1. Sarin is a synthetic, volatile neurotoxin that can enter the body through the
ID: 3514714 • Letter: 1
Question
1. Sarin is a synthetic, volatile neurotoxin that can enter the body through the eyes, skin, lungs, and Gl tract. Early symptoms of sarin exposure include watery eyes and constricted pupils. Later, more severe symptoms include skeletal muscle paralysis and difficulty breathing. If not treated, paralysis of respiratory muscles leads to death. a) Does sarin affect effectors of the somatic nervous system, autonomic nervous system, neither, or both? Explain. (2 pts) b) Briefly describe the mechanism of action of sarin. (3 pts) c) Explain how sarin causes each: watery eyes, constricted pupils. (4 pts) d) Explain how sarin affects the movement of Nat into a skeletal muscle cell. (2 pts) e) Explain how sarin affects the concentration of Ca2+ in the cytosol of a skeletal muscle cell. (2 pts) f) In a myofibril, how would sarin affect the position of thin filaments relative to thick filaments? Explain. (2 pts) 2. Describe the changes that occur within the left ventricle throughout the course of the cardiac cycle, including changes in (a) pressure, (b) volume, (c) position of the left AV valve (bicuspid), and (d) the aortic semilunar valve. Begin at the onset diastole (relaxation period). (5 pts)Explanation / Answer
1. a) Sarin affects the effectors of both autonomic and somatic nervous system. The somatic nervous system consists of the skeletal muscles whereas autonomic nervous system consistes of cardiac and smooth muscles. Sarin attacks the nervous system by attacking the degradation of neurotransmitter acetylcholine. There is over stimulated muscle contraction around heart and lungs and results in death. There is difficulty in breathing.
b) Sarin directly acts on acetylcholinesterase. Acetylcholine is responsible for the transmission of nerve impulse or signals. Sarin degrades the enzyme responsible for denaturing acetylcholine which is acetylcholinesterase. This happens at the synaptic cleft or neuromuscular junctions. When it degrades this enzyme the muscle is unable to relax and will attain overstimulated state.
c) In the presence of sarin smooth muscles and secretions go crazy. If neurotransmitters are used to convey information, the presence of sarin causes the neurotransmitters to continually convey information and cannot stop. Hence when eyes water in response to gas, it is unable to stop and keeps on watering. Same case with pupils too. Pupils keep on constricting.
d) The excess acetylcholine wil keep on stimulating cholinergic receptors causing the channels to be open and more receptive to the movement of sodium ions. Membrane will be depolarized and the signal will be continuous. It will keep on telling the sodium ions to move.
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