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62 Cards in this Set
- Front
- Back
What kind of receptor does ACh bind to on muscle motor endplates?
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Nicotinic receptors
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What creates the end-plate potential (EPP)?
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Net influx of Na+ through ligand gated channels depolarizes the muscle membrane (step 4)
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What is the 1st step in converting an electrical signal to a mechanical response?
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Action potential of somatic motoneuron reaches nerve terminus
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What is the 2nd step in converting an electrical signal to a mechanical response?
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Voltage gated Ca++ channels on the nerve open. Ca++ entry into the nerve endings triggers exocytosis of ACh containing vesicles
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What is the 3rd step in converting an electrical signal to a mechanical response?
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Acetylcholine diffuses into synaptic cleft and binds to nicotinic channel receptors on muscle motor endplate.
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What is the 4th step in converting an electrical signal to a mechanical response?
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Net influx of Na+ through the acetylcholine (ligand) gated channels depolarizes the muscle membrane, creating an end-plate potential (EPP). In normal situations, the EPP always creates a muscle action potential.
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What is the 5th step in converting an electrical signal to a mechanical response?
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The action potential spreads from the neuromuscular junction along the fiber membrane and through the t-tubules.
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Where is the terminal cistern located?
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On either side of a T-tubule. Between a T-tubule and the sarcoplasmic reticulum.
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What does the sarcoplasmic reticulum contain?
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Things like Ca++
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What is the 6th step in converting an electrical signal to a mechanical response?
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Voltage sensitive DHP receptors in the T-tubule allow Ca++ to enter the cell into the terminal cistern area.
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What type of calcium channel are DHP receptors?
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DHP receptors are a type of L-type calcium channel
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What causes ryanodine channels on the sarcoplasmic reticulum to open?
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The increase in intracellular calcium causes ryanodine channels to open
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What is one T-tubule and two cisterns?
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A Triad
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What is the purpose of T-tubules?
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To disseminate the energy down into a muscle cell
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In skeletal muscle, what directly activates the release of Ca++ from the Sarcoplasmic reticulum?
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VDCCs (voltage-dependent calcium channels)
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What signaling molecule triggers muscle contraction?
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Ca++
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What is in the sarcoplasmic reticulum that transports Ca++ back into the lumen, decreasing the cytoplasmic Ca++ concentration, and the muscle relaxes?
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Ca++-ATPase in the sarcoplasmic reticulum
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What types of muscle use VDCCs to allow entry of Ca++?
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Skeletal and Cardiac Muscle
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What is a calcium channel blocker used for treatment of hypertension?
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DHP = dihydropyridine, nifedipine
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What allows myosin to release inorganic phosphate from ATP hydrolysis and complete the power stroke?
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Ca++ binding to troponin, pulling tropomyosin off the myosin binding site of actin
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What happens at the end of a power stroke under normal circumstances?
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The myosin cross bridges release ADP and remain tightly bound to actin until ATP binds the myosin head and releases it from the binding site.
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What makes myosin heads lock in a state of rigor?
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No ATP to release the head
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When does the muscle fiber relax? (chemically)
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When Ca++ is transported back into the sarcoplasmic reticulum
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What causes hydrolysis of ATP in the cross-bridge cycle?
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The myosin head acts as an ATPase
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What is a ball at the end of the nerve ending. Inside of which are synaptic vesicles created within the neuron?
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Presynaptic Bouton (nerve terminus)
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What contains the neurotransmitters and can have 100s or 1000s in a bouton?
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Synaptic Vesicles
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What determines how much time it will take from the release of a neurotransmitter to stimulate the contraction of the muscle?
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The distance of the Synaptic Cleft
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What is a type of SNARE protein, involved in the fusion of membranes in the exocytosis of vesicles?
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Synaptobrevin
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What protein regulates the number of synaptic vesicles available for exocytosis?
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Synapsin
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What does the amount of neurotransmitter released depend upon?
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The number of vesicles that fuse with the presynaptic membrane in response to Ca++ influx
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T/F The motor end plate is a receptor region -- it contains lots of receptors specific for a particular neurotransmitter.
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True
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what does a Ligand Gated Sodium Channel activate?
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ACh binds and Na+ enters the cell
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T/F
Ligand gated sodium channel receptors has 2 binding sites for ACh but only one need to be bound to ACh for the response to occur. |
False
Both need to be bound to occur |
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What happens as more and more ligand gated sodium channel receptors bind to ACh?
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The muscle stimulation gets bigger and bigger
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What is the change in membrane potential induced by the action of multiple mini end plate potentials called?
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The End Plate Potential
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What molecule is primarily involved in the depolarization of the myocyte?
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Na+
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What molecule is more significant than Na+ at the synaptic cleft?
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Ca++
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What molecule sets off a cascade which causes the NT vesicles inside the motor neuron to migrate to the synaptic cleft and release ACh?
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Ca++
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What is the primary NT substance released by motor neurons to stimulate a skeletal muscle contraction?
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ACh
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What is bound to the motor end plate region and helps to degrade ACh and allows for its resorption back into the bouton?
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Acetylcholineesterase
(ACh-Esterase) |
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What toxin is found in blow fish and blocks Na+ channels on BOTH the nerve process and the muscle cell?
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Tetrodotoxin
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What blocks ACh release into the synaptic cleft by dissolving SNARE proteins in the motor neuron?
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Tetanus and Botulinus Toxin
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What are Reversible cholinesterase inhibitors?
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Physostigmine & Neostigmine
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What are Irreversible cholinesterase inhibitors found in fertilizers?
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Organophosphate
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What facillitates binding of ACh at the motor end plate?
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Nicotine and ACh
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What are Fast Acting competative inhibitors competing for ACh receptors?
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Alpha-bungarotoxin (Cobra Venom)
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What are Slow Acting competative inhibitors competing for ACh receptors, used in surgery for temporary relaxation of muscles?
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Turbocurrarine (curare)
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What blocks potassium channels, preventing repolarization? (has the same effect as a cholinesterase inhibitor)
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Dendrotoxin (mamba venom)
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What type of receptor has:
Ligand gated ion channel Open or close in response to a chemical stimulus Nicotinic Receptor |
Ionotropic Receptor
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What type of receptor:
Do not form an ion channel pore Instead, are indirectly linked with ion-channels on the plasma membrane of the cell through signal transduction mechanisms When the NT is released and attaches to the metabotropic receptor, it initiates a G-protein cascade Muscarinic Receptor |
Metabotropic Receptor
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Where is Troponin T?
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Attached to tropomyosin
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Where is Troponin I?
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Attached to actin
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Where is Troponin C?
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Troponin C is the Ca++ binding site
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When Troponin I is attached to actin what happens?
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It is Inactive (get it...I, oh the irony of nomenclature)
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T/F
The myosin has a tail and a hinge as well as multiple heads. On the head, there is an alkali component that helps stabilize it. There is also a regulatory component that regulates ATPase. |
True
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how summation occurs and what is the final result
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summation is the frequent delivered stimuli (not enough time for complete relaxation) increases the contractile force
finally become tetanus |
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explain the treppe staircase effect:
causes? |
increased contraction in response to multiple
stimuli of the same strength (the later contractions have a greater amplitude than earlier ones) increase availability of Ca ion in the sarcoplasm enzyme is heated up |
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isotonic contraction explain
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the muscle changes in length (decreasing the angle of the joint) and moves the load
once the muscle overcome the threshold, muscle can shorten |
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isometric muscle explain
give one example |
Muscle exerts force without changing length
Pulling against immovable object the threshold is not reached. postural muscle |
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slow twitch and fast twitch fibres (type 1 and 2)
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Differences due to different myosin ATPase isoenzymes are slow or fast
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slow twitch muscle
how? |
Slow-twitch (type I fibers):
• Red fibers. = • High [myoglobin]. • High oxidative capacity for aerobic respiration. • Resistant to fatigue. • Have rich capillary supply. • Numerous mitochondria and aerobic enzymes. example: • Soleus muscle in the leg. |
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fast twitch how and what?
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• Intermediate (type II A)
fibers: • Great aerobic ability. • Resistant to fatigue. • Fast-twitch (type IIX fibers): • White fibers. • Adapted to respire anaerobically. • Have large stores of glycogen. • Have few capillaries. • Have few mitochondria. • Extraocular muscles that |