1. Physiological Factors Affecting Testing By Prof. Dr. Samy A. Nasef

2. Muscle Tissue One of 4 primary tissue types, divided into: skeletal muscle cardiac muscle smooth muscle Without these muscles, nothing in the body would move and no body movement would occur

3. 6 Functions of Skeletal Muscles 1.Produce skeletal movement 2.Maintain body position and posture 3.Support soft tissues 4.Guard body openings (entrance/exit) 5.Maintain body temperature 6.Store Nutrient reserves

4. Organization of Connective Tissues Muscles have 3 layers of connective tissues: 1. Epimysium-Exterior collagen layer Connected to deep fascia Separates muscle from surrounding tissue 2. perimysium- Surrounds muscle fiber bundles (fascicles) Contains blood vessel and nerve supply to fascicles 3. endomysium

5. 3. Endomysium Surrounds individual muscle cells (muscle fibers) Contains capillaries and nerve fibers contacting muscle cells Contains satellite cells (stem cells) that repair damage

6. Muscle Attachments Endomysium, perimysium, and epimysium come together: at ends of muscles to form connective tissue attachment to bone matrix i.e., tendon (bundle) or aponeurosis (sheet)

7. What are the characteristics of skeletal muscle fibers? Skeletal muscle cells are called fibers Figure 10–2 اسرة صوتك سنتر فاروس

8. Skeletal Muscle Fibers Are very long Develop through fusion of mesodermal cells (myoblasts- embryonic cells)) Become very large Contain hundreds of nuclei –multinucleate Unfused cells are satellite cells- assist in repair after injury

9. The Sarcolemma The cell membrane of a muscle cell Surrounds the sarcoplasm (cytoplasm of muscle fiber) A change in transmembrane potential begins contractions All regions of the cell must contract simultaneously

10. Transverse Tubules (T tubules) Transmit action potential – impulses through cell Allow entire muscle fiber to contract simultaneously Have same properties as sarcolemma Filled with extracellular fluid

11. Myofibrils- 1-2um in diameter Lengthwise subdivisions within muscle fiber Made up of bundles of protein filaments (myofilaments) Myofilaments - are responsible for muscle contraction 2 Types of Myofilaments Thin filaments: made of the protein actin Thick filaments: made of the protein myosin

12. Sarcoplasmic Reticulum (SR) A membranous structure surrounding each myofibril Helps transmit action potential to myofibril Similar in structure to smooth endoplasmic reticulum Forms chambers (terminal cisternae) attached to T tubules اسرة صوتك سنتر فاروس

13. A Triad Is formed by 1 T tubule and 2 terminal cisterna Cisternae Concentrate Ca 2+ (via ion pumps) Release Ca 2+ into sarcomeres to begin muscle contraction اسرة صوتك سنتر فاروس

14. Structural components of the Sarcomeres Figure 10–4 -The contractile units of muscle -Structural units of myofibrils -Form visible patterns within myofibrils اسرة صوتك سنتر فاروس

15. InterActive Physiology: Contraction of Whole Muscle PLAY Tension Produced by Whole Skeletal Muscles Depends on: internal tension produced by muscle fibers external tension exerted by muscle fibers on elastic extracellular fibers total number of muscle fibers stimulated

16. Motor Units in a Skeletal Muscle Figure 10–17

17. Motor Units in a Skeletal Muscle Contain hundreds of muscle fibers That contract at the same time Controlled by a single motor neuron InterActive Physiology: Contraction of Motor Units PLAY

18. Recruitment (Multiple Motor Unit Summation) In a whole muscle or group of muscles, smooth motion and increasing tension is produced by slowly increasing size or number of motor units stimulated

19. Maximum Tension Achieved when all motor units reach tetanus Can be sustained only a very short time Sustained Tension Less than maximum tension Allows motor units to rest in rotation