18) In response to action potentials arriving fiom the transverse tubules, the s
ID: 302933 • Letter: 1
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18) In response to action potentials arriving fiom the transverse tubules, the surcoplasmic reticulum releases A) acetylcholine. B) sodium ions. C) potassium ions. D) calcium ions. E) all of the above 19) At the neuromuscular junction, the muscle fiber membrane is folded to form a A) motor end plate. B) motor unit. C) neuroreceptor D) neurotransmitter. E) motor neuron. 20) Rigor mortis occurs at death due to a lack of A) cAMP. B) DNA. C) RNA. D) ATP E) tRNA. 21) When a calcium ion binds to troponin, A) tropomyosin moves out of the groove between the actin molecules. B) active sites on the myosin are exposed. C) actin heads will bind to myosin. D) muscle relaxation occurs. E) all of the above 22) Which of the following is the smaller amount? A) the concentration of calcium ions in the sarcoplasm of a resting muscle ot basrod ( B) the concentration of calcium ions in the sarcoplasmic reticulum ofa resting muscle hosloold 23) Myasthenia gravis is an autoimmune disorder in which antibodies attack acetylcholine receptors. The resulting muscle weakness is likely due to A) increasing the amount of acetylcholinesterase in the synapse. B) making the cells less permeable to sodium ions. C) increasing the amount of potassium ion in the intercellular fluid. D) making the plasma membranes more permeable to calcium ion. E) antibodies competing with acetylcholinesterase for acetylcholine 24) An example of partial but sustained contraction is A) treppe B) tetany C) a twitch. D) fatigueExplanation / Answer
18 answer: Calcium ions.
it is the calcium ion which decide whether or not contraction can occur. when depolarization of T tubules occur voltage sensor changes its conformation . this change in conformation causes calcium ions channels to open and alllow calcium ions release.
19 answer: at the end of the neuromuscular junction, muscle fiber membrane is folded to form a motor end plate
axon of a motor neuron makes synaptic contact with striated muscle fiber by the help of this large and complex terminal . it has nocitinic acetyl choline receptors. when the acetylcholine binds to its receptor, muscle fiber releases sodium ion which depolarises sarcolemma.
20 answer: rigor mortis occurs at death due to the lack of ATP
because of the lack of ATP , there is no myosin shifts so muscles remain contracted.
21 answer: when active sites on the myosin are exposed - calcium ions bind to troponin.
22 answer: A , the concentration of calcium ions in the sarcoplasm of a resting muscle
23answer : increasing the amount of acetylcholinesterase in the synapse
24answer:. tetany
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