The document summarizes the key components and functions of the three main types of muscles - skeletal, smooth, and cardiac muscles. It describes the structure of skeletal muscles including tendons, fascia, muscle fibers, and myofibrils. It then explains the process of skeletal muscle contraction which is initiated by a nerve impulse and involves the release of calcium ions, cross-bridging of actin and myosin filaments, and the use of ATP for energy. The document also briefly discusses smooth and cardiac muscle as well as muscle fatigue, hypertrophy, and diseases like muscular dystrophy.

1. CHAPTER 8: MUSCULAR SYSTEM

2. 3 Types of Muscles 1. Skeletal 2. Smooth 3. cardiac

3. bone tendon fascia muscle fiber myofibril filaments Structure of a Skeletal Muscle muscle fascicle

4. 1. Tendon – holds the muscle to the bone

5. 2. Fascia - connective tissue that covers and separates muscles

6. 3. Muscle fiber = the muscle cell

7. 4. Myofibril – the contractile fibers in a muscle fiber

8. 2 Types a) actin - thin b) myosin - thick 5. Filaments

9. Muscle Fiber Structure

10. 1. Sarcoplasmic Reticulum - tubes run parallel to the myofibrils - stores calcium & functions as the ER

11. 2. Transverse Tubules - run at right angles to myofibrils - activate muscle contraction when stimulated

12. 3. Sarcolemma - the “cell membrane”

13. Myofibril Structure

14. Neuromuscular Junction - place where nerve fiber & muscle fiber meet

15. - each muscle fiber is connected to a motor neuron - nerve fiber meets at the motor end plate

16. - end of motor neurons contains synaptic vesicles that have neurotransmitters in them - one motor neuron can control many muscle fibers  motor unit

17. The myogram

18. Skeletal Muscle Contraction  a specific sequence of events needs to occur in order for a muscle fiber to contract - it starts with a nerve impulse traveling down a motor neuron axon - the nerve impulse causes the synaptic vesicles to release the neurotransmitter ACh - the ACh attaches to ACh receptors on sarcolemma then is broken down by acetylcholinesterase Neurotransmitter release

19. - the nerve impulse travels through the muscle fiber which causes the sarcoplasmic reticulum to release Ca 2+ ions - the calcium attaches to the troponin protein which will then move the tropomyosin proteins to uncover the active site on the actin

20. - the myosin heads attach to the active site on the actin filament - ATP is used, and the myosin pulls on the actin by the myosin cross-bridges - the muscle shortens as a contraction occurs Muscle contraction - the muscle will stay contracted until the Ca 2+ is reabsorbed by the SR - the active site will be covered up - actin slides back into its original position Muscle contraction 1

22. Energy Sources for Contraction - ATP supplies the energy - ADP needs to be regenerated into ATP - can borrow a phosphate from creatine phosphate - regenerate through the process of cell respiration

24. - myoglobin - can store O 2 in muscles for cell respiration - if O 2 levels are low and oxygen debt occurs glucose  pyruvic acid  lactic acid  cramps

25. - can lead to muscle fatigue  muscle loses ability to contract

26. Muscular Response Threshold Stimulus - minimal strength needed to start a contraction All - or - None Response - a muscle fiber will contract or it will not - no partial contractions Recruitment - the greater the stimulus, the more motor units will be activated, more muscle fibers will contract

27. The myogram latent period contraction period relaxation period recovery period

28. latent period - time between stimulus and contraction contraction period - time for the muscle to contract relaxation period - actin slides back into place recovery period - O 2 resupplied to muscles

29. Muscular hypertrophy - muscles get larger due to increased use Muscular atrophy - muscles get smaller due to less use

30. Smooth Muscle - thin - contains actin and myosin - are randomly arranged  no striations 2 Types a) Multiunit - found in eye and blood vessels - contracts only after receives a nerve impulse

31. b) Visceral - found in internal organs - displays rhythmic patterns - muscles able to stimulate each other - no continuous stimulus needed - Contraction is almost the same as in skeletal muscles - besides ACh, can be stimulated by norepinephrin - contraction occurs more slowly - muscles are able to stretch

32. Cardiac Muscles - only found in the heart - has actin and myosin - contains many mitochondria

33. Muscular Dystrophy  caused by a defective gene  the muscle fibers are unusually susceptible to damage  muscles become weaker and may be replaced by fat and connective tissue  there are over 40 types of MD  there is no cure

35. Anabolic Steroids Anabolic steroids change muscle mass and strength by three processes. 1. Increases the production of proteins 2. Blocks the hormone cortisol , which decreases muscle breakdown 3. Leads cells to differentiate into muscle more readily than fat