lecture_notes_17_(ta)

lecture_notes_17_(ta) - ( TA NOTES IN RED ) Lecture 17:...

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( TA NOTES IN RED ) Lecture 17: Muscle Physiology Reading: chapter 8, section: skeletal muscle, pgs 272-279; 285-294 (pgs 277-283; 288-297, if using 5 th edition) Muscle Metabolism - ATP ( THE UNIVERSAL ENERGY CURRENCY ” ) is required as an energy source to drive two processes underlying muscular contraction and relaxation: the power stroke of the contractile apparatus and the active transport of Ca ++ into the sarcoplasmic reticulum. The ATP made available for these processes is derived from 3 metabolic sources (Figure 8-22) : ( 1 ) Creatine Phosphate - this compound provides a ( PRIMARY ) reserve of high-energy phosphate that is utilized to synthesize ATP. It is the first source of ATP that is utilized by skeletal muscle cells when they contract. It is generated by the reversible enzymatic reaction utilizing creatine kinase : creatine kinase creatine phosphate + ADP <-- creatine + ATP ( THIS PROCESS IS REVERSIBLE . E NERGY CAN BE STORED AS CREATINE PHOSPHATE . D URING PERIODS OF REST , ATP CAN BE CONVERTED INTO CREATINE PHOSPHATE . D URING PERIODS OF HIGH ENERGY DEMAND , THE CREATINE PHOSPHATE CAN BE CONVERTED BACK TO ATP) During periods of muscular rest, excess ATP, generated by glycolysis and oxidative phosphorylation, is converted to creatine phosphate that is stored by the muscle cells as an energy reserve. ( 2 ) Oxidative Phosphorylation ( OXYGEN REQUIRED ) - this metabolic reaction sequence takes place when sufficient oxygen is present, and can be fueled by glucose or fatty acids derived from glycogen or fat reserves, respectively. Muscle activity that is supported by this form of metabolism is referred to as aerobic because it requires oxygen. Some skeletal muscle cells have an abundance of an oxygen binding protein called myoglobin that facilitates the transport of oxygen from the blood. ( AND MAKES THE MUSCLE RED ) ( 3 ) Glycolysis - this rapid metabolic reaction sequence continues to operate when there is insufficient oxygen available from the bloodstream to sustain oxidative phosphorylation. It utilizes glucose to generate 2 ATPs and 2 molecules of pyruvic acid. Muscle activity that is supported by this form of metabolism is referred to as anaerobic because it does not require oxygen. The excess pyruvic acid is converted to lactic acid that is removed by the bloodstream. ( LACTIC ACID CAN CAUSE MUSCLE PAIN AND FATIGUE ) ( SEE FIGURE 8.23 FOR THE BIOCHEMICAL CASCADE )
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Fatigue ( FATIGUE IS THE INABILITY OF MUSCLES TO MAINTAIN TENSION ) - during periods of intense exercise muscle tension is sometimes unable to be maintained. This can result from ( 1 ) muscle fatigue when the muscle cells are 1) unable to synthesize sufficient quantities of ATP to maintain contractile activity, or 2) accumulate too much lactic acid from glycolysis (which may inhibit
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This note was uploaded on 05/02/2008 for the course NPB 101 taught by Professor Fuller,charles/goldberg,jack during the Winter '08 term at UC Davis.

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lecture_notes_17_(ta) - ( TA NOTES IN RED ) Lecture 17:...

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