Now use the below table to compare the muscle contraction problems faced by Jeff and Sandy to that of a person with fully functioning muscles. Use normal, increased, and decreased to complete the table. Each box = 0.5 marks ACh AChE Nicotinic Receptors Na+ influx SR Ca2+ release Crossbridge formation Frequency of muscle contraction Jeff increased Decreased Sandy
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- Normal Muscle Contraction: Acetylcholine (ACh) is released into the synaptic cleft, binds to nicotinic receptors on the muscle cell membrane, causing sodium (Na+) influx, which then triggers sarcoplasmic reticulum (SR) calcium (Ca2+) release, leading to Show more…
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QUESTION: In an accidental poisoning, a dog is found to be in a condition where all of his muscles have gone into a contraction and cannot relax, or when starting to relax, the muscles immediately go back into spasm again. Describe a scenario that could account for this (ie. what did the poison do?). In your answer, you MUST use what you know about what is happening on the cellular and molecular level of muscle contractions. Background of what we have learned in class to help ou answer the question: -excitation-contraction coupling Discussing the skeletal muscular system and action potentials. -voltage-gated Ca+ channels open and diffuse into terminal -Ca+ causes synaptic vesicles to release acetylcholine via exocytosis -acetylcholine diffuses the synaptic cleft and binds to acetylcholine receptors -Na+ ions enter muscle fibers, k+ exit, and action potential created when there is a threshold value in the membrane
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In the disease myasthenia gravis, the human body makes-by mistakeantibodies to its own acetylcholine receptor molecules. These antibodies bind to and inactivate acetylcholine receptors on the plasma membrane of muscle cells. The disease leads to a devastating progressive weakening of the muscles of people affected. Early on, they may have difficulty opening their eyelids, for example, and, in an animal model of the disease, rabbits have difficulty holding their ears up. As the disease progresses, most muscles weaken, and people with myasthenia gravis have difficulty speaking and swallowing. Eventually, impaired breathing can cause death. Explain which step of muscle function is affected.
A group of peptides that influence nerve transmission in certain parts of the brain have been isolated from normal brain tissue. These peptides are known as opioids because they bind to specific receptors that also bind opiate drugs, such as morphine and naloxone. Opioids thus mimic some of the properties of opiates. Some researchers consider these peptides to be the brain's own painkillers. Using the information below, determine the amino acid sequence of the opioid leucine enkephalin. Explain how your structure is consistent with each piece of information. (a) Complete hydrolysis by $6 \mathrm{M}$ HCl at $110^{\circ} \mathrm{C}$ followed by amino acid analysis indicated the presence of Gly, Leu, Phe, and Tyr, in a 2: 1: 1: 1 molar ratio. (b) Treatment of the peptide with 1 -fluoro- 2,4 -dinitrobenzene followed by complete hydrolysis and chromatography indicated the presence of the 2,4 -dinitrophenyl derivative of tyrosine. No free tyrosine could be found. (c) Complete digestion of the peptide with chymotrypsin followed by chromatography yielded free tyrosine and leucine, plus a tripeptide containing Phe and Gly in a 1: 2 ratio.
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