in the contractile processFilaments are arranged in compartments called sarcomeres |
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Z dics |
Narrow, plate- shaped regions of dense material that separate one sarcomere from the next |
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A band |
Dark, middle part sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments |
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I band |
lighter, less dense area of Sarcomere that contains remainder of thin filaments but no thick filaments. A Z disc passes through the center of each I band |
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H zone |
narrow region in center of each A band that contains thick filaments but no thin filaments |
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M line |
region in center of H zone that contains proteins that hold thick filaments together at center of Sarcomere |
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Contractile |
MyosinActin |
Muscle proteins. Myofibrils are built from three types of protein |
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Regulatory |
TroponinTropomyosin |
Muscle proteins. Myofibrils are built from three types of protein |
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Structural |
TitinNebulinAlpha-actinMyomesinDystrophin |
Muscle proteins. Myofibrils are built from three types of protein |
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Thick filaments |
are mostly myosin and function as a motor proteins that pull various cellular structures to achieve movement |
Muscle proteins: contractile |
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Thin filaments |
are mostly actin twisted into a helix with a binding site for myosin Troponin and Tropomyosin are regulatory proteins that block the myosin binding site in a relaxed state |
muscle proteins: contractile |
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The sliding filament mechanism |
During muscle contraction, myosin cross bridges pull on actin filaments, causing the thin filament to slide inwardConsequently, Z discs move toward each other and the sarcomere shortens Myosin and Actin do not change in lengthThanks to the structural proteins, there is a transmission of force throughout the entire muscle, resulting in whole muscle contraction |
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The Contraction Cycle: ATP Hydrolysis |
myosin heads hydrolyze ATP and become reoriented and energized |
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The Contraction Cycle : attachment |
myosin heads bind to actin, forming cross-bridges |
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The Contraction Cycle: power stroke |
myosin cross-bridges rotate towards center of Sarcomere |
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The Contraction Cycle: detachment |
as myosin heads bind ATP the cross-bridges detach from actin |
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ATP hydrolysis: |
Myosin head includes an ATP-binding site and an ATPase, an enzyme that hydrolyzes ATP into ADP (adenosine diphosphate) and a phosphate group. This hydrolysis reaction reorients and energizes the myosin head. |
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Attachment of myosin to actin to form cross-bridges |
Myosin head attaches to the myosin-binding site on actin and releases the previously hydrolyzed phosphate group (formation of cross-bridges) |
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Power stroke: |
During the power stroke, the site on the cross-bridge where ADP is still bound opens the cross-bridge rotates and releases the ADP The cross-bridge generates force as it rotates toward the center of the sarcomere, sliding the thin filament past the thick filament toward the M line. |
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Detachment of myosin from actin. |
The cross-bridge remains firmly attached to actin until it binds another molecule of ATP.As ATP binds to the ATP-binding site on the myosin head, the myosin head detaches from actin. |
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Excitation-Contraction Coupling |
This concept connects the events of a muscle action potential with the sliding filament mechanism |
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Excitation-Contraction Coupling 2 |
Increase in intracellular Ca2+ starts the contractionAs a muscle action potential propagates along the sarcolemma and into the T tubules, it causes Ca2+ release channels in the SR membrane to open |
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Excitation-Contraction Coupling 3 |
Ca2+ increase occurs because of release from the SR The released calcium ions combine with troponin, causing it to change shape (contraction cycle begins). |
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Excitation-Contraction Coupling 4 |
Ca2+ active transport pumps that use ATP to move Ca2+ constantly from the sarcoplasm into the SR |
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Calesequestrin |
is a calcium binding protein that helps concentrate the Ca2+ near the site for release for the sarcoplasmic reticulum |
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The Neuromuscular Junction (NMJ) The events at the NMJ produce a muscle action potential:1 |
Voltage-gated calcium channels open resulting in an influx of calcium. |
5 steps |
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The Neuromuscular Junction (NMJ)The events at the NMJ produce a muscle action potential: 2 |
This causes exocytosis of neurotransmitter (NT) into the synaptic cleft (Acetylcholine). |
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The Neuromuscular Junction (NMJ)The events at the NMJ produce a muscle action potential: 3 |
NT binds to ligand-gated Na+ channels on the motor endplate which cause an influx of Na+ into the muscle. |
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The Neuromuscular Junction (NMJ)The events at the NMJ produce a muscle action potential: 4 |
This depolarizes it and results in Ca2+ release from the SR |
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The Neuromuscular Junction (NMJ)The events at the NMJ produce a muscle action potential: 5 |
Acetylcholine gets broken down by acetylcholinesterase |
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Muscle Metabolism Creatine phosphate: |
First energy source when muscle contraction begins (first 15 seconds)Excess ATP is used to synthesize creatine phosphate which is used to quickly generate ATP through phosphorylation of ADP |
How do muscles derive the ATP necessary to power the contraction cycle? |
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Muscle Metabolism Anaerobic glycolysis: |
Partial catabolism of glucose to generate ATP occurs in anaerobic cellular respiration Lactic acid is produced and diffuses into bloodThis system can provide enough energy for about 30-40 seconds of maximal muscle activity |
How do muscles derive the ATP necessary to power the contraction cycle? |
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Muscle Metabolism Cellular respiration: |
Aerobic respiration supplies enough ATP for muscles during periods of rest or light to moderate exercise provided enough oxygen and nutrients are availableIn activities that last from several minutes to an hour or more, aerobic respiration provides nearly all the needed ATP |
How do muscles derive the ATP necessary to power the contraction cycle? |
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Muscle Fatigue |
Due to: Inadequate release of Ca2+ from SR Depletion of CP, oxygen, and nutrients Build up of lactic acid and ADP Insufficient release of ACh at NMJ |
The inability to maintain force of contraction after prolonged activity |
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Oxygen Consumption After Exercise Oxygen debt: |
extra oxygen used to pay back or restore metabolic conditions in three ways |
Why do you continue to breathe heavily for a period of time after stopping exercise? |
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Oxygen Consumption After Exercise |
1. Replenish CP stores and ATP in muscle fibers2. Convert lactic acid into pyruvate and glycogen stores in the liver3. Reload O2 onto myoglobin |
Why do you continue to breathe heavily for a period of time after stopping exercise? 3 steps |
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Factors that Influence Muscle Tension |
Amount of tension produced depends on:1. Sarcomere length2. Frequency of stimulation (number of impulses per second)3. Motor unit size Recruitment of motor units |
More tension = generates contraction |
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Length-Tension Relationship |
The force of a muscle contraction depends on the length of the sarcomeres prior to the contraction |
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Length-Tension Relationship |
At a sarcomere length of about 2.0–2.4: Zone of overlap is optimal Muscle fiber can develop maximum tension As the sarcomeres of a muscle fiber are stretched to a longer length:Zone of overlap shortensthe tension the fiber can produce decreases |
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Isotonic contraction: |
tension is constant while the muscle changes lengthUsed for body movements and for moving objectsConcentric isotonic contraction – when the length of the muscle shortens and the object is moved Eccentric isotonic contraction – when the length of the muscle increases or lengthens during contraction |
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Isometric contraction: |
muscle contracts but does not change in lengthImportant in maintaining body posture and position |
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Skeletal Muscle Fiber Types |
Differ in composition, function, myoglobin content, speed of contraction and relaxation, metabolic reactions for ATP generation and how quickly they fatigueSlow oxidative: Small, dark red, fatigue resistantFast oxidative glycolytic: Intermediate size, dark red, moderately resistant to fatigueFast glycolytic: low resistance to fatigue |
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Cardiac Muscle |
Cardiac muscle has the same arrangement as skeletal muscle but also:Intercalated discs – contain desmosomes and gap junctions that allow muscle action potentials to spread from one muscle fiber to anotherContractions last 10 - 15 times longer than skeletal muscle Mitochondria are larger and more numerousStimulated by own autorhythmic muscle fibers |
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Smooth Muscle |
Smooth muscle contractions start more slowly and last longer than skeletal and cardiac muscle contractionsSmooth muscle can shorten and stretch to a greater extentUsually activated involuntarily |
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Smooth Muscle: Single unit (visceral): |
more common and contract as one single unit, similar to cardiac muscle (autorhythmic) |
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Smooth Muscle: Multi-unit: |
consists of individual fibers that contract independently |
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