UNIT 7 Muscles and Muscle Tissue Chapter 9

1. UNIT 7 Muscles and Muscle Tissue (Chapter 9) Skeletal Muscle Physiology II Effects of Exercise on Muscle Muscle Disorders (8th edition)

2. Types of Skeletal Muscle Fibers skeletal muscle fibers are categorized according to:   how they manufacture energy (ATP) - aerobic vs. anaerobic how quickly they contract skeletal muscle fibers are divided into three classes (table 9.2): SLOW OXIDATIVE fibers FAST GLYCOLYTIC fibers FAST OXIDATIVE fibers (8th edition)

3. slow oxidative fibers dark red color due to abundant myoglobin obtain energy from aerobic metabolic reactions (oxygen dependent) contain a large number of mitochondria rich supply of capillaries contract slowly and resistant to fatigue (8th edition)

4. fast glycolytic fibers contain little myoglobin (white in color) and few mitochondria about twice the diameter of slow-oxidative fibers contain more myofilaments and generate more power depend on anaerobic pathways (not oxygen dependent) contract rapidly and tire quickly (8th edition)

5. fast oxidative fibers have an intermediate diameter contract quickly like fast glycolytic fibers are oxygen-dependent (aerobic) have high myoglobin content (red color) and rich supply of capillaries somewhat fatigue-resistant more powerful than slow oxidative fibers *skeletal muscles typically have all 3 types of fibers, but vary in the amount of each fiber; athletes can actually alter the composition of their muscles based on the activities that they do; for example, marathon runners develop their slow oxidative fibers, whereas weight lifters develop their fast glycolytic fibers. (8th edition)

6. Muscle Metabolism immediate energy - used in first 10-30 seconds of vigorous exercise; ATP creatine phosphate (ATP-CP) system used; creatine phosphate contributes a phosphate to ADP to make ATP; 1 creatine phosphate (CP) = 1 ATP; all 3 skeletal fiber types use this system short-term energy - used approx. 30 - 90 seconds into vigorous exercise; uses glycolysis to break down glucose to pyruvate to lactate (lactic acid); 1 glucose = 2 ATP; used by fast glycolytic fibers long-term energy - used approx after 2 min of vigorous exercise; uses glycolysis, citric acid cycle (kreb’s cycle), and electron transport chain to fully oxidize glucose; 1 glucose = 36 ATP (max); used by slow oxidative fibers and fast oxidative fibers (8th edition)

7. Comparison of the 3 Types of Muscle Tissue (Table 9.3) SKELETAL MUSCLE characteristics: striated multinucleated under the control of the voluntary (somatic) nervous system contains myofibrils composed of sarcomeres (gives it the striated appearance) contains T tubules no gap junctions well developed sarcoplasmic reticulum fast contracting every fiber is controlled by a nerve (8th edition)

8. Comparison of the 3 Types of Muscle Tissue (Table 9.3) CARDIAC MUSCLE characteristics: striated and branched uni- or binucleate contains intercalated discs under the control of the involuntary (autonomic) nervous system = ANS contains myofibrils composed of sarcomeres (gives it the striated appearance) contains T tubules presence of gap junctions at the intercalated discs less developed sarcoplasmic reticulum than skeletal muscle found in the wall of the heart only not every fiber is controlled by a nerve; can contract without input from the nervous system (8th edition)

9. Comparison of the 3 Types of Muscle Tissue (Table 9.3) SMOOTH MUSCLE characteristics: unstriated and with a fusiform shape uninucleate under the control of the involuntary (autonomic) nervous system = ANS does not contain myofibrils composed of sarcomeres does not contain T tubules presence of gap junctions less developed sarcoplasmic reticulum than skeletal muscle found in the walls of hollow organs not every fiber is controlled by a nerve; can contract without input from the nervous system (8th edition)

10. Exercise (8th edition)

11. Effects of Exercise on Muscles - Resistance Training (“Weights”) (8th edition)

12. Effects of Exercise on Muscles - Resistance Training (“Weights”) Increase in muscle strength occurs because of neural adaptations and muscle hypertrophy (increase in muscle size) Neural Adaptations - occur in the first 4 weeks of weight training; hypertrophy generally does not occur in the first 4 weeks of lifting weights recruitment of more muscle fibers more inhibition of the antagonistic muscles reduced inhibition by the golgi tendon organ - the golgi tendon organ senses tension, and responds by stimulating the relaxation of the muscle to prevent injury; arm wrestlers train themselves in a way that minimizes the effects of the golgi tendon organs (8th edition)

13. Effects of Exercise on Muscles - Resistance Training (“Weights”) Muscle Hypertrophy - starts to occur after 4 weeks of training not due to increase in number of muscle fibers (cells) it is due to increase in the number of myofibrils in the muscle cell; muscle cell becomes thicker in diameter Myth: “delayed onset muscle soreness (sorness for the next few days) is due to lactic acid buildup” -- FALSE! it is really due to muscle damage (to the sarcolemma and interior of the cell) (8th edition)

14. Flexibility (8th edition)

15. Flexibility Training flexibility - range of motion around a joint or group of joints flexibility training decreases the risk of injury and can possibly enhance recuperation time and performance Limbering - “warming up”; not the same as stretching; restores the normal flexibility (what you are presently capable of) of the muscles and tendons; no change in range of motion has been gained; limbering is important prior to exercise for prevention of injuries Stretching - leads to actual lengthening of the muscle fibers, and likewise, lengthening of proprioceptors (e.g. muscle spindles) which detecting stretch in the muscle or tendon; stretching over long periods of time can lead to a greater range of motion around a joint or group of joints; this often requires assistance from a partner who provides some resistance in order to obtain optimal results (8th edition)

16. Nutritional Supplements (8th edition)

17. Nutritional Supplements protein powers, muscle builders, and bars -- some athletes may require additional protein above their normal diet; however, beware! many supplements may be spiked with ephedrine or anabolic steroids -- the supplement industry is not regulated! (you don’t always know exactly what you are taking) gatorade - studies show increased hydration vs. drinking water; because it tastes good, you will drink more of it; however, it contains a lot of sugar and calories! creatine - some athletes take creatine to improve performance; the idea is that the more creatine in the body, the more of the immediate energy source available (recall that creatine phosphate is used during the first 10-30 seconds of vigorous exercise); however, there is little evidence that creatine is beneficial for the average person (8th edition)

18. Anabolic Steroids can create increased muscle hypertropy and strength; however, many side effects are associated with steroids; these include small testes (and decreased fertility), increased estrogen (men can develop breasts), prostate gland hypertrophy, increased LDL (bad ones), decreased HDL (good ones), increased heart attack risk, and liver damage (8th edition)

19. Caffeine the most widely consumed drug in the world! it is used to increase mental awareness and decrease fatigue; however, you can build up a tolerance to caffeine if it used too frequently (8th edition)

20. Physical and Mechanical Aids - e.g. use of a weight lifting belt or knee brace; application of massage (8th edition)

21. Psychological e.g. use of visualization; visualizing yourself performing the exercise or event (sports) before it actually occurs; this technique has been shown to be highly effective (8th edition)

22. Disorders of Muscle Tissue - muscle tissues experience few disorders; heart muscle is the exception; skeletal muscle is remarkably resistant to infection Muscular Dystrophy – a group of inherited muscle destroying diseases; affected muscles enlarge with fat and connective tissue and muscles degenerate (8th edition)

23. Disorders of Muscle Tissue - muscle tissues experience few disorders; heart muscle is the exception; skeletal muscle is remarkably resistant to infection Strain - tearing of a muscle; also known as a muscle “pull” (you learned about a “sprain” in Unit 6; how is a strain different from a sprain?) (8th edition)

24. This concludes the current lecture topic (close the current window to exit the PowerPoint and return to the Unit 7 Startpage) (8th edition)