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26 Cards in this Set
- Front
- Back
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In skeletal muscle, what are the A, I, and H bands, and what are the Z discs? |
A band- anisotrophic dark band, thick and thin alternating filament region I band- isotropic light band, thin filament region H band- central area with only thick filament Z disc- anchors elastic and thin filaments, one z disc to next is a sarcomere |
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Where do the cell bodies of somatic motor neurons reside?
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Brainstem and spinal cord |
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What is a motor unit?
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Motor unit: each motor neuron and all the muscle fibers it innervates |
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What is the purpose of having some muscles with very large motor units and others with many very small motor units?
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Purpose: provides ability to sustain long-term contraction as motor units take turns resting (postual control) |
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What structure of the body has very small/large motor units that control its movement?
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Large motor unit: for strength and power, 1000 muscle fibers per nerve fiber. (ex. gastrocnemius Small motor unit: fine control, has 20 muscle fibers per nerve fiber (ex. eye muscle) |
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What is the neurotransmitter of neuromuscular junctions (NMJ)?
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Neuromuscular Junction: functional connection between nerve fiber and muscle fiber Neurotransmitter: released from nerve fibers to stimulate muscle cells and initiate contraction. |
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What ion flows into the nerve terminal of the NMJ prior to the release of neurotransmitter to the synaptic cleft?
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Ca2+ flows into the synaptic knob prior to the release of neurotransmitter |
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What organelle is found in abundance in the nerve terminal near the neurotransmitter filled vesicles?
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mitochondria are abundantly found in the nerve terminal near the neurotransmitter filled vesicles |
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What is the difference between a ligand gated channel and a voltage gated channel of the postsynaptic membrane (what specifically triggers opening of the gate)? |
Ligand gated: Acetylcholine triggers the opening of the gate Voltage gated: EPP triggers the opening of this gate (check the last two) |
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Where precisely are acetylcholine receptors of the NMJ located?
Are these muscarinic or nicotinic receptors? |
Definition 21 The acetylcholine receptors are located in the junctional folds of the muscle cell They are nicotine receptors |
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What type of muscle impairment will be caused by pesticide poisoning that inhibits cholinesterase?
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Neuromuscular impairment: Pesticides will bind to acetylcholinesterase and prevent degradation of acetylcholine, so it will cause spastic paralysis and possible suffocation |
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By what mechanism does Tetanus toxin affect muscle?
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Tetanus- caused by toxin Clostridium bacteria, blocks glycine (inhibitory neurotransmitter in spinal cord) release in spinal cord and causes overstimulation of the muscles and spastic paralysis |
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How about curare?
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Curare- causes flaccid paralysis and respiratory arrest because it completes with acetylcholine at nicotine Ach receptors |
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How about botulinum toxin?
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Botulism- food poisoning caused by bacterium clostridium botulinum, blocks release of Ach and causes flaccid muscle paralysis |
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Describe the resting membrane potential (RMP).
What is the voltage of the RMP in muscle? |
RMP: an excess of Na+ and other cations outside the cell and excess negative ions inside the cell creating a difference in charge across the membrane Voltage of the RMP in muscle: -90mV |
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Describe an action potential?
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Quick up and down voltage shift.... depolarization and then repolarization |
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What is depolarization and what is repolarization?
What ionic events are taking place during these components of an action potential? |
Depolarization- when the inside of the plasma membrane briefly becomes positive because of the rush of Na+ into the cell Repolarization- when the inside of the cell becomes negative again because after depolarization, the inside is too positive so Na+ gates close, K+ gates open to allow K+ to come out of the cell |
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What is an end plate potential (EPP)?
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End Plate Potential (EPP): the rapid fluctuation in membrane voltage at the motor end plate Na+ enters, shifting RMP goes from -90mV to +75mV, then K+ exits and RMP returns to -90mV - quick voltage shift is called an end-plate potential (EPP). |
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What is excitation-contraction coupling?
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Excitation-contraction coupling- when an action potential on the sarcolemma activates myofilaments for contraction |
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What is the power stroke of muscle contraction?
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Power stroke- myosin head releases ADP and Pi as it flexes pulling the thin filament past the thick |
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What is the cause of rigor mortis?
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Deteriorating sarcoplasmic reticulum releases calcium activates myosin and actin cross bridgesàmuscles stay contracted and cannot relax because you need ATP to relax them (after death you cannot produce ATP) |
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Where is calsequestrin found and what is its function?
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Found in the Sarcoplasmic Reticulum Function: binds calcium to hold it in the sarcoplasmic reticulum during muscle relaxation |
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Discuss the disease process of Myasthenia Gravis
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Progressive weakness that remits with rest and is worsened by exercise Autoimmune disease |
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What binds to ACh receptors?
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Antibodies bind to Ach receptors |
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What are some of the signs of this disorder?
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Signs- drooping eyelids, double vision, difficulty swallowing, respiratory failure, weak limbs |
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What are the treatment options available? |
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