1. The Muscular System

2. 3 Types of Muscles

3. A Muscle is Composed of a Variety Of Tissues

4. Sarcomere – the structural and functional unit of a myofibril

5. The Sarcomere Thin and Thick Filaments

7. Muscular Responses Twitch – a brief period of contraction followed by a period of relaxation Phases 1. Latent Period – muscle tension is beginning 2. Period of Contraction Muscle fibers shortening 3. Period of Relaxation Ca 2+ renters the sarcoplasmic reticulum Relaxation – 1.acetylcholinesterase decomposes ACh in the synapse 2. Ca 2+ pump quickly moves Ca 2+ back into sarcoplasmic reticulum

8. Figure 9.14b Latent period Extraocular muscle (lateral rectus) Gastrocnemius Soleus Single stimulus (b) Comparison of the relative duration of twitch responses of three muscles

10. Summation – The force of individual twitches combines Incomplete tetanus – Ca 2+ increases in sarcoplasm results in quivering response Complete Tetanus – no period of relaxation

11. Treppe

12. The force that a muscle can generate is dependent on the length that it is stretched before stimulation

13. Muscle Fiber Type

14. The force that a muscle develops depends on: 1.The frequency at which individual muscle fibers are stimulated 2.How many fibers take part in the overall contraction - RECRUITMENT

15. Types of Contractions Isotonic Contraction – muscle changes length and moves a load – Concentric contraction – a muscle shortening contraction – Eccentric contraction – a muscle lengthening contraction Isometric contraction – tension in muscle increases but the muscle does not lengthen or shorten

16. Muscle Fatigue Exercise for a long period of time may cause a muscle to lose the ability to contract - FATIGUE Why? 1. decreased blood flow 2. ion imbalances across sarcolemma from repeated stimulation 3. psychological loss of the desire to exercise 4. increase in lactic acid = lowered pH which prevents muscles from responding to stimulation

17. What is a Cramp? A sustained, painful, involuntary muscle contraction Result from decreased electrolyte concentration in extracellular fluid which triggers uncontrolled muscle stimulation

18. Sliding Filament Theory http://www.blackwellpublishing.com/matthe ws/myosin.html http://www.blackwellpublishing.com/matthe ws/myosin.html http://www.mhhe.com/biosci/esp/2002_genera l/Esp/folder_structure/su/m4/s11/sum4s11_9.htm