Phys Ch7 Exam2

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Phys Ch7 Exam2
2011-10-16 23:08:36
Phys Ch7 Exam2

Phys Ch7 Exam2
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  1. CNS consists of:
    brain, spinal cord
  2. PNS consists of:
    • Afferent signals (input)
    • Efferent signals (output)
  3. From PNS to CNS
    Afferent neurons
  4. From CNS to PNS
    Efferent neurons
  5. Neurons w/in CNS (most cells)
  6. 2 types of nerve cells
    • Neurons (Excitable cells) ~10%
    • Glial cells (Support cells) ~90%
  7. Part of neuron which contains nucleus & most organelles
    Cell body (soma)
  8. Part of neuron which receives incoming info
  9. Part of neuron which transmits elec impulses called action potentials
  10. Part of neuron where axon originates and action potentials are initiated
    Axon hillock
  11. Part of neuron that releases neurotransmitter
    Axon terminal
  12. Where 2 neurons or a neuron and an effector organ meet and communicate
  13. 3 types neuron ion channels
    • Leak channels
    • Ligand-gated channels
    • Voltage-gated channels
  14. Type of neuron ion channel which is always open, located throughout the neuron, responsible for resting membrane potential
    Leak channels
  15. Type neuron ion channel which open & close in response to ligand binding & which are often located on dendrites
    Ligand-gated channels
  16. Type of neuron ion channel which open & close in response to chg in mem potential & which are mostly located on axons
    Voltage-gated channels
  17. Difference in charge inside the cell relative to outside
    Membrane potential
  18. The voltage across the mem of a cell that is not transmitting a signal
    Resting membrane potential
  19. 2 factors which determine resting mem pot
    • Ion concentration gradients
    • Membrane permeability to these ions (ion channels)
  20. RMP is caused by ___ ___ in neuron membranes & is approx ____ mV
    • leak channels
    • -70
  21. An ion is at _______ when the electrochemical force is 0
  22. Na+, K+ concentrations
    Na+ high conc outside, K+ high conc inside
  23. Somatic vs autonomic PNS
    • somatic: can control via muscles
    • autonomic: cannot control (consists of para & symp nervous systems)
  24. What is the usually the charge of RMP and why? Is the cell at equilibrium at this time?
    • negative b/c more neg chrgs inside cell than out;
    • no
  25. What two factors determine resting membrane potential?
    • Ion concentration gradients
    • Membrane permeability to these ions (ion channels)
  26. At RMP:
    chemical force drives K+ ___ and Na+ ____
    electrical force drives K+ ___ and Na+ ____
    • out, in
    • in, in
  27. There are ___ leak channels for K+ and ___ leak channels for Ca+ in neurons
    (so neurons are more permeable to __)
    • more;
    • less
    • K+
  28. Membrane potential where chemical force and elec force are equal (electrochemical force=0)
    Equilibrium Potential (E)
  29. Net electrochemical force of K+ is ___ and Na+ is ____
    • out of cell
    • into cell
  30. At rest:
    small K+ leak (__ force, ___ permeability)
    small Na+ leak (___ force, ___ permeability)
    • low; high
    • high; low
  31. To maintain rmp of -70 mV, 3__ go out and 2__ go in so have a net of __ out
    • Na+, K+
    • +1
  32. When membrane potential veers from RMP it's due to ___
    ions passing thru gated channels
  33. What is diff b/w the way voltage-gated channels and ligand-gated channels open/close?
    • VG: open/close based on membrane potential
    • LG: open/close b/c ligand binds or doesn't bind to channel
  34. Shift from RMP to a more positive Vm
  35. Shift from RMP to a more negative Vm
  36. Return to RMP
  37. Diff b/w graded potentials and action potentials
    • Graded: small, travel short distances
    • Action: large, travel long distances
  38. Something that opens a gated channel (can be ligand or voltage gated) and causes a small chg in Vm, and which has variations in magnitude
    Graded potential stimulus
  39. How are graded potentials spread?
    By conduction (magnitude decays as potential spreads)
  40. Diff b/w inhibitory vs excitatory graded potentials
    • Prevent action potential (hyperpolarize)
    • Cause action potential (depolarize)
  41. What causes an action potential?
    If graded potential sums to reach threshold
  42. Large depolarization caused by opening of voltage-gated sodium channels which is a mechanism for cells to communicate
    Action potential
  43. Type of summation which consists of the same stimulus repeated over & over close together in time, causing a sum & response
    Temporal summation
  44. Type of summation which consists of diff stimuli and happen at the same time, causing a sum & response
    Spatial summation (like knocking on all walls at once)
  45. What type of cells generate action potentials?
    Excitable cells only
  46. Why does Na+ rush into cell so much faster than K+ after threshold is reached?
    Force is much higher on Na+
  47. What happens to Na+ and K+ channels after reaching threshold?
    • Sodium channels open rapidly then slowly close
    • Potassium channels slowly open
  48. Type of threshold which doesn't cause action potential
    Subthreshold depolarization
  49. Type of threshold which causes action potential & is above threshold
    Suprathreshold stimulus
  50. Concept that action potential from threshold & suprathreshold stimulus are same magnitude & therefore generate same response
    All-or-None Principle
  51. Explain how voltage-gated Na+ channels are opened
    Activation gate at top of channel is opened by a more positive mem potential (above threshold)
  52. Explain how voltage-gated Na+ channels are closed
    Inactivation gate at bottom of channel is already open at start of depolarization then closes during depolarization; remain closed until return to resting state (voltage and time dependent)
  53. Describe voltage-gated K+ channels
    Only one gate which is open or closed & which allows K+ ions to leave; opened slowly by depolarization
  54. Period of time following an action potential of decreased excitability & during which time an action potential cannot be produced
    Refractory period
  55. Diff b/w absolute & relative refractory period
    • Absolute: no stimulus can generate second action potential no matter how strong
    • Relative: occurs toward end of repolarization and which can allow a second action potential if stimulus is strong enough (as time goes on, a weaker stimulus can cause action potential)
  56. A means by which the central nervous system analyzes the content of a receptor; changes in stimulus intensity cause a change in the frequency of the impulses
    Frequency coding
  57. Site of axon where depolarization is taking place & when it is more pos inside cell, and neg outside cell, & which moves along to next site via conduction
    Region of depolarization (at the Nodes of Ranvier)
  58. Myelin nerve cells wrap themselves around ____
  59. Type of myelin-forming cell which is part of CNS and the cells of which form several myelin sheaths & myelinates sections of several axons
  60. Type of myelin-forming cells which is part of PNS and the cells of which forms one myelin sheath and myelinates one section of an axon
    Schwann cell
  61. Purpose of myelinated fibers when signals are conducted down an axon
    Keeps that part of axon "neutral" so that action potential "jumps" from one Node of Ranvier to next, w/out itself being affected. Allows for speed of signal
  62. What 2 factors increase the speed of conduction velocity?
    If myelin is present & the diameter of the myelin fiber
  63. 2 types of glial cells which are support cells of nervous system and form myelin
    Oligodendrocytes, Schwann cells