lhatomy. neurotransmitters and receptors of the sormatic motor, sympathetic, and
ID: 178668 • Letter: L
Question
lhatomy. neurotransmitters and receptors of the sormatic motor, sympathetic, and parasympathetic divisions. 17. Nicotinic cholinergic receptors are called nicotinic because nicotine can bind to 2 those receptors. Therefore, nicotine is an agonist to acetylcholine. A non-smoker who chews nicotine-containing gum might notice an increase in heart rate, a function that is controlled by sympathetic neurons. However, postganglionic sympathetic neurons secrete norepinephrine, not acetyleholine. then can nicotine affect heart rate? Compare and contrast the anatomy and chemical communication of the sympathetic and parasympathetic branches. Compare the anatomy. neurotransmitters and receptors of the somatic motor, sympathetic, and parasympathetic divisions. Chapter 12: Muscles 18. Which of the following would prevent the continuation of a contraction of a skeletal/cardiac/smooth muscle cell? Check all that apply o acetylcholine binds to cholinergic receptors o norepinephrine binds to adrenergic receptors o a lack of ATP o tropomyosin pulls away from the myosin-binding site on actin o the activity of the myosin light chain (MLC) Phosphatase is higher than the activity of the MLC Kinase o calcium ions are pumped into the sarcoplasmic reticulumExplanation / Answer
Adrenaline and norepinephrine act as part of signaling pathway and aids in furnishing the task of muscle contraction. Their binding to the receptor does not prevent muscle contraction.
ATP is crucial to muscle contraction as it disrupts the myosin-actin cross bridge and causes the muscle to proceed contraction process. So, lack of ATP prevents muscle contraction.
Tropomyosin if pulls away from myosin binding site on actin then muscle contraction will proceed. Actually, binding of tropomyosin binds with troponin which itself has the binding site on actin restricts the binding of actin with myosin and thus prevent a contraction from proceeding.
The higher activity of MLC phosphatase than Kinase lead to dephosphorylate myosin light chain which is normally phosphorylated by MLC kinase and thus prevent muscle contraction.
Calcium ions are important to start the contraction process because of calcium influx in important inside the cell either through the sarcoplasmic reticulum or through the extracellular matrix. Further calcium ion bind to the calmodulin which in turn activates MLC kinase to phosphorylate the myosin light chain. Thus calcium ion pumping inside the sarcoplasmic reticulum hardly prevent the muscle contraction because the ion influx is possible through extracellular matrix as well. Moreover, once the muscle contraction started pumping of calcium ion could not prevent it. For preventing contraction whole process will have to be reversed by MLC phosphatase.
Hence, the answers should be
1) lack of ATP
2) the activity of MLC phosphatase is higher than that of MLC kinase
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