Nervous system

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cquinns731
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109512
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Nervous system
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2011-10-19 22:20:55
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nervous system
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  1. functions of nervous system
    •Stabilizes intrinsic conditions

    -blood pressure

    -O2 and CO2 content

    -pH

    -blood glucose levels

    -hormone levels


    •Regulates behavioral patterns

    -feeding, reproduction, defense, interaction with others
  2. afferent and efferent?
    afferent = periphery to CNS

    efferent = CNS to periphery
  3. what are the cells in the nervous system?
    • neurons
    • glial cells
    • vasculature
  4. neurons?
    • vary in length
    • numerous long processes
    • receive stimuli and conduct electrical impulses
  5. glial cells in CNS?
    neuroglia
  6. glial cells in PNS?
    shwann cells or satellite cells
  7. fxn of glial cells?
    • severl types
    • short processes
    • non conducting cells
    • support aand protect neurons
  8. vasculature
    blood brain barrier
  9. break neurons down functionally:
    • sensory neurons: Somatic afferent - pain, temperature, touch, pressure, proprioperception
    • Visceral afferent - pain and other sensations (mucous membranes, glands and blood vessels

    motor neurons: somatic efferent: voluntary impulses to skeletal muscles, visceral efferent: involuntary impulses to smooth muscle, cardiac conducting cells and glands

    internuerons: network between sensory and motor neurons, greater than 99% of neurons, mammalian evolution
  10. which part of neuron has clear cytoplasm
    axon ( receives and transmits info)
  11. what part receives stimuli?
    dendrites
  12. what are dendrites covered in?
    snypatic endings of other neurons

    processes of glial cells
  13. what is a nissl body?
    - stack of rough ER in the cell body
  14. what is ganglia?
    collection of nerve cell bodies outside CNS
  15. main types of neurons (structural)?
    • bipolar - 1 axon, 1 dendrite (limited to certain neurons in eye and ear)
    • multipolar - lots of dendrites and one axon (motor neurons)
    • pseudounipolar- 2 axonal branches - one goes to the CNS and one extends to the PNS (sensory neurons!)
  16. other name for cell body?
    perikaryon - contains nucleus and organelles
  17. what are the 2 types of synpases?
    1) chemical - bind to receptors at postsynaptic cleft, so then ion channels open up, somtimes secondary messengers,


    2) electrical - found in invertebrates, direct movement of ions from one to another
  18. what is a bouton terminal?
    a presynaptic knob - end
  19. which molecules are involved in a synapse?
    • synaptic vesicles
    • v snare
    • t snare
    • synaptotagmin
  20. v snare?
    vesicle bound proteins
  21. t snare
    post synaptic membrane bound proteins
  22. mechanism of how neurotransmitters fuse with membrane
    presynaptic membrane depolarization - brief opening of Ca channels - exocytosis of synapic vesicles - release of neurotransmitter - neurotransmitter reacts with receptors - promotes postsynaptic depolarization - membrane retrieval by coated vesicles
  23. synaptotagmin
    binds calcium and helps membranes come together
  24. what do v snare, t snare, and synaptotagmin do?
    they act like a zipper zipping the two membranes together
  25. explain how botox works
    and what is the neurotoxin?
    bochilism neurotoxin = bacterial protein causes paralysis and death

    • there are 2 polypeptides:
    • 1) binds to membrane protein of synapse of motor neurons (muslce) allowing protein 2 to get into the cell. 2 is a protease that chews up VSNARE (so neurotransmitters cant release) causing paralysis
  26. what are the 3 ways that neurotransmitters are removed?
    • enzymatic breakdown
    • diffusion
    • endocytosis
  27. what happens to sodium gated channels when neuron is stimulated?
    na channels open up!! depolarization (gradient set up by the NAK ATPase pump
  28. what are the voltages that occur?
    normally it is at -65 mV but then sodium rushes into the cell all the way up to 30mv (action potential!) and then stops
  29. how do you get back to -65?
    voltage gated Na close and potassium channels open up (K moves OUT of the cell)
  30. how do local anesthetics work?
    hydrophobic molecules that bind to sodium channels, bind to open sodium channels (ones where neurons are firing)

    it is reversible
  31. what are some inhbitory neurotransmitters?
    how do they work?
    • GABA
    • glycine

    THEY OPEN ANION CHANNELS (make it negative) - they HYPERPOLARIZE the cell (make it go lower than -65 mV
  32. propofol?
    increases effects of GABA, also may block sodium channels... how michael jackson died :( thrillller
  33. How is myelin produced?
    what is it and its function?
    • produced by:
    • - oligodendrocyes (CNS)
    • - shwann cells (PNS)

    myelin = 80% lipid, provides electrical insulation of neurons, makes impulse travel down axon quicker
  34. how do shwann cells wrap around axon?
    • modified plasma membrane of shwann cell winds and wraps around the neuron a bunch of times
    • membrane has more lipids than normal

    diff neurons have diff thicknesses
  35. what is neuregulin?
    growth factor secreted by axon that regulaes thickness of myelin sheath (on axolemma)
  36. what is the name of the location with no myelin?
    Node of Ranvier!! (where 2 shwann cells meet)

    voltage reversal jumps from node to node
  37. what is important at node of R's?
    lots of K and Na channels so ACTION POTENTIALS OCCUR HERE!

    otherwise myelin sheath would be covering it up
  38. what about unmyelinated neurons?
    nodes or R's?
    shwan cell takes it and hugs it once, doesnt wrap around a ton

    no nodes! na channels alll along the neuron
  39. what are glia? and what are the 4 types that are in the CNS?
    • oligodendrocytes: myelination in CNS
    • astrocytes - morphologically heterogeneous, physical and metabolic support for neurons, most numerous!
    • microglia- phagocytosis
    • ependymal cells : line ventricles of brain and central canal in spinal cord
  40. whats different about myelin sheaths in the CNS?
    - unmyelinated - naked!!

    • the ones that are: are wrapped around by oligodendrocytes (which can myelinate several axons)
    • organization of myelin sheath is much more complicated
    • larger nods of ranvier - more efficient saltatoy conduction
  41. difference between oligodendrocytes and swhann cells?
    swhann wrap around one axon, oligodendrocytes wrap around multiple axons
  42. what are the proteins involved in myelin sheath? fxn?
    Proteins= PO and MBP and PMP 22

    hold membranes together
  43. what is multiple sclerosis?
    • demyelinating disease
    • results in neuro defecits, loss of cutaneous sensation, lack of muscle coordination and movement, loss of bladder and bowel control

    myelin sheath destroyed by an unknown mech

    production of irregular multiple plaques

    possibly an autoimmune disorder - increased antibodies against MBP (myelin basic protein)
  44. what is shape of phagocytic cells?
    microglia?
    • small elongated cells with short irregular processes
    • involved in inflammation and repair in adult CNS
    • act like immune system cell!
  45. microglial cells and HIV?
    • aids dementia complex is caused HIV infection of the CNS
    • evidence indicates the microglia are infected by HIV
  46. what are astrocytes?
    shape?
    numerous?
    2 classes? and how do the classes differ?
    • largest, most numerous of neuroglial cells
    • star shaped

    • 2 types: similar in fx, diff shape
    • 1) protoplasmic astrocytes
    • - many short branched processes
    • more prevalent in grey matter
    • 2) fibrous astrocytes
    • - few long straight skinny processes, white matter, GFAP more numerous, 80% of adult primary brain tumors are this
  47. how is star shape maintained
    • by IF protein (glial fibrillary acid protein)
    • bundles of intermediate filaments
  48. what are the function of astrocytes?
    • support and bind neurons
    • controls movements of molecules to and from neurons
    • regulates (buffers) K+ concentrations in brain
    • influence neuronal activity
    • blood brain barrier
    • forms a network
    • they fully cover everything!!!
    • control chemical environment (eat up old neurotransmitters)
  49. ependymal cells
    • line the ventricles of brain and spinal cord
    • it is an epithelial layer
    • some can become secretory - choroid plexus - makes cerebral spinal fluid
  50. look at figure in the book (slide 36) to see how it all fits together
  51. peripheral nerves - where can cell bodies be found?
    how many neurons and where does it go?
    which kind of root?
    which kind of axon?
    cell bodies - in CNS or peripheral ganglia

    1 neuron (pseudounipolar) connects receptor through a sensory ganglion to the spinal cord of brain (dorsal roots)
  52. sensory ganglia
    foudn in DRG (dorsal root ganglia), otuside each nerve root of spinal cord
  53. motor neurons

    how many neuron?
    what kind?
    ventral or dorsal?
    cell bodies in CNS, peripheral nerves travel to target skeletal muscle

    • single neuron
    • somatic efferetn
    • ventral!
  54. visceral efferent (autonomic) neurons?
    how many neurons?
    presynapic neuron (CNS to peripheral ganglia)

    postsynaptic neuron (ganglia to target system (smooth muscle, cardiac muscle, and glands)
  55. what are the 3 types of connective tissue that surround nerves?
    • endoneurium - around nerve fibers (collagen is parallel to axon)
    • perinurium - specialized CT, around each nerve fascile, active diffusino barrier has controlling transporters
    • epinurium - dense irregular connective tissue, surrounds a nerve
  56. check out slide 41
  57. structure of spinal cord
    • grey matter on inside
    • white matter on outside
    • dura mater, arachnoid, pia mater
    • dorsal root vs. ventral root
  58. structure of brain?
    what does grey matter on outside form?
    • grey matter on outside, white in middle
    • grey on outside forms CORTEX
  59. diff between white matter and grey matter?
    • white = myelinated axons (functionally related bundles of axons, not randomly distributed
    • grey = cell bodies
  60. whats the equivalent of ganglia (PNS) in the CNS?
    nuclei!!

    functionally related clusters of cell bodies in CNS (diff from ganglia
  61. what are meninges? function?
    meninges = 3 membranes (connective tissue) surrounding brain and spinal cord

    starting from outside:

    • dura mater - tough mother, dense CT, continuous with perostium of skull!
    • arachnoid - sheet like extensions, web like, in subarachnoid space is like an extra cushion - thespaces is cerebral fluid,
    • pia mater - right on top o CNS (tender mother), continuous with perivascular sheath (blood vessels go down into brain and the pia mater lines those sheaths also) pia mater also lies on endfoot processes of astrocytes
  62. explain blood brain barrier:
    • Blood brain barrier = physical barrier between blood vessels
    • and vast majority of CNS, stops many substances from crossing!

    • Blocks all molecules except those can cross by lipid diffusion
    • (O2 can cross, steroids can cross, alcohol, CO2, drugs, heavy metals




    • All sorts of active transport proteins – everything that gets
    • to neurons have to be transported (glucose! Amino acids, vitamins, and even)
    • across endothelial cells, into astrocytes, then to neuron
  63. what makes it tight?
    Tight junction, really complex in epithelia of capillaries

    • Association
    • of basal lamina of endothelial cells with end foot processes
  64. aqua porins?
    channel proteins for water, all alon blood brain barrier

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