Medic 14 AP Chapter 7

  1. Chapter objectives
    • Describe the functions of skeletal muscle tissue
    • Describe the organisation of muscle at the tissue level
    • identify the structural components of a sarcomere
    • explain the key steps involved in the contraction of a skeletal muscle fiber
    • compare the different types of muscle contractions
    • describe the mechanism by which muscles obtain and use enerty to power contractions
    • relate the type of muscle fibers to muscular performance.distinguish between aerobic and  anerobic endurance and explain their implication for muscular performance.
    • contrast skeletal, cardiac, and smooth muscles in term of structure and function
    • Identify the main axial muscles of the body, along with their action.Identify the appendicular muscles of the body,along with their actions
    • describe the effects of aging on muscle tissue
    • discuss the functional relatonship between the muscular system and other organ systems
  2. aer
    air; aerobic
  3. an
  4. bi
  5. caput
    head; caput humeri
  6. clavis
    claviclel; clavicle
  7. di
    two; digastricus
  8. epi-
    on: epimysium
  9. ergon
    work; synergist
  10. fasciculus
    a bundle: fascicle
  11. gaster
    stomach; gastronemius
  12. hyper
    above; hypertrophy
  13. iso-
    equal; isometric
  14. kneme
  15. lemma
  16. meros
    part; sarcomere
  17. metron
    measure; isometric
  18. mys
    muscle; epimysium
  19. peri-
    around; perimysium
  20. playts
    flat; platysma
  21. sarkos
    flesh; sarcolemma
  22. syn-
    together; synergist
  23. tetanus
    convulsive tensions; tetanus
  24. tonos
    tension; isotonic
  25. trope
    a turning; tropomyosin
  26. -trophy
    nourishing; atrophy
  27. Muscle tissue
    consists of elongated muscle cells that are highly specialized for contraction
  28. Three types of muscle tissue
    • Skeletal
    • Cardiac
    • smooth
  29. Skeletal muscles
    • are organs composed primarily of skeletal muscle tissue,
    • but also contains connective tissues, nerves, and blood vessels
    • These muscles are directly or indirectly attached to bones of the skeleton
    • 700 skeletal muscles
  30. Functions of skeletal muscles
    • Produce movement of the skeleton
    • Maintain posture and body position
    • Support soft tissues
    • Gaurd entrances and exits
    • Maintain body temperature
  31. Three layers of connective tissue
    • Epimysium
    • Permysium
    • Endomysium
  32. Epimysium
    • Surrounds the entire muscle
    • layer of collagen fibers that separates the muscle from surrounding tissues and organs
  33. Perimysium
    • Connective tissue fibers divide the skeletal muscle into bundles of fingers called fascicles
    • in addition to collagen and elastic fibers, it contains blood vessels and nerves that supply the fasicles
  34. Endomysium
    • withing a fasicle, surrounds each skeltal muscle fiber and ties adjacent muscle fibers together.
    • Stem cells scattered help repair damaged muscle tissue
  35. At the end of each muscle
    collagen fibers of all layers come together to form either a tendon or a aponeirosis
  36. Aponeuroses
    connect different skeletal muscles together
  37. Skeletal muscles only contract
    • under stimulation from the CNS.
    • Axons (nerve fibers) penetrate the epimysium, branch through the perimysium and enter the endomysium to control indivdual muscle fibers
  38. Skeletal muscles are often called
    Voluntary muscles
  39. Sarcolemma
    • "cell membrane" of a muscle fiber surrounds the sacroplasm (cytoplasm)
    • openings across the surface of the sarcolemma lead into a networkd of nattow tubules called
    • transverse tubules or T tubules
    • T tubule plats a major tole in coordination the contration of muscle fibers
  40. Muscle contraction occurs through the orderly interaction of
    both:electrical and chemical events
  41. Myofibrils
    • Are encircled by t tubules myofibrils
    • Are bundles of thick and thin myofiliments, that are protein filaments that contain actin and myosin
    • Actin are found in thin filaments
    • mysosin are in thick filaments
    • are resonsible for muscle contraction
    • mitochondria and grandules of glycogen are scattered among them
  42. Sarcoplasmic reticulum
    • whcih is a specialized for of smooth endoplasmic reticulum.
    • Whenever a T tubule enricles a myofibil, the tubule is tightly bought fo the membranes of the SR
  43. On either sides of a t tubule  expanded chambers of the SR called
    Terminal Cisternae

    T Tubules are sandwiched between Terminal Cisternae

    they contain high concentraions of calcium ions
  44. Sacromeres
    • Repeating functional units of myofilaments
    • smallest functional unit of muscle fiber
    • interactions between the thick and thin filaments are responsible for muscle contraction
  45. Z lines
    are bounddaries of each sarcomere
  46. Thin filaments extend toward the center of the sarcomere and pass among the thick filaments in the
    zone of overlap
  47. M line
    is made up of proteins that connect the central protions of each thick filament to its neighbors.
  48. A band
    contains thick filaments
  49. I band
    the light region between two sucessive A bands , inculding the Z line
  50. Each actin molecule has
    an active site capable of interacting with myosin.
  51. Tropomyosin
    protein that covers the active sites along the thin filament
  52. Tropomyosin strands are held in postion by
    molecules of tropoin
  53. Calcium
    • is the key that unlocks that actives sites and starts a contraciton.
    • calcium binds to troponis, the protein changes shape.
  54. Sliding Filament theory for Sarcomere contraction
    I bands get smaller, the Z lines move closer together, and zone of overlap gets larger but the width of the A bands do not change
  55. Neuromuscular Junction
    Is the communication link between the nervous system and a skeletal muscle fiber.
  56. Motor Neuron
    Nerve cell that controls each skeletal muscle fiber
  57. A single axon of the neuron branches withing the perimysium to from branches, the ends of these branches are called
    Synaptic terminal
  58. Cytoplasm of the synaptic terminal comtains
    mitochondria and vesicles filled with ACh acetychoine
  59. Acetylcholine
    • is a neurotransmeitter whcih is a chemical released by a neuron to communicate with other cellls. 
    • Neurotransmitters change the properties of other cells membranes, in this case permiablilty.
    • the change in the sarcikemma triggers contraction of the muscle fibers
  60. Synaptic cleft
    Seperates the synaptic terminal from the sarcolemma
  61. Motor end plate
    is the portion of the membrane that contain receptors that bind ACh
  62. Both the synaptic cleft and motor end plate contain the enzyme called
    • Acetylcholinesterase (AChE)
    • Which breaks down molecules of ACh
  63. AChE (acetylcholinesterase)
    • Also know as cholinesterase
    • Is contained in both the synaptic cleft and the motor end plate.
    • This enzyme breaks down molecules of ACh
  64. Action potential
    Electrical impulse in the sarcolemma
  65. Neurons control skeletal muscle fibers by...
    Stimulating the production of an action potential
  66. Function in the neuromuscular junction
    Arrival of an action potential of the synaptic terminal.
  67. Function in the neuromuscular junction
    • Release of ACh when action potential from the axon reaches the synaptic terminal.
    • Vesicles in the synaptic terminal fuse with the neuronal membrane and dump their contents into the synaptic cleft.
  68. Function in the neuromuscular junction
    • ACh binding at the motor end plate
    • The  diffusion across the synaptic cleft and binding of ACh to the receptors on the sarcolemma, increases the membrane permeability to sodium ions.
    • Sodium ions then rush into the cell, this produces an action potential in the sarcolemma.
  69. Function in the neuromuscular junction
    • Appearance of an action potential in the sarcolemma.
    • An action potential spreads across the surface of the sarcolemma and down all of the transverse tubes toward the terminal cisterne.
    • triggers a sudden,massive release of calcium ions by the terminal cisternae.
    • While the contraction process occurs AChE breaksdown ACh.
  70. Myasthenia gravis
    • Is an autoimmune disease charterized by muscle weakness and fatique
    • Anti bodies attack  acetycholine receptors and impair function of the ACh receptor at the neuromuscular junction.
    • Treated by long acting cholinesterase agents.
  71. In a resting sarcomere...
    • Each cross-bridge is bound to a molecule of ADP and phosphate group (PO43-),
    • which are products of the breakdown of an ATP molecule.
  72. The cross-bridge of the resting sarcomere stores...
    • the energy released by the breakage of the high energy bond.
    • Thus, the resting cross bridge is "primed for contraction"
  73. The contraction process steps
    • Active-site exposure.
    • The active site is exposed following the binding the calcium ions  (Ca2+) to troponin.
  74. The contraction process steps
    Cross bridge formation
    The myosin cross-bridge forms and attaches to the exposed active site on the thin filaments.
  75. The contraction process steps
    • Pivoting of myosin head.
    • the attached myosin head pivots toward the center of the sarcomere, and the ADP and a phosphate group are released.
    • This steps uses the energy that was stored in the myosin molecule at rest.
  76. The contraction process steps
    • Cross- bridge detachement
    • The cross-bridges detach when the myosin head binds another ATP molecule.
  77. The contraction process steps
    • Myosin reactivation 
    • The detached myosin head is reactivated as it splits the ATP and captures the released energy. The entire cycle can now be repeated, beginning with step 2.
  78. Depolarization
    In biology, depolarization is a change in a cell's membrane potential, making it more positive, or less negative. In neurons and some other cells, a large enough depolarization may result in an action potential.
  79. Two ways to block the neuromuscular junction
    • Depolarizing agents- that substitute for ACh
    • Non-depolarizing agents- that block the reuptake of ACh into the nerve terminal
  80. Depolarizing neuromuscular blockers
    • They substitute ACh
    • Unlike Ach, they act over a prolonged time
    • That results in continued muscle depolarizaion and muscle paralysis
    • Due to Stimulating affect they produce fasiculations
  81. Non depolarizing neuromuscular blockers
    • They block the reuptake of ACh in the nerve terminal
    • This produces excess ACh, and inhibits the stimulation of the muscle.
    • They do depolarize the affected fibers and do not cause fasiculations.
  82. Botulism
    From the consumption of foods (often canned or smoked) contaminated with the bacteria Clostridium perfringens. that prevents the release of ACh, that leads to potentially fatal muscular paralysis
  83. Summary of steps involved in Skeletal muscle contraction
    At the neuromuscular junction, ACh released by the synaptic terminal binds receptors to the sarcolemma.
  84. Summary of steps involved in Skeletal muscle contraction
    The resulting change in the membrane potential of the muscle fibers leads to the production of an action potential that spreads across the entire surface of the muscle fibers and T tubes.
  85. Summary of steps involved in Skeletal muscle contraction
    The SR releases  stored calcium ions which increases the calcium concentration of the sarcoplasm in and around the sarcomeres.
  86. Summary of steps involved in Skeletal muscle contraction
    Calcium ions bind to the triponin, which results in the movement of the active sitres on the thin filaments (actin). Cross bridges form when myosin heads bind to active sites.
  87. Summary of steps involved in Skeletal muscle contraction
    The contraction begins as repeated cycles of cross bridge binding,pivoting, and detachment occur, powered by ATP, these events produce filament sliding and the muscle fiber shortens
  88. Summary of steps involved in Skeletal muscle contraction
    Active potential generation ceases as ACh is broken down by AChE
  89. Summary of steps involved in Skeletal muscle contraction
    The SR reabsorbs calcium ions, and the concentration of calcium ions in the sarcoplasm declines.
  90. Summary of steps involved in Skeletal muscle contraction
    when  calcium ion concentration approach normal resting levels, the triponin and trpomyosin molecules return to their normal positions. this change recovers the active sites and prevents further cross bridge interaction.
  91. Summary of steps involved in Skeletal muscle contraction
    Without cross-bridge interactions, further sliding cannot take place and the contraction will end.
  92. Summary of steps involved in Skeletal muscle contraction
    Muscle relaxation occurs, and the muscle returns passively to its resting length
  93. When muscle contracts, they pull on collagen fibers, producing an active force called
  94. Tension applied  to an object tends to
    Pull the object toward the source of tension
  95. The passive force that opposes movement
  96. before movement can occur the applied tension must overcome the objects
  97. Compression
    A push applied to an object- tends fto force the object away from the souce of compression
  98. Ammount of tension of a skeletal muscle depends on
    • the frequecy of neural stimulation
    • the number of muscle fibers activated
  99. Twitch
    is a single stiulus contraction -relaxation squence in a muscle fiber
  100. Summation
    If a second stimilus arrivces before the relaxation phase has ended, a second , more powerful contraction occurs.
  101. Incomplete tetanus
    A muscle that produces almost peak tension during rapid cycles of contraction and relaxation.
  102. Complete tetanus
    occurs when the rate of stimulation is increed until the relaxation phase is completely eliminated which produces maximum tension.
  103. Tetanus
    • caused by clostridum tetani
    • deep tissue injuries
    • when active in the body the toxin supresses the machanism that regulates motor neuron activity
  104. A typical skeletal muscle
    contains thousands of muscle fibers
  105. Motor Unit
    All the muscle fibers by a single motor neuron consitiute a motor unit
  106. Recruitment
    • is the activation of more and more motor units 
    • result is a smoth,steady, increase in muscle tension.
  107. All voluntary movements invole the sustaind contracions of skeletal muscle fibers in imcomplete tetanus. The force exerted can be increaed by increading the requency of the action potentials or the number of stimulated motor units (recruitment)
  108. Classifictions of muscle contractions
    • Isotonic contraction
    • Isometric contraction
  109. Isotonic contraction
    Tehsion rises and the skeltal muscles length changes. thension in the muscle remains a constant level until relaxation occurs.
  110. Isometric contraction
    the muscle as a whole does not chage length, and the tension produced never exceeds the resistance
  111. Elongation of a muscle
  112. An active skeletal muscle fiber may require: how much ATP
    600 trillion  molecules of ATP a second
  113. A resting muscle fiber only contains  energy reserves to sustain a contraction untill
    • Additional ATP can be generated.
    • Muscle fibers will generate ATP at roughly the same rate as it is used.
  114. Primary funciton of ATP
    • transfer energy from one location to another
    • NOT the long term storage of energy
  115. At rest, a skeletal muscle fiber produces  more ATP then it needs. Under these conditions ATP transfers the energy to
  116. Creatine Phosphate (CP)
    ATP+ creatine ---> ADP + Creatine Phosphate
  117. During each contraction, each cross bridge breaks down ATP and produces ADP and a phosphate group
    Creatine Phosphate  recharges ADP to ATP

     ATP+ Creatine Phosphate---> ADP +Creatine
  118. Creatine phosphokinase (CPK or CK)
    Regulates the rechage of ADP to ATP with Creatine Phosphate
  119. ATP is generated by
    • Aerobic metabolism in the mitochodria
    • and through Glycolysis in the cytoplasm
  120. Aerobic metabolism accounts for 95% of ATP needed by a resting cell. In this process,
    Mitochondria absorb oxygen, ADP, Phosphate ions and small organic substrate molecules in the cytoplasm.
  121. The organic substrates are carbon chains produced by the breakdown of carbohydrates, lipids or proteins
    • These substrates enter the TCA (tricaboxylic acid) Cycle AKA
    • Citric acid cycle or the KREB cycle
    • and then are completely dissassembled bu a series of chemical reactions
  122. Krebs Cycle
    • Carbon atoms and oxygen atoms are released as (CO2). 
    • Hydrogen atoms are shuttled to respirtatory enzymes in the inner mitochondrial membrane where  their elections are removed
    • The protons and electrons thus produced recombine with oxygen to from water(H2O)
    • During this process large ammounts of energy are released and used to make ATP.
  123. Aerobic metabolism of a common carbohydrate substrate, pyruvic acid, is quite efficient
    For each pyruvic acid molecule broken down in the TCA cycle , the cell gains 17 ATP molecules
  124. Pyruvic acid is provided through the process of
  125. Glycolysis
    • Is the breakdown of glucose to pyruvic acid in the cytoplasm of the cell. 
    • The ATP yeild of glycosis is much lower then that of aerobic metabolism
    • it can proceed in the absence of oxygen
  126. In resting skeletal muscle  the demanded for ATP is low so:
    • more than enough oxygen avaiable for the mitochondria to meet the demand and produce a suplus of atp
    • ATP is used to build reserves of CP and glycogen
  127. As the rate of mitochondrial ATP production rises, so does oxygen consumption.
    As long as sufficient oxygen is avaiable  the ammount of ATP provided by glycolysis is minimal
  128. In peroids  of peak activity when oxygen cannot diffuse into the muscle fiber fast enough to enable mitochondria to produce ATP:
    Mitochondrial activity provides about 1/3 of ATP needed and glycolysis become primary source.
  129. Glycolysis produces pyruvic acid faster then it can be used so...
    pyruvic acid levels rise in the cytoplasm and is converted to Lactic acid
  130. muscle fatique
    is caused bu the exhaustion of energy reserves or the buildup of lactic acid
  131. If muscle contractions at or below the maximum rate of mitochondrial ATP generation, the muscle fiber will function
  132. Recovery period
    conditions within the muscle care treturned to normal pre-exertion levels
  133. Lactic acid can be recycled during the
    recovery period
  134. when oxygen is available  latic acid can be converted into
    pyruvic acid
  135. Skipped muscle fibers
  136. Anaerobic endurance
    is the length of time muscle contractios can be supported by glycolysis and existing energy reserves of ATP and CP
  137. Aerobic endurance
    is the length of time a muscle can continue to contract while being supported by mitochontrial activities
  138. Terms that indicate postion, direction, or muscle fiber orientation
  139. Terms that indicate postion, direction, or muscle fiber orientation
  140. Terms that indicate postion, direction, or muscle fiber orientation
  141. Terms that indicate postion, direction, or muscle fiber orientation
  142. Terms that indicate postion, direction, or muscle fiber orientation
  143. Terms that indicate postion, direction, or muscle fiber orientation
  144. Terms that indicate postion, direction, or muscle fiber orientation
  145. Terms that indicate postion, direction, or muscle fiber orientation
    medial, middle
  146. Terms that indicate postion, direction, or muscle fiber orientation
  147. Terms that indicate postion, direction, or muscle fiber orientation
  148. Terms that indicate postion, direction, or muscle fiber orientation
  149. Terms that indicate postion, direction, or muscle fiber orientation
    Straight, parallel
  150. Terms that indicate postion, direction, or muscle fiber orientation
  151. Terms that indicate postion, direction, or muscle fiber orientation
  152. Indicate spedific regions
  153. Indicate spedific regions
  154. Indicate spedific regions
    auricle of ear
  155. Indicate spedific regions
  156. Indicate spedific regions
  157. Indicate spedific regions
  158. Indicate spedific regions
  159. Indicate spedific regions
  160. Indicate spedific regions
  161. Indicate spedific regions
  162. Indicate spedific regions
  163. Indicate spedific regions
Card Set
Medic 14 AP Chapter 7
AP 7