STUDY GUIDE 10 PDF - Muscular Tissue

STUDY GUIDE: MUSCULAR TISSUE 1. Both cardiac and skeletal muscle tissues are striated, and smooth muscle is not. 2. Skeletal muscle cells have more than one nucleus, are large and run parallel to each other. 3. Cardiac muscle cells usually have only one, sometimes two, centrally located nuclei...

STUDY GUIDE: MUSCULAR TISSUE 1. Both cardiac and skeletal muscle tissues are striated, and smooth muscle is not. 2. Skeletal muscle cells have more than one nucleus, are large and run parallel to each other. 3. Cardiac muscle cells usually have only one, sometimes two, centrally located nuclei and are branched. 4. Cardiac muscle cells also are connected to each other via gap junctions. 5. Smooth muscle cells are small but form thick layers of hollow organs. 6. Like cardiac muscle cells, some smooth muscle cells communicate via gap junctions. 7. Skeletal muscle is voluntarily controlled. 8. Both cardiac and smooth muscle tissue are involuntary and auto rhythmic. 9. Major functions of skeletal muscle include: a. Producing body movement and storing nutrients as glycogen, proteins b. Maintaining posture (upright position) c. Generating heat d. Controlling entrance and exit 10. Four properties of muscle tissues are a. Electrical excitability b. Contractility c. Extensibility [property of muscle gives it the ability to stretch without damage] d. Elasticity [property of muscle gives it the ability to recoil] 11. Muscle fibers have many nuclei in order to produce large amounts of the enzymes and structural proteins needed for contraction. 12. Epimysium is the dense irregular connective tissue that surrounds the entire muscle. 13. Perimysium is a fibrous connective tissue that covers each fascicle of muscle and contains nerves and blood vessels that service the muscle fibers 14. Endomysium is the delicate connective tissue that surrounds the individual muscle fiber and contains a large capillary network. 15. The epimysium, perimysium, and endomysium are all continuous with the connective tissue to form a rope like tendon that attaches a muscle to the periosteum of the bone. 16. Aponeurosis is a wide and flat tendon. 17. Fascia lines the body wall and limbs that surround and support muscles. 18. Myoblast is embryonic cell (stem cell) that forms muscle fiber. 1 19. After the fusion of myoblasts, the muscle fiber loses its ability to go through mitosis. FIGURE 1 A: Tendon B: Perimysium C: Epimysium D: Muscle fiber or muscle cell E: Fascicle F: Muscle fiber or muscle cell G: Myofibrils H: Sarcolemma I: Filaments 20. Sarcolemma is plasma membrane of a muscle fiber (muscle cell) 21. Sarcoplasm is the cytoplasm of a muscle fiber. 22. Sarcoplasm stores glycogen and myoglobin, a red-colored protein that binds O 2. 23. Sarcoplasmic reticulum (SR) is the series of membraneous channels that surround each myofibril. 24. SR stores calcium ions (Ca2+) 25. Transverse tubules or T tubules are tunnels in from the surface toward the center of each muscle fiber. 26. Terminal cisterns are dilated end sac of the SR. 27. A T-tubule and two terminal cisterns on either side form a triad. 28. Myofibrils are contractile organelles of muscle cell. 29. The overlapping of thick and thin filaments and the prominent striations of the myofibrils make the entire skeletal muscle fiber appear striated. 30. Microfilaments are smaller proteins within myofibrils. 31. There are two types of microfilaments: thin and thick filaments. 2 32. Thin and thick filaments do not extend the entire length of muscle fiber. Instead, they are arranged in compartment called sarcomere. FIGURE 2 A: Z disc B: Thin actin filament C: Thick myosin filament D: M line E: Titin F: Sarcomere G: “I” band H: Zone of overlap I: H zone J: “A” band 33. Sarcomere is the basic functional unit of a myofibril of a skeletal muscle fiber. 34. Z line or Z disk is narrow, plate-shaped region of dense protein material that separates one sarcomere to another. 35. In sarcomere, thick and thin filaments are linked laterally by filaments of the M line. 36. A band: the darker middle area of sarcomere that contains thick & thin filament. 37. I band: the light area of the sarcomere that contains thin filament only. 38. H zone: the narrow area in the center of the A band that contains thick filament only. 39. The zone of overlap is a dark region where thin and thick filaments lie side by side. 40. Thin filaments at either end of sarcomere are attached to the Z line (Z disc). 41. Myosin is the main component of the thick filament and functions as a motor protein of muscle tissue. 42. Actin is the main protein of the thin filament. 43. Each thin filament consists of a pair of protein actin strands wound together into a helix. 44. Actin and myosin are contractile proteins of the muscle fiber. 45. Tropomyosin and troponin are regulatory proteins of the muscle fibers. 46. Titin, myomesin, nebulin, α-Actinin, and dystrophin are structural proteins of the muscle fibers. 47. Titin is the largest size protein in the muscle fiber that extends from the Z disk to M line. 3 48. The protein of M line is Myomesin. 49. The part of the titin that extends from the Z disc is very elastic. Thus, titin accounts for much of the elasticity and extensibility of myofibrils. 50. Dystrophin is protein used to reinforce the sarcolemma and help transmit the tension generated by the sarcomeres to the tendons. 51. Nebulin is a long, non-elastic protein wrapped around the entire length of each thin filament. 52. At rest, active sites of actin (myosin-binding site) thin filament are blocked (covered) by tropomyosin molecules. 53. At rest, the tropomyosin molecule is held in place by troponin. 54. A Troponin molecule consists of three globular subunits: a. Unit 1 binds to tropomyosin b. Unit 2 binds to G-actin c. Unit 3 binds to calcium ions. 55. When a skeletal muscle fiber contracts in the sliding filament mechanism, a. Z line (Z disk) moves closer together b. The H zones and I bands get smaller c. The width of the A band remains constant d. The zone of overlap gets larger (more zone of overlaps between thin & thick filament) 56. Contraction of myofibrils within a muscle fiber begins when calciumion is released from the terminal cistern of sarcoplasmic reticulum. 57. When cross-bridges bind to the active site of actin thin filaments (myosin binding site), the thick filaments pivot toward the M line. 58. Active sites on the actin thin filament become available (exposed) for binding when calcium ion binds to troponin subunit. Once calcium ion binds to troponin, troponin then moves tropomyosin away from the myosin-binding sites of thin filament. 59. The contraction cycle includes a. Step 1: Myosin head hydrolyses ATP and become energized and oriented b. Step 2: Myosin head binds to actin , forming the cross bridge c. Step 3: Myosin head pivots, pulling the thin filament past the thick filament toward center of the sarcomere (power stroke) d. Step 4 : Another ATP binds attches to the cross bridge, myosin head detaches from actin. Then the cycle repeats 4 60. Cross bridges a. are portions of thick filament (myosin head) b. act as (an enzymes) ATPase during the contraction cycle of muscle c. generate force 61. ATP hydrolysis reaction energizes the myosin head. 62. In summary, to form cross-bridges, a. ATP must be broken down by enzyme ATPase b. Calcium ions must be present in the sarcoplasm c. Myosin binding sites (actin active site) must be exposed 63. When a muscle fiber is relaxed, the concentration of Ca2+in the sarcoplasm is very slow, but the concentration of Ca2+ in the sarcoplasm reticulum (SR) is very high. As a result, to trigger muscle contraction, Ca2+ must be released from SR. FIGURE 3 A: Myofibril B: Mitochondrion C: Triad D: Transcerse tubule E: Terminal cistern F: SR G: Nucleus H: Thick filaments I: Thin filament J: Sarcomere K: Sarcoplasm L: Sarcolemma 64. An action potential or a (depolarization) or a (nerve impulse) is required for the SR releases Ca2+ into sarcoplasm because when an action potential travels along the T. Tubule to open the voltage gated Ca 2+ channel allows a large amount of calcium flow out of the SR. 65. The sequence of events that links excitation (generation an action potential) to the contraction is called excitation-contraction coupling. 5 66. To generate an action potential, acetylcholine (Ach), a neurotransmitter must be released at the neuromuscular junction (NMJ) 67. NMJ is the synapse between the terminal end of a somatic motor (axon terminal) neuron and a portion sarcolemma (called Motor-End-Plate) of a skeletal muscle fiber. FIGURE 4 A: axon terminal B: synaptic end bulb C: Axon collateral D: Somatic motor neuron E: Skeletal muscle fiber 68. Receptors for acetylcholine are located on the motor-end plate (the region of the sarcolemma opposite the synaptic end) 69. There are approximately 40 million receptors for Ach that are found in the motor-end-plate. 70. Somatic motor neurons (voluntary control) provide nerve impulses that stimulate skeletal muscle to contract. 71. Each skeletal muscle fiber is controlled by a neuron at a single neuromuscular junction. 72. Synaptic cleft is the narrow space between the neuron and the muscle fiber. 73. Action potentials are conducted into a skeletal muscle fiber by transverse tubules (T-tubules). 74. The cytoplasm of the synaptic terminal at NMJ contains mitochondria and vesicles filled with neurotransmitter acetylcholine 75. When acetylcholine binds to receptors at the motor-end plate, the muscle membrane becomes more permeable to sodium ions (Voltage-gated Na+ channel opens to allow Na+ ions entering inside the sarcolemma) 76. The SR (sarcoplasmic reticulum) releases calcium in response to an arrival of action potential. 6 77. The order of steps in generation an action potential a. Step 1: The arrival of a nerve impulse at a motor neuron opens voltage-gated calcium Ca2+ channel in the sarcolemma, allowing Ca2+ enter to the synaptic terminal to trigger the releasing of acetylcholine. b. Step 2: Ach diffuses across the synaptic cleft by exocytosis and binds to receptors in the motor-end- plate. The binding opens voltage-gated sodium Na+ channel in the sarcolemma, allowing Na+ enters to the sarcoplasm. c. Step 3: The influx of Na+ produces a depolarization of the sarcolemma called “muscle action potential” d. Step 4: The muscle action potential that propagates along the T. Tubules triggers the opening of voltage-gated Ca channel in the sarcoplasmic reticulum (SR). SR releases Ca into sarcoplasm e. Step 5: Termination of Ach by enzyme Acetylcholinesterase (AChE) f. Step 6: Ca2+ binds to troponin on the thin filament, exposing the active site or myosin-binding site of actin. g. Step 7: Crossbridges are formed and contraction cycle begins. h. Step 8: When the generation of action potential ends, Ca2+ is pumped back to the SR by an active transport. 78. A muscle fiber develops its greatest tension when there is an optimal zone of overlap (sarcomere length is 2.0- 2.4 μm) between thick and thin filament. This dependency is the length-tension relationship. 79. Muscle has three ways to produce ATP: a. Producing ATP from creatine phosphate by direct phosphorylation b. Producing ATP from anaerobic glycolysis c. Producing aerobic respiration 80. Creatine phosphate acts as an energy reserves in muscle tissue. 7 81. In skeletal muscles, the combined amounts of creatine phosphate and ATP provide enough energy for the muscle to contract maximally for approximately 15 seconds. 82. Anaerobic glycolysis supplies enough ATP for muscles for two minutes of maximal activity. 83. Aerobic respiration supplies enough ATP for muscles during periods of rest or moderate exercises (running, jogging, swimming, and walking) 84. At peak levels of exertion, mitochondria can provide only one-third (33%) of the ATP needed. The remainder comes from glycolysis. 85. The factors that lead to muscle fatigue include a. Inadequate release of calcium ions from the SR b. Depletion of creatine phosphate c. Insufficient oxygen d. Depletion of glycogen and other nutrients e. Buildup lactic acid f. Failure of action potentials in the motor neurons to release enough Ach 86. When energy reserves in a muscle are exhausted and lactic acid levels increase, muscle fatigue occurs. 87. Motor unit is a term describes a somatic motor neuron and all the skeletal muscle fibers it stimulates. 88. The ratio of motor neurons to muscle fiber is the greatest in muscles that control the eye and the tongue. 89. Twitch is a brief contraction of all muscle fibers in a motor unit in response to a single action potential moving down the somatic motor neuron. 90. A myogram is a record of muscle contraction. 91. A myogram of twitch contraction includes the latent period, the contraction period, and the relaxation period. 92. The refractory period is a period that the muscle fiber loses its excitability and cannot response to a second stimulus. 93. During the refractory period, additional oxygen is required to metabolize the lactic acid produced during exercise. 94. Treppe is the increased strength of a contraction that occurs when a second stimulus arrives after the muscle fiber has relaxed completely following the previous stimulus. 95. Wave summation is the increased strength of a contraction that occurs when a second stimulus arrives before the muscle fiber has relaxed completely. 8 96. Complete tetanus (fused tetanus): a muscle that is stimulated so frequently that the relaxation phase is completely eliminated 97. Incomplete tetanus (unfused tetanus): a muscle producing peak tension with rapid cycles of contraction and relaxation. 98. Tetanus is due to a toxin that makes the muscle cell membrane more permeable to calcium ions (Ca2+), causing powerful tetanic contraction. FIGURE 5 a) Treppe b) Wave summation c) Incomplete tetanus (unfused tetanus) d) Complete tetanus (fused tetanus) 99. Recruitment is the increase in muscle tension that is produced by increasing the number of active motor units. 100.Muscle tone is a small amount of tension in the muscle at rest due to weak, involuntary contractions of its motor units. 101.Hypotonia refers to decreased or lost muscle tone. 102.Flaccid is a state of limpness in which muscle tone is lost. 103.Hypertonia refers to increased muscle tone. 104.Spasticity is an increased muscle tone associated with an increase in tendon reflexes. 105.Rigidity is an increased muscle tone in which tendon reflexes are not affected (tetanus). 106.Isometric contraction is the type of contraction in which the muscle fibers produce tension but do not shorten nor lengthen. (Object cannot be moved) 9 107.Isotonic contraction is the type of contraction in which the muscle fibers produce tension while muscle length is changed. 108.Concentric isotonic contraction, the muscle fiber shortens. (object is lifted) 109.Eccentric isotonic contraction, the muscle fiber lengthens. (object is dropped) 110.Cori cycle is a cycle in the liver in which the lactic acid is converted to pyruvic acid and glucose. 111.Fast fibers: Fast glycolytic fibers (FG) a. Large diameter b. Produces powerful contraction c. Less resistant to fatigue d. Glycolytic fiber: fast fibers have fewer mitochondria and large of glycogen reserves and that why it uses anaerobic respiration e. low concentration of myoglobin (White meat) 112.Slow fibers: Slow oxidative fiber (SO) a. Small diameter b. MOST resistant to fatigue c. Oxidative fibers have many mitochondria. That is a reason why they use aerobic respiration. d. high concentration of myoglobin (Red meat) e. Produce slow contraction 113.Activities during aerobic endurance: a. Most of the muscle’s energy is produced in mitochondria b. Krebs cycle is a main source of ATP (36 ATPs) c. No oxygen debt d. Oxygen is required e. Dependent on slow oxidative fibers f. Fatigue resistant (sustained contraction for hours) 114.Activities during anaerobic endurance: a. Most of the muscle’s energy is produced in cytoplasm by glycolysis b. Glycolysis is a main source of ATP (2ATPs) c. Oxygen debts are common d. Dependent on fast glycolytic fibers e. Oxygen is NOT required f. Muscle fatigue quickly (not able to have sustained contraction for hours) 10 115.Rigor mortis is a condition in which muscles are in a state of rigidity 3-4 hour after death and last about 24 hours. 116.The mechanisms of rigor mortis is due to calcium ions leak out of the SR (allowing myosin heads to bind to actin) and muscle fibers run out of ATP (causing the cross-bridges cannot detach from actin). 117.Rigor mortis disappears as proteolytic enzymes from lysosomes digest the cross-bridges) 118.After prolonged strenuous exercise has stopped, heavy breathing will often continue for several minutes in order to provide the oxygen needed to a. convert the lactic acid produced during exercise back into glycogen b. resynthesize creatine phosphate c. replace oxygen displaced from muscle myoglobin 119.There are two types of smooth muscle single-unit visceral smooth muscle and multi-unit smooth muscle. 120.In single-unit smooth muscle tissue, action potentials are initiated in response to neurotransmitters, hormones, or an auto-rhythmic signal. The action potential spreads throughout the tissue by moving through gap junctions that connect all the muscle cells together within the tissue. 121.Single-unit smooth muscle is found in the skin and in tubular arrangements that form part of the walls of small arteries and veins and of hollow organs such as the stomach, intestines, uterus, and urinary bladder. 122.In multi-unit smooth muscle tissue, muscle cells have few gap junctions with neighboring cells and thus must be excited by their own motor neuron terminal. 123.Multi-unit smooth muscle is found in the walls of large arteries, in airways to the lungs, in the arrector pili muscles that attach to hair follicles, in the muscles of the iris that adjust pupil diameter, and in the ciliary body that adjusts focus of the lens in the eye. 124.Major characteristics of smooth muscle cells: a. Smooth muscle cells are uninucleate b. Smooth muscles lack sarcomeres c. Thin filaments are attached to dense bodies d. Transmitting the contractile forces from cell to cells throughout the muscle tissue. e. Involuntary control (pacesetter cells) 125.Major functions of smooth muscle: a. Altering the diameter of the respiratory passageways b. Moving food materials along the digestive tract c. Moving sperms in the male reproductive tract and oocytes in the uterine tract 11  d. Expelling fetus by contraction of the wall of the uterus e. Acting as a sphincter 126.Smooth muscle contracts when calcium ions Ca2+ interact with calmodulin which activate the enzyme myosin light chain kinase, enabling myosin heads to attach to actin. 127.Plasticity is an ability of the smooth muscle to function over a wide range of lengths. 128.Muscle tissue is capable of undergoing the stress-relaxation response when stretched is single-unit smooth muscle fibers. 129.Individual who lifts weights build larger muscles because skeletal muscles increase number of myofibrils but not number of cells. 130.Mitochondrial activity in skeletal muscle cells are usually efficient, but can have limited ATP production if there is limited O2 availability 131.Myasthenia Gravis is an autoimmune disorder that targets the ACh receptors at the NMJ and ultimately reduces the number of available receptors. Treat the patient with a drug that inhibits the activity of acetylcholinesterase will increase contraction. 132.Cramp occurs because the relaxation phase of a muscle contraction is often prolonged in a fatigued muscle, raising the likelihood of fused summation of action potentials causing painful disturbances to a skeletal muscle. 12