Term
| What are the three structures that directly control muscle contraction? |
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Definition
1. the muscle itself
2. the nerve that supplies the muscle
3. the synapse between the muscle and nerve |
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Term
| What does Huxley's Sliding Filament Theory explain? |
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Definition
| how skeletal cells contract |
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Term
| What does Huxley's Sliding Filament state? |
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Definition
| muscle contraction is based on the shortening of sarcomeres throughout the skeletal muscle |
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Term
| What are the contractile elements of a sarcomere? |
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Definition
| thick filaments, thin filaments, calcium ions, and ATP |
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Term
| Describe thick filaments. |
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Definition
| multiple two-headed myosin molecules banded together |
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Term
| What are thin filaments made of? |
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Definition
| troponin, tropomyosin, and actin |
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Term
| What are the stages of the contraction cycle? |
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Definition
1. relaxed muscle
2. action potential along nerve
3. cross-bridge attachment
4. power stroke
5. cross-bridge detachment
6. myosin head activation
7. return to relaxed state |
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Term
| What happens during the relaxation stage of the contraction cycle? |
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Definition
-there is minimal filament overlap
-there is no action potential
-tropomyosin covers the myosin head binding sites
-myosin heads are active and holding ATP
-no Ca2+ is present in cytoplasm |
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Term
| What happens during the action potential alon the nerve stage of the contraction cycle? |
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Definition
-action potential is sent along the nerve that innervates the muscle
-Ca2+ enters the cytoplasm
-Ca2+ binds with troponin and causes it to change shape |
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Term
| What happens during the cross bridge attachment stage of the contraction cycle? |
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Definition
-tropomyosin is pulled away from myosin binding site on actin
-active myosin head binds with myosin binding site on actin |
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Term
| What happens during the power stroke stage of the contraction cycle? |
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Definition
-energy from ATP is used to cause flexion and pivoting of the myosin head and tail
-pulls thin filament along thick filament
-sarcomere shortens |
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Term
| What happens during the cross bridge detachment stage of the contraction cycle? |
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Definition
-power stroke stage is repeated to continue shortening the muscle
-ATP binds with myosin head and causes it to release |
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Term
| What happens during the myosin head activation stage of the contraction cycle? |
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Definition
| -myosin ATPase cuts ATP into ADP and inorganic phosphate and potential energy is then stored in myosin head |
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Term
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Definition
| a structure that tells the skeletal muscle what to do and when to do it |
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Term
| What is found on the nerve side of the neuromuscular junction? |
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Definition
-axon
-terminal bouton
-synapse |
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Term
| What is significant about the axon of the motor nerve? |
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Definition
| it comes directly from the spinal cord |
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Term
| What does the terminal bouton contain? |
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Definition
-synaptic vesicles
-calcium channels |
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Term
| What is significant about the synaptic vesicles in the terminal bouton? |
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Definition
| they contain acetylcholine |
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Term
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Definition
| neurotransmitter that functions as a ligand |
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Term
| What is significant about the calcium channels in the terminal bouton? |
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Definition
| they are embedded in the plasma membrane of the nerve |
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Term
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Definition
| the area where nerve joins muscle; structures don't actually touch |
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Term
| What is found on the muscle side of the neuromuscular junction? |
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Definition
-sarcolemma
-junctional folds
-acetylcholine receptors |
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Term
| What is significant about the sarcolemma in regards to the neuromuscular junction? |
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Definition
| it is the plasma membrane of skeletal muscle; forms the "motor end plate" |
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Term
| What are junctional folds? |
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Definition
| folds of the sarcolemma that increase the surface area |
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Term
| What is the purpose of acetylcholine receptors? |
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Definition
| found within junctional folds; act as receptors for acetylcholine |
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Term
| What is the synaptic cleft? |
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Definition
| the "space" between the nerve and muscle |
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Term
| What does the action potential do? |
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Definition
| causes a voltage change in the plasma membrane of terminal bouton |
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Term
| What does the voltage change from the action potential cause? |
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Definition
the Ca2+ channels open to allow Ca2+ to enter the terminal bouton, causing:
-vesicle migration
-vesicles to fuse
-acetylcholine is released |
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Term
| What does the acetlycholine release cause? |
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Definition
-crosses the synapse and binds with recepters
-sarcolemma generates graded potential
-wave of depolarization follows and causes an action potential
-acetylcholine is hydrolized |
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Term
| Why do we want to remove acetlycholine? |
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Definition
| if we didn't remove it, there would be a constant action potential always going |
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Term
| What does excitation-contraction coupling explain? |
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Definition
| when you excite a cell, a contraction WILL follow |
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