MS- Neurophysiology.txt

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MS- Neurophysiology.txt
2015-03-02 18:09:20
musculoskeletal neurophysiology

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  1. Information carried by nerves is coded by __________; therefore, _______ and ________ are invariable.
    frequency; amplitude; duration
  2. To increase strength of contraction, the signal does not become larger, but the __________ becomes greater.
    frequency of impulses
  3. The voltage that exists b/w the inside and the outside of the cell, across the cell membrane.
    membrane potential
  4. With respect to resting membrane potential, we assign a ________ value to the interior of the cell with respect to the outside of the cell.
  5. The voltage at which there is no net diffusion taking place.
    equilibrium potential
  6. The equation that relates elecrical gradient and chemical gradient to calculate the membrane potential in a cell.
    Nernst equation
  7. The equilibrium potential is totally dependent on the ___________ of the ___________.
    concentration gradient; permeable ion
  8. (Membrane semipermeable to K+ only) Net diffusion is K+ down its ___________ gradient until equilibrium is reached, at which time the tendency for K+ to diffuse down its _________ equal its tendency to diffuse the other way, down its _________.
    concentration; concentration; electrical
  9. _______ plays a major role in the membrane potential of most animal cells.
  10. ________ is passively distributed across the cell membrane according to the potential established by the diffusion of ________ out of the cell, creating a negative charge from the fixed anions within the cell.
    Chloride; potassium
  11. _________ maintains electroneutrality for sodium that is outside the cell.
  12. The equation that considers not only the concentration ratios of sodium, chloride, and potassium, but also takes their respective permeabilities into account in the calculation of equilibrium potential.
    Goldman equation
  13. The Na-K ATPase pump carries ________ back into the cell while removing _______ from the cell.
    potassium; sodium
  14. Electrogenic pumping of the Na-K ATPase pump occurs when the pump exchanges _________ for ______, resulting in a net loss of __________, generating a current.
    3 sodium ions; 2 potassium ions; positive sodium ions
  15. Electrogenic pumping of the Na-K ATPase pump contributes to the __________ of the cell.
    negative interior
  16. What are the 4 factors that describe the genesis of membrane potential?
    concentration gradient for K+ from inside to outside, the high permeability of K+ in the resting membrane, the fixed anionic charges within the cell, the Na-K ATPase pump
  17. The membrane potential of excitable cells.
    resting membrane potential
  18. Membrane potential during which the membrane actively responds with a conducted impulse, usually resulting in some action.
    action potential
  19. Term describing the fact that even during the inactive or resting condition, ions are constantly leaking down their concentration gradients.
    steady-state potential
  20. Location where the release of a neurotransmitter substance acts to stimulate the receptors.
  21. The ease with which the events leading from the application of the stimulus to the initiation of the action potential take place.
  22. When a stimulus is applied, the membrane potential is displaced from its normal level of __________.
  23. If current is added to the membrane potential, it becomes more ___________; if current subtracts from the membrane potential, it becomes more _________.
    negative (hyperpolarization); positive (depolarization)
  24. When the current is depolarizing and the stimulus is adequate to elicit an action potential, _________ has been reached and ___________ has occurred.
    threshold; excitation
  25. The point at which activation of the membrane takes place, resulting in the regenerative phases of an action potential and a conducted impulse.
    threshold level
  26. Stimuli that fail to elicit an action potential.
  27. Passive changes in the membrane, which are a result of a subthreshold stimulus.
    local response
  28. Generator potential, synaptic potential, and electrotonic potential are examples of __________.
    local responses
  29. The greater the voltage difference b/w the threshold and the resting potential, the _____ excitable the tissue because...
    less; a larger stimulus would be required to reach threshold level
  30. Hypocalcemia results in the membrane becoming ___________, threshold is ________, and excitability ________.
    destabilized; lowered; increases
  31. Hypercalcemia results in the membrane becoming __________, threshold is _________, and excitability _________.
    more stabilized; increased; decreases
  32. Hyperkalemia _________ the resting potential by ________ the gradient for potassium to diffuse out of the cell and _________ excitability.
    lowers; decreasing; increases
  33. Hypokalemia __________ resting potential, and ________ excitability because the gradient for potassium to diffuse out of the cell is _________.
    increases; decreases; increased
  34. If hyperkalemic depolarization is severe, the membrane remains depolarized, is unable to be __________, and may become ______ excitable.
    reactivated; less
  35. Condition in which the membrane remains inexcitable due to persistent or gradual depolarization, such as in the case of severe hyperkalemia.
  36. Activation of the membrane takes place when... (2)
    threshold is reached, ion channels are opened to reduce the membranes resistance to the passage of ions
  37. Change in membrane resistance.
    change in conductance (g)
  38. Ion channels have the property of selectivity and undergo a pattern of ______________.
  39. Sodium channels are responsible for the ________ of the membrane.
  40. Potassium channels are responsible for the __________ of the membrane.
  41. Sodium and potassium channels are _____-gated.
  42. Channels whose activation/opening is dependent upon a change in the voltage of the membrane, which occurs with a depolarizing stimulus.
  43. Voltage-gated channels are activated/opened with a ________ stimulus.
  44. As soon as the voltage inside becomes less _______ (__________), some voltage-gated sodium channels begin to activate/open.
    negative (depolarization)
  45. A sodium channels open due to depolarization, more sodium ions rush in, causing the inside to become less negative and more depolarized to its threshold. This is known as a process of __________.
    positive feedback
  46. Rapid sodium influx drives the membrane potential toward and even past _______; this rapid depolarization increases the __________ so that sodium conductance may increase up to 10,000 times the resting value.
    zero (to some positive number); membrane's permeability to sodium
  47. What 2 things occur to immediately oppose the sudden influx of sodium and depolarization of the membrane?
    • -Sodium channel activation is short-lived
    • -Before action potential begins,concentration and electrical gradients for sodium are oriented inward; as the membrane depolarizes, the inside of the cell briefly becomes positive, and the electrical gradient is abolished
  48. At the same time the depolarization starts to open sodium channels, it also opens __________, which also tend to oppose the sodium channel activation.
    potassium channels
  49. Voltage-gated potassium channels open _________ than sodium channels and are open for a _______ period of time.
    slower; longer
  50. During repolarization, potassium enters the cell at a _______ rate than sodium and for a _______ period of time.
    slower; longer
  51. The outward movement of potassium carrying positive charges restores the __________ to its original ___________, which also brings about ___________.
    membrane potential; negative resting value; sodium channel reactivation (ready to open again)
  52. Potassium efflux is a process of __________.
    negative feedback
  53. Every time an impulse passes along the surface of an excitable cell, the changes in membrane conductances underlying an action potential causes a slight gain of __________ and loss of _________. The __________ operates in the background to restore the gradients.
    intracellular sodium; intracellular potassium; Na-K ATPase membrane pump
  54. Hypernatremia and hyponatremia result in changes in the _______ and _______ of _______________.
    rate; amplitude; depolarization
  55. Because the velocity of impulse conduction is directly dependent on the rapid phase of ___________, conditions resulting in ___________ can alter impulse conduction.
    depolarization; sodium imbalance
  56. Conditions of ________ alter resting membrane potential, excitability, and normal repolarization of the membrane, thus lengthening the amount of time the membrane is refractory (cannot conduct an impulse).
    potassium imbalance
  57. Undiminished in size over a distance.
  58. Frequency coding is an ________ signal that is the same ______ every time.
    on-off; size
  59. The energy to maintain a signal over the relatively long distances of very thin nerve fibers.
    membrane potential
  60. When an impulse passes over the surface of a cell, there is a wave of _______ on the surface of the cell and a wave of _______ inside the cell.
    negativity; positivity
  61. The passive flow of positive charges depolarizing the membrane, causing the membrane directly in front of the impulse to become less ___________ until threshold is reached and _____________, allowing the regenerative depolarization-repolarization action potential cycle to continue.
    negative; sodium channels open
  62. The speed (velocity) with which an impulse is conducted is determined by the....
    passive flow of ionic current in the local circuit (depolarization-repolarization cycle occurring repetitively in the forward direction)
  63. Factors that control the passive flow of charges in the local circuit (depolarization-repolarization in the forward direction, conducting an impulse).
    separation of charges gives rise to voltage difference which drives the current, the ease with which these charges can flow forward in the local circuit (depends on cross-sectional diameter of the axon)
  64. As axon diameter increases, the resistance _______ and local flow can depolarize adjacent membrane areas _________.
    decreases; more quickly
  65. If a membrane is better insulated and directs flow forward, local flow and depolarization are ______ and __________ is increased.
    faster; conduction velocity
  66. Myelinated nerves conduct ______ than unmyelinated nerves because....
    faster; they are more well insulated and direct flow forward
  67. Nerve fibers which are enveloped with special glial cells containing myelin, giving them better insulating qualities and faster conduction velocity.
    Schwann cells
  68. The myelin of nerves is interrupted at intervals, allowing expose, uninsulated cell membrane areas, which are called ______________.
    nodes of Ranvier
  69. When an impulse spreads along a myelinated nerve, the nodes of Ranvier __________ readily, providing a ____________ driving force and added insulation b/w nodes forces the rapid flow of charges to ________________.
    depolarize; large voltage difference; depolarize the next adjacent node
  70. Two important properties which can be used to assess normal function in excitable tissues are...
    conduction velocity and maximal frequency of response as related to refractoriness
  71. Movement of an impulse jumping from node to node for more rapid conduction in a myelinated nerve.
    saltatory conduction
  72. _____________ requires that the time be determined that it takes for an impulse to be conducted over a known distance.
    Conduction velocity
  73. When determining refractoriness, if the stimulus producing the second impulse is maximal in strength, then the shortest interval would be the _____________.
    absolute refractory period
  74. hen determining refractoriness, if the stimulus is of just threshold strength, then the shortest interval would be the _____________.
    total refractory period
  75. The time difference b/w the absolute refractory period and the total refractory period.
    relative refractory period
  76. A stimulus of greater than threshold strength can elicit a response during the _________.
    relative refractory period
  77. Refractory periods prevent excitable tissue from...
    responding to excessive rates of stimulation which might result in ineffective signal transmission.
  78. Both excitation-secretion coupling and excitation-contraction coupling are ________-mediated processes.
  79. Common features of neurotransmission at all chemical synapses in animals. (5)
    presynaptic mechanisms for neurotransmitter synthesis, neurotransmitter storage, neurotransmitter release, a post-synaptic mechanism for neurotransmitter receptor signal transduction, and a mechanism for neurotransmitter termination
  80. The neurotransmitter at the neuromuscular junction.
    acetylcholine (ACh)
  81. Acetylcholine is synthesized within the prejunctional terminal from _______ and ________ by the enzyme choline acetyltransferase.
    acetyl-CoA; choline
  82. Choline acetyltransferase is produced in the __________ and is transported down the axon to the terminal by __________.
    cell body; axoplasmic transport
  83. When an impulse originating in the CNS reaches the nerve terminal, the prejunctional membrane is rapidly _________ by _________.
    depolarized; sodium influx
  84. When the prejunctional membrane is depolarized (as the impulse from the CNS is conducted to the nerve terminal), voltage-gated _________ open, and ________ enters the cytoplasm, causing...
    calcium channels; calcium; vesicles containing ACh to exocytose their contents into the junctional cleft
  85. When ACh is released into the junctional cleft, it rapidly diffuses toward the _________, which has __________ receptors, which are _______- gated channels, associated with ion channels.
    end-plate; cholinergic nicotinic; ligand
  86. When ACh binds to the ligand-gated channels on the motor end-plate, the end-plate is ___________ due to __________, initiating a __________.
    depolarized; sodium influx; contraction
  87. The enzyme that terminates the action of ACh is ____________; it hydrolyzes ACh to ________ and _________.
    acetylcholinesterase; acetic acid; choline
  88. Hypocalcemia can cause paralysis because...
    there is insufficient calcium available to trigger adequate ACh release.
  89. Curare, a neuromuscular blocking drug, results in paralysis because it blocks ____________.
    nicotinic receptors
  90. Inhibitors of acetylcholinesterase allow the ________________, which leads to continual ________ of the end-plate and _______.
    accumulation of ACh; depolarization; paralysis
  91. Myasthenia gravis is an autoimmune disease that results in the destruction of ____________.
    nicotinic receptors
  92. The functional unit of a striated muscle.
  93. The sarcomere is the area lying between adjacent _______, which...
    Z-diss; shortens upon contraction
  94. The sarcolemma in the muscle cell membrane, which conducts ________ along the cell surface.
    action potential
  95. __________ invaginate the cell surface and communicate with the extracellular fluid, carrying the electrical signal to the sarcomere.
  96. The _________ surrounds each myofibril and controls the movement of calcium within the muscle.
    sarcoplasmic reticulum
  97. Calcium is sequestered in the ______ after it is released from the terminal cisternae.
    lateral sacs
  98. The sarcomere contains myofilaments of ________ surrounded by _______ in a hexagonal array.
    myosin; actin
  99. Each actin filament is attached to the _________, producing the light area called the ______.
    Z-disc; I-band
  100. The myosin filaments are attached to the ______.
  101. The H-band, centered around the M-line, contains only ________.
  102. The area where actin and myosin overlap.
  103. Troponin and tropomyosin respond to changes in ________.
    intracellular calcium concentration
  104. The cross-bridges on the head of each myosin molecule contain _________, which hydrolyzes _____, and the released energy is used to...
    ATPase; ATP; silde the actin molecule along the myosin molecule to shorten the sarcomere (muscle contraction)
  105. What are the 8 steps in muscle contraction?
    • 1. end plate potential
    • 2. conduction of muscle action potential
    • 3. inward spread of depolarization along T-tubules
    • 4. release of Ca2+ from sarcoplasmic reticulum
    • 5. diffusion of Ca2+ to troponin binding site
    • 6. binding of Ca2+ to troponin uncovering actin binding sites
    • 7. formation of cross-bridges between actin and myosin
    • 8. sliding of filaments and shortening of sarcomere
  106. What are the 3 steps in muscle relaxation?
    • 1. Ca2+ pumped back into sarcoplasmic reticulum
    • 2. release of Ca2+ from troponin
    • 3. detachment of actin and myosin cross-bridges
  107. A contraction when the external length of the muscle does not shorten during contraction.
  108. A contraction when the external shortening occurs while tension remains approximately constant.
  109. When the load imposed by a muscle exceeds the force developed by the muscle, ________ is minimal and little or no _______ is detected.
    velocity; movement
  110. The length-tension relationship is based on the amount of....
    overlap between actin and myosin filaments
  111. The greater the degree of overlap between myosin and actin, the greater the number of _______ and thus, the greater the ____________.
    cross-bridges formed; force of contraction
  112. The velocity of muscle shortening is related inversely to the _______ so that as the speed at which actin and myosin slide past each other increases, the ________________ that can be formed decreases.
    force; number of cross-bridges
  113. The force developed the stretching.
    passive tension
  114. Force which results from cross-bridge formation and sarcomere shortening.
    active tension
  115. The tension developed each time the muscle is stimulated to contract at a new length.
    total tension
  116. The velocity of muscle shortening is inversely related to the...
    force generated by the imposed load.
  117. Purposeful muscle contractions appear as smooth, sustained, forceful contractions because of... (3)
    asynchronous firing of motor units, summation of motor units, tetany
  118. When the frequency becomes so fast that no relaxation occurs between contractions, and the contractions become fused.
  119. As the demand for greater force of contraction is required of the muscle, more individual motor units containing more fibers per unit are made to contract. As individual motor units contract, they do so ___________ so that the contraction becomes smooth and sustained.
  120. ADP is rephosphorylated to ATP by the transfer of phosphate from __________.
    creatinine phosphate
  121. The total amount of energy available from creatinine phosphate must be replenished by _______ and _________.
    glycolysis; oxidative phsophorylation
  122. Muscle fatigue closely parallels depletion of _________.
    muscle glycogen
  123. Red muscle contains the oxygen-storing protein ________; it is adapted for...
    myoglobin; aerobic metabolism and activity requiring endurance
  124. White muscle contains ________; it is adapted for...
    glycogen; rapid, anaerobic metabolism, fast, powerful contractions but fatigues readily