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36 Cards in this Set
- Front
- Back
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What is the Sliding Filament Mechanism? |
CA2+ increase starts filament sliding (contraction) CA2+ decrease ends filament sliding (no contraction) |
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What is the process of contraction for sliding filament mechanism? |
Thin filaments slide over thick filaments toward center of A-band this causes filaments to contraction and results in the Z-line being pulled closer together End result: Sarcomere Shortens |
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Do all sarcomeres in a muscle fiber shorten at the same time? |
Yes, they do. |
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What is Power Stroke? |
Cross bridge is activated, bends toward center of thick filaments and pulls thin filaments inwards |
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What is the process of Power Stroke? |
Sarcoplasmic reticulum releases CA2+ into sarcoplasm Myosin heads bind to actin Myosin heads swivel toward center of sarcomere ATP binds to myosin head causing myosin head to detach from actin Hydrolysis of ATP transfer energy to myosin head and reactivates (basically starts cycle over) Contraction continues if: 1. ATP is available 2. CA2+ in sarcoplasm is high |
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What is the Sarcoplasmic Reticulum |
It is a revised 'endoplasmic reticulum'. Consists of fine network of interconnected compartments that surround the myofibril not continuous but encircles the myofibril through its length segments wraps around A-band and I-band; forms sac-like regions called terminal cisternae (lateral sacs) |
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What is terminal cisternae and what is it also known as? |
Terminal cisternae are sac-like regions that surround the A-band and I-band Also known as lateral sacs |
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What happens with relaxation? |
Depends on the reuptake of CA2+ into sarcoplasmic reticulum
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What is the process of relaxation? |
Acytecholinerase breaks down ACH at the neuromuscular junction muscle fibers action potential stops When action potential stops, CA2+ is moved back into the sarcoplasmic reticulum |
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What are Transverse Tubules (T-Tubules) |
They are perpendicular from surface of muscle cell membrane and goes into the central portion of muscle fiber When action potential spreads across surface and goes down the t-tubules it causes the release of CA2+ from sarcoplasmic reticulum into sarcoplasm |
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What is the process of Excitation-Contraction coupling? |
1. Action potential arrives from motor nerve 2. Triggers release of ACH from nerve terminals 3. Action potential goes down T-Tubules and plasma membrane 4. This causes the release of CA2+ from sarcoplasmic reticulum into sarcoplasm 5. Actin-myosin interact: cross-bridge formation, power stroke; repeat 6. Ca2+ moves back into sarcoplasmic reticulum and muscles relax |
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What is a twitch? |
Short, brief and weak contractions Useless Doesn't take place in the body
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What two factors affect gradation of muscles? |
1. The number of muscle fibers contracting within a muscle
2. tension developed by each contracting fiber |
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Where is muscle tension formed? |
Within sarcomere
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What needs to happen before bone can be moved? |
Tension transmitted to bone by Connective tissue and tendons |
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What two places to muscles attach across a joint? |
1. Origin --> stationary part of bone
2. Insertion--> movable part of bone |
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What are the types of contractions? |
1. Isotonic 2. Isometric
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What is isotonic contractions? |
muscle tension remains constant as muscle changes |
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What are two types of isotonic contractions? |
Concentric contractions--> muscle shortens
Eccentric contractions--> muscle lengthens |
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What is isometric contractions? |
muscle is prevented from shortening tension is developed at constant muscle length |
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Describe Motor Unit Recruitment |
One motor unit and muscle fibers from it the number of muscle fibers from it can vary |
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Muscles that produce fine, delicate movements would have more or less muscle fibers? |
Would have fewer fibers per unit |
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Muscles that perform large, coarsely controlled movements would have more or less muscle fibers? |
Would have more muscle fibers per unit |
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What helps delay or prevent fatigue? |
Asynchronization recruitment of motor units |
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What factors influence the extent of which tension develops? |
Frequency of stimulation Length of fiber at onset of contraction Extent of fatigue Thickness of fiber |
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What is Twitch Summation |
Results from sustained elevation of cytosolic acid |
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What is Tetanus? |
Muscle is stimulated so rapidly that it doesn't have a chance to relax between stimuli Contraction is 3-4 times stronger than a twitch |
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What are the steps of contraction-relaxtion? |
Splitting of ATP by myosin ATPace provides energy for power stroke at cross bridge Binding of fresh ATP molecule to myosin lets it detach from actin filaments at end of power stroke so cycle can be repeated the active transport of CA2+ back to sarcoplasmic reticulum depends on the energy derived from breakdown of ATP |
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What are the energy sources for contraction? |
1. Transfer of high-phosphate protein from creatine phosphate to ADP (it is the first energy storehouse that is tapped at onset of contraction)
2.Oxidative Phosphorylation (citric acid cycle and electron transport chain)--> takes place within muscle mitochondria and if oxygen is available
3. Glycolysis--> supports anaerobic and high-intensity exercises |
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What happens during Muscle Fatigue? |
Muscle can no longer respond to stimulation with same degree of contractile activity
The defense mechanism that protects muscle from reaching point at which energy (ATP) is no longer produced
Causes are unclear |
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How are the Major types of Muscle Fibers classified? |
based not he differences in ATP hydrolysis and synthesis |
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What are the 3 types of muscle fibers? |
Type 1: slow oxidative Type 2: fast oxidative Type 3: fast glycolic |
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Where are smooth muscles found? |
Hollow organs and tubes |
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What are smooth muscles like? |
No striations and is mono nucleated (one nuclei) Not arranged in sarcomere pattern Cells are usually arranged in sheets within muscle Dense bodies with some proteins also found in Z-line |
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What 3 filaments do smooth muscles have? |
1. Thick Filament --> longer than this in skeletal 2. Thin filament --> has tropomyosin but lacks troponin 3. Intermediate Filament--> not directly involved in contraction, it forms the cytoskeleton that supports the cell shape |
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What are the properties of Cardiac Muscle? |
Striated Mono-nucleated (one nuclei) cells interconnected by gap junctions fibers joined by branching networks Innervated by ANS (autonomic nervous system) |
