1. Muscular System

2. Types of Muscle ● Skeletal – striated & voluntary ● Smooth – involuntary ● Cardiac - heart The word “striated” means striped. Skeletal muscle appears striped under a microscope.

3. Role of Muscles in the Body Slide 6.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Produce movement  Maintain posture  Stabilize joints  Generate heat  Propel Substances

4. Muscles and Muscle Fiber Structure Muscles are composed of many fibers that are arranged in bundles called FASCICLES Individual muscles are separated by FASCIA, which also forms tendons Video on plantar fasciitis.

5. EPIMYSIUM = outermost layer, surrounds entire muscle. PERIMYSIUM = separates and surrounds fascicles (bundles of muscle fibers) ENDOMYSIUM = surrounds each individual muscle fiber This model of the muscles uses straws to represent fibers. Green = endomysium Yellow = perimysium Blue = epimysium

6. Muscle Layers

7. Epimysium Perimysium Endomysium

8. Sarcolemma = muscle fiber membrane Sarcoplasm = inner material surrounding fibers (like cytoplasm) Myofibrils = individual muscle fibers, made of myofilaments Muscles / Cells

9. Sarcolemma Mitochondrion Sarcoplasm Myofibril Nucleus

10. Myofibrils are made of ACTIN = thin filaments MYOSIN = thick filaments

11. Myofilaments ACTIN (thin) and MYOSIN (thick) -- form dark and light bands  A band = dArk thick (myosin)  I band = lIght thIn (actin)

15. It is important to remember the hierarchy fasicles myofibrils myofilaments actinmyosin

16. Muscle Contraction A skeletal muscles contraction begins at the neuromuscular junction. What do you think the definition of “neuromuscular junction” would be?

17. How Muscles Work with the Nervous System NEUROMUSCULAR JUNCTION - where a nerve and muscle fiber come together

18. 1. Neuron 2. Sarcolemma (or motor end plate) 3. Vesicle 4. Synapse 5. Mitochondria Motor Unit or Neuromuscular Junction

19. Neuromuscular Junction

20. The neurotransmitter that crosses the gap is ACETYLCHOLINE. This is what activates the muscle. Acetylcholine is stored in vesicles

22. Neuromuscular junction animation animation Focus Questions: What is the name of the stimulus that travels down the axon to the muscle fiber? An action potential Does the terminal (end) of the axon enter the muscle fiber? No. There is a gap between the two. Does acetylcholine enter the muscle fiber? No. What chemical does enter the muscle fiber, resulting in an action potential through the muscle fiber? Sodium

23. SLIDING FILAMENT THEORY (MODEL) The theory of how muscle contracts is the sliding filament theory. The contraction of a muscle occurs as the thin filament slide past the thick filaments. The sliding filament theory involves five different molecules and calcium ions. The five molecules are: myosin actin tropomyosin troponin ATP

26. ANIMATION OF SLIDING FILAMENT http://bigpictureeducation.com/animation-sliding-filament-theory

27. Sliding Filament theory Boat = Myosin (thick filament) Oar = Myosin side arm Water = Actin (thin filament) Life ring = Calcium

28. Resting 1.ATP is bound to myosin side arm. 2.ATP cleaves into ADP + P (high energy)

29. Step 1 Action potential 1.A nerve action potential releases acetylcholine into the synaptic cleft opening the Na+ channels. 2.Action potential spreads across sarcolemma releasing Ca into sarcoplasma

30. Step 2 Myosin-actin binding 1.Ca binds to troponin. 2.A shape change in troponin moves tropomyocin out of the way of actin binding site. 3.Actin and myosin bind using energy from cleaved ATP.

31. Step 3 Power Stroke 1.Side arm pivots so myosin and actin slide by each other shortening the sarcomere. 2.ADP and P released (low energy)

32. Step 4 ATP Binding Actin-myosin release 1.A different ATP molecule binds to active site. 2.Actin released

33. Step 5 ATP cleavage 1.Return to high energy state 2.Cycle will repeat if Ca still available.

34. Think it over The boat (myosin) does not move far in one cycle, can a muscle contraction occur with one cycle? No If a muscle is contracted what happens if a new molecule of ATP is not available? Muscle stays contracted- cramps Why does rigor mortis occur? (Hint: What chemical is no longer available to the body?) ATP is not available to control Ca release so contractions are continuous 6-8 hours after death. Body relaxes 16-24 hours as enzymes break down contractile structures.

35. Sarcomere summary

36. Sliding Filament Theory Focus questions: What happens to the length of the sarcomere during a contraction? The sarcomere shortens.

37. Sliding Filament Animation animation 2 Focus Questions: What chemical exposes the binding site for actin and myosin? Ca What is the source of energy for a contraction? ATP What is the name of the step in which the actin filament is actively contracted? Powerstroke What chemical must be present in order for the actin and myosin filaments to separate? ATP

38. Muscle contraction at the macroscopic level 1.Place your fingers along the angle of your jaw just in front of your ear. Grit your teeth and fell what happens to the hardness of the masseter muscle. During muscle contraction the muscle becomes ________________________.

39. 2.With your thumb and little finger of one hand, span the opposite arm’s bicep’s from the elbow to as close to the shoulder as possible. Bend the arm and observe the change in the length of the muscle. During muscle contraction the muscle ___________________ in length.

40. 3.Wrap a string around your extended upper arm and determine the circumference. Clench your fist tightly and flex your arm to contract the muscle. During muscle contraction the diameter of the muscle _____________________.

41. Energy Source -ATP is produced by CELLULAR RESPIRATION which occurs in the mitochondria -Creatine phosphate increases regeneration of ATP * Only 25% of energy produced during cellular respiration is used in metabolic processes - the rest is in the form of HEAT. -maintains body temperature.

42. Why might products like pro-creatine claim to increase energy? ATP = adenosine triphosphate ADP = adenosine diphosphate

43. Other Terms ● 1. Threshold Stimulus ● 2. All-or-None Response ● 3. Motor Unit ● 5. Recruitment ● 6. Muscle Tone ● 7. Muscular Hypertrophy ● 8. Muscular Atrophy ● 9. Muscle Fatigue ● 10. Muscle Cramp ● 11. Oxygen Debt

44. 1. Threshold Stimulus Minimal strength required to cause a contraction Motor neuron releases enough acetylcholine to reach threshold 2. All-or-None Response Fibers do not contract partially, they either do or don't

45. 3. Motor Unit The muscle fiber + the motor neuron 4. Recruitment more and more fibers contract as the intensity of the stimulus increases 5. Muscle Tone Sustained contraction of individual fibers, even when muscle is at rest

46. 6. Hypertrophy - muscles enlarge (working out or certain disorders) 7. Atrophy - muscles become small and weak due to disuse

47. 8. Muscle Fatigue - muscle loses ability to contract after prolonged exercise or strain 9. Muscle Cramp - a sustained involuntary contraction 10. Oxygen Debt - oxygen is used to create ATP, -- not have enough oxygen causes Lactic Acid to accumulate in the muscles → Soreness *See Magic School Bus

48. 11. Origin and Insertion Origin = the immovable end of the muscle Insertion = the movable end of the muscle The biceps brachii has two origins (or two heads).

49. What is rigor mortis? A few hours after a person or animal dies, the joints of the body stiffen and become locked in place. This stiffening is called rigor mortis. Depending on temperature and other conditions, rigor mortis lasts approximately 72 hours. The phenomenon is caused by the skeletal muscles partially contracting. The muscles are unable to relax, so the joints become fixed in place.

50. What is tetanus? Tetanus causes cholinosterase to not break down the acetylcholine in the synapse. This results in a person's muscles contracting and not relaxing. A tetanus shot must be administered shortly after exposure to the bacteria. Once you develop tetanus, there is no cure.