chapt11im

chapt11im - CHAPTER 11: MUSCULAR TISSUE Chapter Overview...

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45 CHAPTER 11: MUSCULAR TISSUE Chapter Overview Introduction Chapter 11 is concerned with the mechanisms by which muscle cells contract. The author begins the presentation with the characteristics of muscle cells in general and then the microscopic characterization of skeletal muscles. Skeletal muscles contract when an action potential is initiated and the sarcolemma’s voltage-gated channels open. The stimulus for this is acetylcholine produced by motor neurons. Next, the sarcoplasmic reticulum becomes permeable to calcium ions. Contraction is made possible when calcium ions have been released. In turn, relaxation is only possible when the calcium ions have been actively transported back into the sarcoplasmic reticulum. Understanding calcium movements is the key to understanding the causes of muscular dystrophy and rigor mortis. The author then moves on to the actions of whole muscles and muscle metabolism. Finally, Saladin briefly elucidates the microscopic anatomy, innervation, and contraction mechanisms of cardiac and smooth muscles. Key Concepts Here are some concepts that students should have a better understanding of after reading this chapter: general characteristics of all muscle tissues; the series-elastic components; microscopic arrangement and roles of the myofilaments and the regulatory proteins; function and microstructure of the neuromuscular junction; the establishment of and changes in membrane potential as they relate to excitation; the sarcoplasmic reticulum as a calcium reservoir; the sequence of events leading up to myosin binding to actin and the execution of the power stroke; the activities preceding relaxation: cessation of acetylcholine release, the breakdown of acetylcholine, and uptake of calcium ions; muscle tone and length-tension; the behaviors of whole muscle, recruitment, threshold, latency, and tetany; the differences between isometric and isotonic contractions; importance of and sources of chemical energy; clarify fatigue, lactic acid build-up, and oxygen debt; distinguish between the physiologies of fast and slow twitch fibers; changes in muscles related to exercise; cardiac muscle structure, contraction, and metabolism; the innervations (if any), types, contraction, and microscopic structures of smooth muscle as compared to skeletal and cardiac muscles; and the causes of muscular dystrophy and myesthenia gravis. Topics for Discussion 1. Have the students compare the action of curare (binds to acetylcholine receptors and formerly given pre-surgically as a muscle relaxant) to that of botulinum toxin. Why do those plants in South America possess curare? Insects are the major herbivores in the tropical forest. The plants that contain curare or other poisons useful against insect nervous systems would have a useful defense against herbivores. 2.
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This note was uploaded on 02/09/2012 for the course BIO 102 taught by Professor William during the Spring '11 term at Harvard.

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chapt11im - CHAPTER 11: MUSCULAR TISSUE Chapter Overview...

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