A&P Chapter 12 - Nervous

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A&P Chapter 12 - Nervous
2010-10-20 15:02:41
Chapter Nervous

A&P Chapter 12 - Nervous
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  1. central nervous system
    brain and spinal cord
  2. peripheral nervous system
    • nerves and ganglia outside of CNS
    • 2 divisions: somatic and autonomic
  3. somatic nervous system
    all nerves that control skeletal muscle
  4. autonomic nervous system
    • all nerves that control smooth muscle, cardiac muscle, and glands
    • 2 divisions: sympathetic and parasympathetic
  5. sympathetic nervous system
    emergency - fight/flight
  6. parasympathetic nervous system
    housekeeping - maintains normal
  7. neurons
    • highly specialized nerve cells that transmit action potentials
    • 3 groups: sensory, motor, association
  8. sensory neurons
    • aka ascending, afferent
    • carry APs from external and internal environment to spinal cord or brain
  9. motor neurons
    • aka descending, efferent
    • carry APs from brain or spinal cord out to effectors (muscles or glands)
  10. association neurons
    • aka interneurons, internuncial neurons
    • connect sensory and motor neurons
    • always located in brain or spinal cord
  11. dendrites
    groups of fibers that move APs toward cell body
  12. cell body
    • aka soma, perikaryon
    • contains nucleus and all organelles of the neuron
    • 3 unique structures: chromatophyllic substance, lipofuscin pigment, neurofibrils
  13. chromatophyllic substances
    • aka nissl body
    • rough ER of the neuron
  14. lipofuscin pigment
    fatty substance that gives neurone its yellow color
  15. neurofibrils
    protein tubes that gives cell body its shape
  16. axon
    long, slender projection of a neuron that moves APs away from cell body

  17. axon hillock
    cone shaped region that exits cell body
  18. initial segment
    end of axon hillock
  19. trigger zone
    impulses first start to move down axon
  20. axon collaterals
    • side branches of axon
    • always begins after trigger zone but before axon terminal
  21. axon terminal
    end of the axon
  22. neuroglia
    • aka glial cells
    • insulate, nourish, support, and protect neurons
    • 6 types:
    • CNS - oligodendrocytes, astrocytes, microglia, ependymal
    • PNS - schwann cells, satellite cells
  23. oligodendrocytes
    • CNS neuroglia
    • produce myelin in CNS
  24. myelin
    • fatty covering on axons
    • insulates and speeds conduction of APs
  25. astrocytes
    • CNS neuroglia
    • make neurotransmitters and maintain proper ion balances for impulse conduction
  26. microglia
    • CNS neuroglia
    • phagocytes that destroy bacteria
  27. ependymal
    • CNS neuroglia
    • contain cilia that help circulate CSF
  28. schwann cells
    • PNS neuroglia
    • produce myelin in PNS
  29. satellite cells
    • PNS neuroglia
    • help support cell bodies of peripheral axons
  30. membrane potential
    • more Na+ on outside of membrane
    • more K+ on inside of membrane
    • negative POPS on inside of membrane
    • -70mv charge - polarized
    • membrane is 100x more permeable to K+ than Na+
    • maintained by sodium-potassium pump, gated channels, and leakage channels
  31. sodium-potassium pump
    • pumps potassium outside to inside
    • pumps sodium inside to outside
    • 2 K+ move in, 3 Na+ move out
    • electrogenic (Na+/K+ move in unequal numbers)
  32. gated channels
    • open and close in response to a stimulus
    • more Na+ gated channels
  33. leakage channels
    • always open
    • more K+ leakage channels
  34. excitability
    • neurons ability to respond to a stimulus and convert the stimulus into an AP
    • if stimulus is threshold, membrane's permeability to Na+ increases because stimulus opens Na+ channels
  35. stimulus
    any condition in the environment that is capable of changing resting potential to some other number
  36. depolarization
    • change in resting potential from -70 to +30
    • stimulus opens Na+ gates
    • stimulus turns off Na+/K+ pump
    • stimulus makes membrane impermeable to K+
  37. Hodgkin's cycle
    • once depolarization hits -55, stimulus no longer required because AP becomes self-generating due to ion movement
    • positive feedback loop
  38. repolarization
    • +30 to -70
    • Na+ gates begin closing
    • K+ gates begin opening
  39. action potental
    a complete depolarization and repolarization of the membrane
  40. absolute refractory period
    • period of time when a second stimulus cannot generate an AP because sodium gated channels are already open
    • occurs during depolarization
  41. relative refractory period
    • period of time where sodium gated channels are closing and potassium gated channels are opening
    • occurs during repolarization
    • a super-threshold stimulus can reopen Na+ gates and generate a 2nd AP
  42. super-threshold stimulus
    an extremely strong stimulus that can reopen Na+ gates during refractory period and generate a 2nd AP
  43. sub-threshold stimulus
    • an extremely weak stimulus that is not capable of depolarizing to -55
    • produces slight hypopolarization followed by repolarization
  44. all or none
    • a threshold stimulus always generates an AP
    • AP moves from trigger zone to axon terminal at constant and maximum strength
  45. continuous conduction
    AP moves along unmyelinated neuron from point to point
  46. saltatory conduction
    • AP moves along myelinated neuron
    • myelin acts as insulator (APs cannot travel through it)
    • AP depolarizes and repolarizes at Nodes of Ranvier (neurofibril nodes)
    • faster and more efficient
    • cell uses less energy
  47. synapse
    • place where 2 neurons come together or where a neuron meets an effector
    • 2 types: electrical and chemical
  48. electrical synapse
    • cardiac tissue
    • embryo (nervous system not developed)
  49. chemical synapse
    neurotransmitters released to bridge gap caused by synapse
  50. neurotransmitters
    • group of specialized chemicals that allow neurons to communicate with each other or with an effector
    • must be located in an axon terminal
    • must be able to open gated channels
    • must be able to be eliminated after it performs its job
  51. excitatory NT
    • opens Na+ channels
    • lower the resting potential of the post-synaptic dendrite from -70 to a number closer to threshold
    • makes it easier for future impulse conduction
  52. inhibitory NT
    • opens K+ channels
    • hyperpolarize the membrane to make it more negative than -70
    • makes it more difficult for future impulse conduction
    • *how pain relievers work
  53. PNS NTs
    • acetylcholine (Ach)
    • norepinephrine (Ne)
  54. convergent neuron circuit
    • several pre-synaptic neurons converge with one post-synaptic neuron
    • ex: NMJ
  55. divergent neuron circuit
    • one pre-synaptic neuron synapses with many post-synaptic neuron
    • ex: CNS
  56. reverberating neuron circuit
    • 1st neuron synapses with 2nd which synapses with 3rd
    • axon collaterals from 3rd go back to synapse with a previous neuron
    • ex: respiratory
  57. summation
    • many axon terminals converge and release NT to generate an AP
    • 2 types: spatial and temporal
  58. spatial summation
    rapid depolarization to threshold because axon terminals release NTs at exact same time
  59. temporal summation
    gradual depolarization to threshold because axon terminals release NTs one after the other