Term
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Definition
- Spindle-shaped, nonstriated, uninucleated fibers
- Occur in walls of internal organs
- Involuntary
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Term
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Definition
- Striated, branched, and generally uninucleated fibers.
- Occurs in the walls of the heart.
- Involuntar
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Term
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Definition
- Striated, tubular, multinucleated fibers.
- Voluntary
- Connect via tendons to bones
- Insertion is on the end that moves.
- Move only one bone (but multiple muscles can move the same bone).
- Work in "Antagonistic Pairs"
- Shorten when contracting; can only pull not push.
- Muscles work in opposite pairs. The muscle that does the most work is called the prime mover and the one that does the least the antagonist.
- Muscles can only actively contract.
- Must be lengthened by another muscle.
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Term
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Definition
- A muscle fiber is a cell containing the usual cellular components but special names have been assigned to some of their components
- Sarcolemma: the plasma membrane
- Sarcoplasm: cytoplasm
- sarcoplasmic reticulum: endoplasmic reticulum
- T (transverse) tubules: the Sarcolemma forms a membranous channel that extends inward into the cells
- Myofibrils: Sarcolemma encases hundreds of these. They are the contractile portions of the muscle fibers
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Term
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Definition
- Whole bundle is a muscle fiber.
- Consist of sacromeres
- striated
- extend between two dark vertical lines called Z-lines
- contain even smaller cylinders called myofilaments
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- myosin - thick
- actin - thin
- The I-bands on either side of the Z-line contain thin actin myofilaments
- The central A-band within the sacromere is composed of layered actin & myosin filaments
- Centered within the A-band is the H-zone containing just myosin myofilaments.
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Term
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Definition
- When muscles are stimulated, electrical signals travel across the sarcolemma and then down the T-tubule.
- Actin filaments move past myosin filaments which causes the Z-line to move inward, I-band to shorten, and the H-zone to almost or completely disappear.
- ATP supplies the energy for muscle contraction.
- Myosin filament break down ATP and their cross-bridges pull the actin filament toward the center of the sarcomere.
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Term
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Definition
- Muscle fibers are stimulated to contract by motor neurons whose axons are grouped to form nerves.
- The axon of one motor neuron can stimulate from a few to several muscle fibers of a muscle because each axon has several branches.
- Each branch of an axon ends in an axon terminal that lies in close proximity to the sarcolemma of a muscle fiber. A small gap called a synaptic cleft separates the axon terminal from the sarcolemma.
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Term
| Steps for Muscular Contraction |
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Definition
- Stimulus or mental thought.
- CNS reacts
- CNS interneurons send nerve signals down motor units.
- Synapsis occurs between axon terminals and muscle fibers between synaptic cleft.
- Muscular contraction in muscle fibers.
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Term
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Definition
- Nerve signals travel down the axons of motor neurons and arrive at the axon terminal.
- This action potential at the axon terminal causes a Ca2+ influx.
- THis signal triggers the synaptic vesicles to release ACh neurortransmitters into the synaptic cleft.
- When ACh is released, it quickly diffuses across the cleft and binds to receptors in the sarcolemma of the receiving muscle fiber.
- This opens the sodium/potassium channel causing Na+ to rush in and then K+ to rush out which triggers action potential.
- The action potential in the sarcolemma is spread across the sarcolemma and into the T-tubules, depolarizing the inner portion of the muscle fiber.
- This then causes the release of Ca2+ from the sarcoplasmic reticulum and diffuse into the myofibrils.
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Ca2+ binds with troponin present on actin allowing muscular contraction to occur.
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Term
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Definition
- The heads of myosin filament have ATP binding sites. At this site, ATP is hydrolyzed, split, to form ADP and P.
- The ADP and P remain on the myosin heads while the heads attach to an actin binding site. Joining myosin to actin forms temporary bonds called cross-bridges (converting energy (ATP) into force & motion).
- ADP and P are released and the cross-bridges bend sharply. This is the power stroke that pulls actin filaments toward the center of the sarcomere, contraction (middle of the A-band?).
- When ATP molecules again bind to the myosin heads, the cross-bridges are broken. Myosin heads detach from the actin filament.
- The cycle recurs until calcium ions are actively returned to the sarcoplasmic reticulum (also requiring ATP) during synapsis.
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Term
| ATP for Muscle Contraction |
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Definition
- Muscles store limited amounts of ATP
- ATP store can be used up in a few seconds during strenous contractions
- Sources
- creating phosphate pathway
- fermentation
- cellular respiration
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Term
| Creatine Phosphate Pathway |
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Definition
- Simplest and most rapid way (because its only one reaction)
- Occurs in the midst of sliding filaments (therefore quickest)
- Creating phosphate is formed only when muscle is resting (limited amount stored)
- ADP --> ATP
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Term
| fermentation: "Oxygen Debt" |
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Definition
- Amount of oxygen needed to metabolize lactate.
- Lactate is transported to the liver where 20% is broken down to CO2 and H2O. The ATP gained by this respiration is used to reconvert 80% of the lactate to glucose and then glycogen.
- Number of mitochondria increase.
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Term
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Definition
- Fast acting but results in a buildup of lactate.
- No oxygen required/present.
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Term
| cellular respiration in muscles |
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Definition
- Slowest of all 3 mechanisms but most efficient.
- Occurs in the mitochondria.
- Uses glucose from the breakdown of stored muscle breakdown of stored muscle glycogen and/or fatty acids from fat digestion.
- Process requires O2 supplied by the respiratory system.
- Protein , myoglobin (stronger affinity than hemoglobin), found within muscle cells delivers O2 as well
- Produces CO2, H2O and heat (ATP).
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Term
| Muscles can tolerate lack of oxygen longer than other tissues |
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Definition
- Training increases number mitochondria
- Cellular respiration better chance of keeping up with demand
- Marathon runners typically use up all the muscle and liver’s glycogen supply
- Not limited by fatigue
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Term
| Regulation of Muscle Shortening |
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Definition
- Tropomyosin (and troponin) block muscle contractions until calcium ions (from synapsis) are present
- Threads of tropomyosin wind about an actin filament covering binding sites for myosin located on each actin molecules
- Troponin occurs at intervals along the threads.
- When Ca2+ ions are released from the sarcoplasmic reticulum, they combine with troponin.
- This causes the tropomyosin threads to shift their position, exposing myosin binding sites and allowing myosin to bind to actin.
- Troponin cancels out tropomyosin allowing muscle contraction to occur.
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Term
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Definition
| Threads wound about actin filament binding sites that block muscle contractions until calcium ions (from synapsis) are present. |
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Term
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Definition
| Causes tropomyosin threads to shift their position, exposing myosin binding sites and allowing myosin to bind to actin. |
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Term
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Definition
- Motor Unit: A nerve fiber with all of the muscle fibers it innervates
- Either all the muscle fibers in a motor contract or not, all are stimulated at once.
- Twitch: When a motor unit is stimulated by infrequent electrical impulses a single contraction occurs.
- Tetanus
- Sustained muscle contraction without relaxation, caused by a motor unit being given a rapid series of stimulii
- Continues until the muscle fatigues due to lack of energy.
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Term
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Definition
- Dependent on muscle contraction
- Some motor units are always contracted (causing firm muscles vs. flabby ones) but not enough to cause movement.
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Term
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Definition
- Slow-twitch muscle fibers
- Requires oxygen
- Has endurance
- Fast-Twitch muscle fibers
- Anaerobic
- Fatigues quickly b/c they depend on anaerobic energy, lactate buildup
- Less mitochondria, myoglobin, and sparser blood supply
- "Red Fibers"
- Lots of mitochondria and myoglobin
- Rich blood supply, large reserves of glycogen and fat.
- Contract relatively slowly but have high endurance.
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Term
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Definition
- Sudden and involuntary muscle contractoins.
- Occur in smooth and skeletal muscles.
- A spasm of the intestinal tract is a type of colic (i.e. stomachache)
- convulsion: multiple spasms of skeletal muscles
- cramps: strong, painful spasms
- facial tics: voluntary spasms (i.e. period eye blinking, grimacing)
- tendinits: inflamed tendon by a sprain
- Tendons do not glide easily over bones
- Caused by overuse
- Bursits: inflammation of any friction-ease sacs called bursae within the knee joint
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Term
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Definition
- strain: over-stretching a muscle near a joing
- sprain: twisting of joint causing inflammation of muscles, ligaments, tendons, blood vessels, and nerves
- myalgia:
- Muscles due to influenz, myositis
- Inflammation due to infection and immune disorders
- tennis elbow: tendons get small tears causing pain. Wrist extensors main culprit
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Term
| treatment of arthritis, bursitis, and tendonitis |
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Definition
- Non-steroidal anti-inflammatory drugs
- Ibuprofin (advil), naproxen (Aleve)
- Cortisone injections
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Term
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Definition
- Progressive degeneration and weakening of muscles
- Fibers die, replaced by fat and connective tissue
- Lack of dystrophin
- Inherited sex-linked disorder
- Deuchenne muscular dystrophy most common
- Large protein localized at cell membrane
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Term
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Definition
- connects cortical networks with cytoskeleton.
- Activates calciium-sensitive apoptotic pathways
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Term
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Definition
- Autoimmune disease
- Weakness of eyelids, face & neck extremities
- Antibodies destroy acetylcholine receptors.
- Treat with acetylcholinesterase inhibitors.
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Term
| muscles maintains homeostasis |
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Definition
- Contraction of skeletal muscles push blood back toward the heart
- Cardiac muscle contractions propel blood into the arterial system.
- Skeletal muscle contractions help to squeez tissue fluid into the lymphatic capillaries.
- Smooth muscles contract in blood vessels pulling them away from the surface of the skin, which helps to conserve body heat.
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