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46 Cards in this Set
- Front
- Back
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Stimulation ONLY occurs when stimulated by:
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Somatic motor neurons
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Describe the breakdown of a muscle cell:
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1 muscle cell = muscle fiber
1 muscle fiber consists of many bundles. 1 msucle bundle = 1 myofibril Each muscle bundle consists of thick and thin filaments. |
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Describe the breakdown of a muscle cell:
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1 muscle cell = muscle fiber
1 muscle fiber consists of many bundles. 1 msucle bundle = 1 myofibril Each muscle bundle consists of thick and thin filaments. |
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Filaments are arranged in repeating units called:
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Sarcomeres (Z-disk to Z-disk)
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Filaments are arranged in repeating units called:
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Sarcomeres (Z-disk to Z-disk)
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Why do sarcomeres shorten?
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Because the filaments overlap.
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Why do sarcomeres shorten?
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Because the filaments overlap.
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On which filaments do the cross bridges reside on? Where do they bind to?
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Thick filaments, and they bind to thin filaments and pull on them (cross bridge cycling)
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On which filaments do the cross bridges reside on? Where do they bind to?
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Thick filaments, and they bind to thin filaments and pull on them (cross bridge cycling)
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What's the role of ATP?
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Helps to detach the cross bridge (breaks the rigor bond) and provides energy for the next cycle.
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What's the role of ATP?
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Helps to detach the cross bridge (breaks the rigor bond) and provides energy for the next cycle.
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What's the role of Ca?
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It allows the cycles to occur.
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What's the role of Ca?
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It allows the cycles to occur.
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What happens when you don't have Ca? and don't have ATP?
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No Ca--> No binding, no cycling.
No ATP---> rigor mortis |
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What is each myobril surrounded by?
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A tubular network called the sarcoplasmic reticulum (SR) that is loaded with Ca.
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What tubules penetrate between sections of SR?
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T-tubules.
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What happens when you don't have Ca? and don't have ATP?
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No Ca--> No binding, no cycling.
No ATP---> rigor mortis |
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What is each myobril surrounded by?
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A tubular network called the sarcoplasmic reticulum (SR) that is loaded with Ca.
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What tubules penetrate between sections of SR?
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T-tubules.
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What happens when an AP propagates along the surface membrane?
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It also propagates down the T-tubules.
As a result, Ca is released from SR. The released Ca binds to troponin briefly causing tropomyosin to expose cross bridge binding sites. Cross bridges cycle until Ca is removed by Ca-ATPase. A brief contraction is called a twitch. |
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Char of a twitch
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May not have a refractory period if the two APs are close enough to one another.
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Dystrophin Complexi
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A link between contractile proteins and fiber encased by CT.
Convey force across membrane from the contractile proteins to CT outside. |
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T or F. Single motor neuron innervates a group of fibvers.
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True
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T or F Each motor neuron forms many synapses (NMJ) with every fiber in its motor unit.
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True
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T or F Each AP causes a big EPSP and every fiber in that motor unit fires.
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True
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What determines whole muscle force?
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1. Number of active motor units
2. Type 3. Frequency of APs 4. Length of muscle |
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Concerning length tension, largest force is at?
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Maximum physiological length (at 100%)
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What are two types of motor units?
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Slow oxidative (red)
Fast glycolytic (white) |
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Slow oxidative (red)
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Fatigue slowly
Used for ongoing tasks and delicate tasks. Weak |
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Fast glycotic (white)
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Strong
Fatigue rapidly Recruited for intense contractions. |
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Smooth muscle vs. skeletal muscles
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Smooth muscle cells are much smaller.
No t-tubules (don't need them) No repeated sarcomeres, but they have thick and thin filaments. |
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Properties of Smooth Muscles
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Each cell develops variable force. (no single twitches or fused tetanus).
Phasic (i.e. contraction then relaxation) smooth muscle. Tonic smooth muscle (i.e. walls of large arteries) Constant force (latch state) for long periods sometimes interrupted by relaxations. |
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Receptors on smooth muscles vs. on skeletal
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For skeletal, localized.
For smooth, distributed all over. |
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Sources or controls
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Skeletal--> 1 control (motor neuron)
Smooth--> multiple signals from multiple sources. |
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Cross bridges in skeletal and smooth muscles.
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Skeletal: reside on thick filaments and activated when Ca binds to troponin.
Smooth: No troponin. Cross bridges are activated by phosphorylating light chains. |
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Regulation of light chain phosphorylation:
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Myosin light chain kinase does the phosphorylation of light chains.
Phosphatase removes phosphate. Force is proportional to Kinase activity/phosphatase activity. |
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What is the kinase that does the phosphorylation?
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CAM-kinase. Therefore, Ca plays a crucial role in promoting contractile.
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What are the two pathways for entry of Ca, and thus activation of myosin light chain kinase?
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1. Ca channel
2. Receptor for extracellular signals. |
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In TONIC smooth muscles, do the cross bridges use ATP?
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No. They latch.
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Thick smooth muscle walls vs. thin.
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Thick: in latch state.
Thin: Phasic |
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Nitric oxide
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Relaxes smooth muscles via activating myosin light chain phosphatase.
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Cardiac muscle
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Striated
T-tubule Every cell contracts with every beat. Variable force. Not automatic, but are excited by conduction from other cells via gap junctions. NO NMJ! |
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Cardiac muscle AP
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5 phases
Phase 0: Na in rapidly Phase 1: K and Cl out Phase 2: Ca in and K out Phase 3: K out Phase 4: Flat |
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What determines the strength of ventricular contraction?
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1. Amount of stretch BEFORE each contraction. (length-tension relationship)
2. Amount Ca entering and amount released from SR. |
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Increasing sympathetic stimulation does what to APs?
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Make it stronger and shorter.
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