1. Muscles

2. Skeletal muscle Cross- SectionLongitudinal

3. Smooth Muscle Cross- Section longitudinal

4. Muscle Tissue Components tendon - connects skeletal muscle to bone epimysium - fibrous connective tissue around belly of skeletal muscle fasiculi - bundles of muscle fibers perimysium - connective tissue surrounding fasiculi endomysium - connective tissue surrounding the individual muscle fibers (muscle cell)

5. Muscle components muscle fiber - single muscle cell (threadlike in shape) sarcolemma - membrane surrounding the muscle fiber sarcoplasm - specialized cytoplasm of muscle fiber containing multiple nuclei and mitochondria myofibrils - "rod-like" structures running through the muscle fibers that contain actin and myosin make muscle appear striated

6. Muscle types Myosins are protein motors. Upon interaction with actin filaments, they utilize energy from ATP hydrolysis to generate mechanical force. Muscles are typed based upon the types of myosin protein fibers present there are different forms of the muscle myosins –TYPE I (Slow Twitch) –Type IIa/IIx (Fast Twitch)

7. Muscle types Are determined both genetically & functionally based upon how fast they can produce a contractile twitch every muscle composed of varying % composition of two types

8. TYPE I - SLOW TWITCH Tonic muscles (red) - Leg muscles TYPE II - (IIa & IIx) FAST TWITCH Tetanic muscles (white) - Pectoral muscles slower contraction times (100-110 msec) faster contraction times (50 msec) contain myoglobin (red)no myoglobin (white) continuous use muscles - prolonged performancefor endurance performance ( marathoners) one time use muscles - brief performances for power & speed (sprinters) marathoner: 80% type I & 20% type II sprinter: 20% type I & 80% type II best in long slow sustained contractions best in rapid (short) contractions not easily fatiguedeasily fatigued more capillary beds, greater VO 2 max less capillary beds smaller in sizelarger in size lower glycogen contenthigher glycogen content poor anaerobic glycolysis * predominantly anaerobic glycolysis easily converts glycogen to lactate wo O 2 higher fat contentlower fat content poorly formed sarcoplasmic reticulumwell formed sacroplasmic reticulum

9. Distribution of slow/fast twitch fibers Relative Distributions of Slow Twitch & Fact Twitch Myosin forms (Type I & Type II) Type I (slow) Type II (fast)Type IIaType IIx Average person 50% 40% 10% spinal injury4%96%48% sprinter20%80%45%35% couch potato 40%60%30% marathoner80%20% 0%

10. MUSCLES CONTRACT!!! Muscles can not push, they may only CONTRACT (pull) A muscle contraction is called a muscle TWITCH

11. The sarcomere basic repeat unit of striated muscle, delimited by Z-lines

12. sarcomere SARCOMERE REGIONS I band - "clear zone" around Z-line A band - "dark region" in center of sarcomere M line - mid point of the sarcomere H zone - "clear zone" in the center of sarcomere around M line

13. Sliding Filament Theory A band remains constant in its size dimensions H Zone becomes denser I band varies in length becoming shorter & disappearing

14. 4 parts of a Muscle twitch 1) latent period – –5 msec time between application of Action Potential & initiation of contraction 2) contraction – (slow twitch) –40 msec muscle shortens & does its work 3) relaxation – –50 msec muscle elongates & returns to original position 4) refractory period – –2 msec time of recovery between stimulations of muscle

15. Muscle contraction cycle Step 1 –Arrival of the action potential Action potential causes AcH to be released. ACH binds to receptors on sarcolemma Receptors open, causing Na+ to flood in changing membrane potential.

16. Muscle contraction #2

17. Muscle contraction #3 Step 3 –Release of Calcium

18. Muscle Contraction #4 Step 4: –calcium changes tropomyosin shape –Exposes myosin binding sites on actin

19. Muscle contraction #5 #5 –ATP binds to cross bridge Myosin head changes shape releases from actin –ATP hydrolyzes Head is in high energy configuration –Head binds to actin –ADP+P are released from myosin Head moves actin towards center

20. Types of contractions

21. DOMS Occurs usually at the beginning of a new training program. –Characterized by stiffness, soreness –More often occur after activities with eccentric contractions. –causing damage to the muscle cell membrane, which sets off an inflammatory response. –This inflammatory response leads to the formation of metabolic waste products, –These chemicals stimulate pain nerves and attract neutrophils (a type of white blood cell) to the site of injury. –There, neutrophils generate free radicals (molecules with unshared electrons), which also damage the cell membrane. –Swelling is also common, and can lead to pain.

22. Effect of exercise on muscle Eccentric contractions produce muscle hypertrophy –Eccentric contractions put your muscle fibers under a great deal of tension causing microtears and severe DOMS. –if you can induce muscle fiber injury, satellite cells are activated. Satellite cells are myogenic stem cells which regenerate muscle. Satellite cells proliferate (undergo mitosis) and give rise to new immature muscle cells. These new cells fuse with an existing muscle fiber causing that fiber to get bigger (i.e., hypertrophy)

23. Maintaining muscle over time Muscle strength in people increases until the early 20’s –It remains fairly stable until about 50 in untrained people –Loss of maximal strength is due to atrophy of type II fibers. –People of any age can show strength gains through regular strength training

24. Strength training benefits for women Enhanced bone modeling to increase bone strength and reduce the risk of osteoporosis Stronger connective tissues to increase joint stability and help prevent injury Increased functional strength for sports and daily activity Increased lean body mass and decreased nonfunctional body fat Higher metabolic rate because of an increase in muscle and a decrease in fat Improved self-esteem and confidence Some factors may reduce these benefits including –including the exclusive use of weight training machines, training with loads that are too light, and not progressing in resistance or intensity.