chapter_10_V2U6acb.pptx POWER POINT PRESENTATION ON MUSCLE AND MUSCLE TISSUE

POWER POINT PRESENTATION ON MUSCLE AND MUSCLE TISSUE

1. Muscles and Muscle Tissue Raritan Valley Community College Dr. Ahmed Katsha [email protected]

2. Disclosure This course is using Open Education Resources (OER) mainly from OpenStax . This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax , Rice University and any changes must be noted. Images in these slides are from OpenStax textbook unless otherwise noted. Text is a mix from OpenStax text and Dr. Ahmed Katsha own explanation.

3. Learning Objects Explain the organization of muscle tissue Describe the function and structure of skeletal, cardiac muscle, and smooth muscle Explain how muscles work with tendons to move the body Describe how muscles contract and relax Define the process of muscle metabolism Explain how the nervous system controls muscle tension Relate the connections between exercise and muscle performance Explain the development and regeneration of muscle tissue

4. Why This Matters Understanding skeletal muscle tissue helps you to treat strained muscles effectively with RICE (rest, ice, compression and elevation)

5. Group Discussion How many types of muscles are there? How can you distinguish between each one? What are the functions of muscles? Describe the connective tissue surrounds muscles. Summarize the events at the neuromuscular junction. Summarize the events that lead to muscle contraction.

6. Videos Muscles https://www.youtube.com/watch?v=Ktv-CaOt6UQ https://www.youtube.com/watch?v=FfFBoIkdDgQ https://www.youtube.com/watch?v=jqy0i1KXUO4 Contraction https://www.youtube.com/watch?v=I80Xx7pA9hQ Structure of skeletal muscle https://www.youtube.com/watch?v=fEgjXKvO6A4 https://www.youtube.com/watch?v=hHoaiD_4DW8 Smooth Muscle https://www.youtube.com/watch?v=3JJV47xz6ls Cardiac muscle https://www.youtube.com/watch?v=iP1H-VS2hl8

7. Overview of Muscle Tissue The body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Easy Concepts

8. Features of Muscle Tissue Excitability: plasma membranes can change their electrical states (from polarized to depolarized) and send an electrical wave called an action potential along the entire length of the membrane. Elasticity: a muscle can return to its original length when relaxed due to elastic fibers. Extensibility: it can stretch or extend. Contractility: allows muscle tissue to pull on its attachment points and shorten with force. Easy Concepts

9. Cardiac muscle Found only in heart Fibers each have one to two nuclei Striated Involuntary: cannot be controlled consciously They have a special junction called intercalated discs. They provide strong attachment between the cardiac muscle cells. They are branched cells. Types of Muscle Tissue Easy Concepts

10. Skeletal muscle Multinucleated organs attached to bones and skin Skeletal muscle fibers are elongated and striated. Voluntary muscle: can be consciously controlled Types of Muscle Tissue Easy Concepts

11. Smooth muscle Found in walls of hollow organs like stomach, urinary bladder, and airways Spindle shaped and not striated Involuntary: cannot be controlled consciously Can contract on its own without nervous system stimulation Types of Muscle Tissue Easy Concepts

12. Four important functions Produce movement: responsible for all locomotion and manipulation like walking, digesting, and pumping blood Maintain posture and body position Stabilize joints Generate heat as they contract Additional functions Protect organs, form valves, control pupil size, cause “goosebumps” Muscle Functions Easy Concepts

13. Each skeletal muscle has three layers of connective tissue that enclose it and provide structure to the muscle as a whole. Epimysium: a sheath of dense, irregular connective tissue. allows a muscle to contract and separates muscle from surrounding tissues and organs. Perimysium: middle layer of connective tissue surrounding the fascicle. Fascicle: Bundle of muscle fibers grouped together within perimysium. Endomysium: A thin connective tissue layer of collagen and reticular fibers surrounding each muscle fiber/cell. Skeletal Muscle Organization

14. Skeletal Muscle Organization

15. Muscle fiber: an individual muscle cell. Sarcolemma: The plasma membrane. Sarcoplasm: the cytoplasm. Sarcoplasmic reticulum (SR): the specialized smooth endoplasmic reticulum, which stores, releases, and retrieves calcium ions. T-tubules: extensions of the sarcolemma into deep of the muscle fiber Terminal cisternae: the portion of the SR adjacent to T tubule. Triad: The arrangement of a T-tubule with the membranes of SR on either side. Two terminal cisternae and the T tubule between them. Skeletal Muscle Organization

16. Myofibril: long, cylindrical organelle that runs parallel within the muscle fiber and contains the sarcomeres. Sarcomere: the functional unit of a skeletal muscle fiber, a highly organized arrangement of the contractile myofilaments actin (thin filament) and myosin (thick filament). A myofibril is composed of many sarcomeres running along its length; thus, myofibrils and muscle cells contract as the sarcomeres contract. Skeletal Muscle Organization

17. Muscle Fiber Microanatomy

18. Muscle Fiber Microanatomy

19. The functional unit of a skeletal muscle fiber. A highly organized arrangement of the contractile myofilaments actin (thin filament) and myosin (thick filament). Z-discs (also called Z-lines): the anchoring point for actin myofilaments. Sarcomere is the area between two Z discs M line: the anchoring point for myosin myofilaments. Troponin and tropomyosin: regulatory proteins play important role in muscle contraction. Sarcomere

20. Sarcomere

21. Due to the way thin and thick filaments arranged, striations appear on the muscle fiber. When the two filaments overlap they create a darker area under microscope called the dark band (A band). When there is no overlap, the thin filament area appears lighter (brighter) under microscope which is called the light band (I band). The sequence of light and dark band is the striation. Sarcomere

22. Sarcomere Skeletal muscle fibers under microscope. Purple arrows point to nuclei of a single muscle fiber. Striation is seen. UMICH Webscope ( https://tinyurl.com/y7ydfekl )

23. Myofibrils A band I band I band Actin Myosin Z disc Sarcomere

24. Myofibrils (cont.) muscle relaxed muscle contracted sarcomere sarcomere

25. Muscle Contraction Whole muscle contraction is a result of the contraction at the sarcomere level. Skeletal muscle must receive a signal from nervous system in order to contract. As a result of the signal a sequence of events take place at different areas in the muscle fiber, collectively these events lead to muscle contraction. (https://www.youtube.com/watch?v=HulbYOoFieA).

26. Excitation-Contraction Coupling Muscle contraction is referred to as “excitation-contraction coupling”. For a skeletal muscle fiber to contract, its membrane must first be “excited” or stimulated to fire an action potential. The muscle fiber action potential, which sweeps along the sarcolemma as a wave, is “coupled” to the actual contraction through the release of calcium ions (Ca++) from the SR. Once released, the Ca++ forces the shielding proteins to move aside so that the actin-binding sites are available for attachment by myosin heads. The myosin then pulls the actin filaments toward the center, shortening the muscle fiber. Therefore, every excitation is coupled with contraction

27. Muscle Fiber Contraction Summary of the excitation steps : A signal coming from nervous system must arrive and stimulate the muscle. Another electrical signal known as action potential must be generated and propagated along sarcolemma Action potential must be transferred deep into muscle fiber and reach the sarcoplasmic reticulum through T tubules. Ca 2+ ions released from the SR. Sarcolemma returns to its resting (unstimulated) status and ready for the next signal.

28. The Neuromuscular Junction The site where a motor neuron’s terminal meets the muscle fiber. Every skeletal muscle fiber in every skeletal muscle is innervated by a motor neuron at the NMJ. Excitation signals from the neuron are the only way to functionally activate the fiber to contract. The Neuromuscular Junction By Ahmed Katsha

29. Motor neuron: a neuron that signals contraction of a skeletal muscle fiber. One motor neuron may contact several muscle fibers. Each neuron with its associated muscle fibers is called a motor unit. Neurons and Muscles Motor Unit

30. Events at Neuromuscular Junction A neuronal action potential arrives to the NMJ. The axon terminal releases a chemical messenger, or neurotransmitter, called acetylcholine ( ACh ). The ACh molecules diffuse across a space called the synaptic cleft and bind to ACh receptors located within the motor end-plate of the sarcolemma on the other side of the synapse.

31. Events at Neuromuscular Junction Once ACh binds, a channel in the ACh receptor opens and positively charged ions can pass through into the muscle fiber, causing it to depolarize, meaning that the membrane potential of the muscle fiber becomes less negative (closer to zero.)

32. Events at Neuromuscular Junction Once AP is propagated along the sarcolemma it arrives to T tubules and runs down through them.

33. Events at Neuromuscular Junction As AP progress along T tubules it opens the Ca +2 voltage gated channels located on the terminal cisternae.

34. Events at Neuromuscular Junction As the membrane depolarizes, another set of ion channels called voltage-gated sodium channels are triggered to open. Sodium ions enter the muscle fiber, and an action potential rapidly spreads (or “fires”) along the entire membrane to initiate excitation-contraction coupling. As Na+ enter the muscle, the inner side of sarcolemma becomes positive. This leads to local depolarization called end plate potential

35. Events at Neuromuscular Junction Ach Na + chemical gated channel Na + / K + Voltage gated channel K + By Ahmed Katsha Action Potential

36. End Plate Potential Due to concentration differences, Na + diffuses through the channels. This triggers AP that will spread along the sarcolemma opening all voltage gated Na + channels on its way.

37. End Plate Potential Action Potential Na + Na + Voltage gated channel K + Voltage gated channel K + By Ahmed Katsha

38. Events at Neuromuscular Junction Immediately following depolarization of the membrane, it repolarizes, re-establishing the negative membrane potential to start a new cycle of events. Repolarization involves opening of K + voltage gated channels to allow K + leave the muscle fiber and thus restore the membrane potential. Na + channels already closed since no more stimulation is coming (Ach is already removed from the synaptic cleft)

39. Events at Neuromuscular Junction K + By Ahmed Katsha

40. Action Potential Phases Depolarization: membrane loses its resting membrane potential due to Na+ gates opening. Repolarization: membrane restores its membrane potential due to closing Na+ gates and opening K+ gates.

41. Motor End Plate Action potential by Ahmed Katsha

42. Events at Neuromuscular Junction Meanwhile, the ACh in the synaptic cleft is degraded by the enzyme acetylcholinesterase ( AChE ) so that the ACh cannot rebind to a receptor and reopen its channel, which would cause unwanted extended muscle excitation and contraction. Ionic conditions of resting state are restored by Na+/K+ pump

43. The Coupling Ca +2 ions binds to troponin causing a shape change in it. As troponin changes its shape, it moves tropomyosin away from the actin’s binding sites. Myosin heads are able to bind to actin beads, a process called “cross-bridge”.

44. Muscle Fiber Contraction ATP molecule is used to break the cross-bridge and bend the myosin head away from the actin.

45. Muscle Fiber Contraction ATP quickly turned into ADP and inorganic phosphate (Pi), allowing the myosin head to bind the actin again.

46. Muscle Fiber Contraction Once ADP and Pi leave the myosin head, it pivots toward the center of the sarcomere, pulling the actin along with it. New ATP molecule breaks the cross-bridge and the process is repeated as long as Ca +2 binds troponin.

47. Contraction of Skeletal Muscle Fibers Two models: Excitation-contraction (E-C) coupling. Sliding Filament theory of contraction

48. The Sliding Filament Model of Contraction When signaled by a motor neuron, a skeletal muscle fiber contracts as the thin filaments are pulled and then slide past the thick filaments within the fiber’s sarcomeres. The sliding can only occur when myosin-binding sites on the actin filaments are exposed by a series of steps that begins with Ca++ entry into the sarcoplasm

49. The Sliding Filament Model of Contraction

50. Excitation/Contraction Coupling (summary) Action potential arrives to the muscle fiber and transmitted down through the T tubule Ca +2 ions then released from sarcoplasmic reticulum They bind to the thin filament causing it to be able to bind to the thick filament (cross-bridge) . Thick and thin filaments start to slide against each other causing the fiber to contract. Collective contraction of all fibers cause the muscle to contract. You should be able to describe how a muscle contracts in these simple lines at least.

51. Relaxation of Skeletal Muscle Relaxing skeletal muscle fibers, and ultimately, the skeletal muscle, begins with the motor neuron, which stops releasing its chemical signal, ACh , into the synapse at the NMJ. The muscle fiber will repolarize, which closes the gates in the SR where Ca++ was being released. ATP-driven pumps will move Ca++ back into the SR. This results in the “ reshielding ” of the actin-binding sites on the thin filaments. Without the ability to form cross-bridges between the thin and thick filaments, the muscle fiber loses its tension and relaxes.

52. The Frequency of Motor Neuron Stimulation Muscle twitch: A single action potential from a motor neuron will produce a single contraction in the muscle fibers of its motor unit. A twitch can last for a few milliseconds or 100 milliseconds, depending on the muscle type. The tension produced by a single twitch can be measured by a myogram , an instrument that measures the amount of tension produced over time

53. The Muscle Twitch (cont.)

54. The Muscle Twitch (cont.) Three phases of muscle twitch Latent period : the action potential is being propagated along the sarcolemma and Ca++ ions are released from the SR. Excitation and contraction are being coupled but contraction has yet to occur. Period of contraction : The Ca++ ions have bound to troponin, tropomyosin has shifted, cross-bridges formed, and sarcomeres are actively shortening to the point of peak tension. Period of relaxation : tension decreases as contraction stops. Ca++ ions are pumped into the SR, and cross-bridge cycling stops, returning the muscle fibers to their resting state.

55. Energy for Contraction and ATP ATP supplies the energy needed for the muscle fiber to: To detach cross bridges Energy for the active-transport Ca++ pumps in the SR Na + /K + pump to restore membrane potential. The amount of ATP stored in muscle is very low, only sufficient to power a few seconds worth of contractions.

56. Providing Energy for Contraction Direct phosphorylation of ADP by creatine phosphate (CP) Creatine phosphate is a molecule that can store energy in its phosphate bonds . Acts as an energy reserve that can be used to quickly create more ATP Creatine phosphate can only provide approximately 15 seconds worth of energy, at which point another energy source has to be used

57. Providing Energy for Contraction There are three mechanisms by which ATP can be regenerated: Direct phosphorylation of ADP by creatine phosphate (CP) Anaerobic pathway: glycolysis and lactic acid formation Aerobic respiration

58. Providing Energy for Contraction

59. Providing Energy for Contraction (cont.) Aerobic respiration is the breakdown of glucose in the presence of oxygen (O2) to produce carbon dioxide, water, and ATP. Approximately 95 percent of the ATP required for resting or moderately active muscles is provided by aerobic respiration, which takes place in mitochondria.

60. Providing Energy for Contraction Aerobic respiration

61. Providing Energy for Contraction (cont.) Anerobic respiration Each glucose molecule produces two ATP and two molecules of pyruvic acid, which can be used in aerobic respiration or converted to lactic acid. If oxygen is not available, pyruvic acid is converted to lactic acid, which may contribute to muscle fatigue. This occurs during strenuous exercise when high amounts of energy are needed but oxygen cannot be sufficiently delivered to muscle.

62. Providing Energy for Contraction Anaerobic pathway: glycolysis and lactic acid formation

63. Interactions of Skeletal Muscles in the Body To produce a movement a skeletal muscle must also be attached to a fixed part of the skeleton. Insertion is the moveable end of the muscle that attaches to the bone being pulled. Origin is the end of the muscle attached to a fixed (stabilized) bone.

64. Interactions of Skeletal Muscles in the Body Although several muscles may be involved in an action, the principal muscle involved is called the prime mover , or agonist . A muscle with the opposite action of the prime mover is called an antagonist . Muscles only pull bones, never push. The opposite movement is produced by the anatgonist muscle.

65. Interactions of Skeletal Muscles in the Body By Anonymous - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14932207

66. Interactions of Skeletal Muscles in the Body

67. Questions to consider  How neurotransmitters change the ion permeability on the cell membrane?   The specific roles of Na+, K+ and Ca++ ions in each stem of muscle contraction. With what they interact and what do they lead to?  The sliding filament model: what slides over what?  Which component of the skeletal muscles is associated with Excitability, Elasticity, Extensibility and Contractility?

68. Questions to consider  What are the consequences of using a drug that intervene with the latent period? Think of what is the latent period and what happens there.  The components and subcomponents of the organelles in skeletal muscles. What effects a blocker for ACh receptor can induce over the long run of a person’s life? Think of how losing Ach receptors can affect the muscles.   

69. Questions to consider  The order of steps leading to muscle contractions. Make sure you understand the steps and the substeps .  How muscles induce movements? Test 1