Neural Control Mechanisms

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skhan11
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200886
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Neural Control Mechanisms
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2013-02-20 23:29:32
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Physiology
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Physiology
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  1. Afferent
    (sensory) Carry impulses toward CNS
  2. Efferent
    carry impulses away from CNS
  3. Somatic
    to skeletal muscles - consciously controlled
  4. PNS consist of:
    consists of the nerves and ganglia outside of the brain and spinal cord
  5. Autonomic Nervous System:
    to organs, smooth muscle, cardiac muscle, not consciously controlled.
  6. ENS = _____
    Digestive System
  7. Glial supporting cells:
    ____ brain cells.... occupy... ____
    10% brain cells r neurons occupy 50% extns
  8. List some glial cells
    • Astrocytes
    • Schwann cells
    • Oligodendrocytes
    • Microglia
    • Ependymal cells


    ASOME
  9. ASTROCYTES (GLIAL CELL)
    Forms blood brain barrier

    Regulates extracellular fluid around neurons
  10. Oligodendrocytes
    Responsible for myelin formation in CNS.
  11. Schwann Cells
    Non-neural cell that forms myelin sheath in PNS.
  12. Microglia
    type of glial cell that acts as macrophage
  13. Ependymal cells
    glial cell that lines internal cavities of the brain and produces cerebrospinal fluid
  14. Type of neuroglia in CNS:
    • Astrocytes
    • Oligodendrocytes
    • Ependymal Cells
    • Microglia
  15. Type of neurological in PNS:
    Satellite cells & Schwann cells

    1 axon may have as much as 500
  16. Neural growth and regeneration steps:
    • Precursor stem -->
    • Differentiate ->become Neurons & Glial Cells
    • Neurons Migrate ->
    • Processes become dendrites & axon
    • 50-70% Apoptosis
    • Regeneration Occurs
  17. Functional anatomy of neuron:

    Dendrite
    Axon (Nerve Fiber)
    Axon Hillock
    Collateral Axon
    Node of Ranvier
    Axon Terminal
    BranchSchwann Cell
    Oligodendrocyte
    Neurilemma
    Myelin Sheath
    Soma
    Terminal
    End Knob
    BulbTrigger Zone
    • Dendrite
    • Axon (Nerve Fiber)
    • Axon Hillock
    • Collateral Axon--Node of Ranvier--Axon Terminal Branch--Schwann Cell----Myelin Sheath--Soma--Terminal End Knob--Bulb--Trigger Zone
  18. Definition of Synapses
    Chemical + Electrical
  19. What is the synaptic cleft usually bridged by?
    Neurotransmitters
  20. Functional Clasification of neurons (3)
    sensory, motor, and interneurons

    • sensory = afferent
    • motor:
    • interneurons:
  21. What three broad classes of channels do the neural cell membrane contain?
    • Ligand-gated channels
    • Voltage-activated channels
    • Leak Channels
  22. Axoplasmic Flow
    aka
    Axonal Transport
    The directed transport of organelles and molecules along nerve cell axons.

    • can be from the cell body
    • or
    • towards the cell body
  23. Grey Vs White Matter
    • Grey Matter          vs            White Matter
    • -Neural Cells    *Axons connect 2 NeuralCells
    • -Forms Cerebral Cortex *White kuz Myelin S.
    • -Thalamus/Ganglia Also GM *Glia cells
    • -Makes up Outer Surface * Inner Parts
  24. Innervation
  25. Electrical potential is the difference.....
    Measured in?
    difference in charge and is measured in mV
  26. The movement of electrical charge is called:

    Hindrance of electrical charge movement is called:
    • Current (flow)
    • Resistance
  27. Potential is the difference.......
    Difference between two amount of charges influenced by # of charged particles and how close they are
  28. Equilibrium potential for an ion is described by the
    NERST EQUATION

    E=RT/zF in Cout/Cin
  29. Resting membrane potential
    Uneven distribution of ions across the membrane caused by 3 things
  30. What are some things that cannot pass out of the membrane?
    • Negatively charged proteins
    • Organic Phosphates
    • Bicarbonates
    • Glutamate
  31. What is determined by permeability of the membrane?
    • Electrical charge across membrane
    • or
    • Magnitude of resting membrane potential
  32. What are the four channels in neurons we are most worried about in this class?
    • NA+ K+ CA2+ CL-
    • CHANNELS
  33. What is an action potential and what causes it?
    A nerve impulse conducted on an excitable membrane, takes the movement of only a few ions to create large change in potential.
  34. What causes an Action Potential?
    • -Nerve impulse on excitable membrane
    • -Stimulus that causes depolarization  to                              threshold.
    • -Takes generation potenrtial of ~15-30mV
    • -~55-45mV, Stimulates opening NA+ gates
    •                 (ions rush in aka influx)
    • -Inside becomes positive so NA+ gates open
    •                (positive feedback loop)
    • NA+ gates start closing(K/NA ATPase Pump)
    • -K+ voltage gates open later
    •                 (neg feedback loop)
    • -Once threshold surpassed the AP full sized
    • -Re polarization
    • -K+ gates start closing
    • -Hyperpolarization
    • -Refactory Period
    • -Resting Potential
  35. Graded Potential are... that occur mostly in....

    Characteristics include....
    Depolarizations or Hyperpolarizations that occur in dendrites,

    • Characteristics of graded potential
    • -Exitatory or inhibatory
    • Excitatory=neurotrans+mem.recep. stimulate opening of NA+ ligand-dependent channels causing local current flow.
    • Current flow --> Trigger Zone
    • Opens Na+ Voltage-dep gates if threshold
  36. Absolute Refractory Period
    vs
    Relative
    Refractory Period
    •  Absolute Refactory period:
    • is the interval during which a second action potential absolutely cannot be initiated, no matter how large a stimulus is applied.

    • Relative Refactory Period:
    • is the interval immediately following during which initiation of a second action potential is inhibited but not impossible.
  37. Xyclocaine or novacaine prevent....
    Prevent NA+ gates from openning!
  38. Propagation or conductance of AP
    • -Depolarization in one area stimulates depolarization in adjacent area.
    • -Direction is away from the area of stimulus
    •          (One way due to ARP)
  39. What does velocity depend on?
    Where do AP occur?
    • Fiber Diameter
    • &
    • Myelination:Unmylinated: Slower
    • Mylinated: Faster

    AP occurs only at the axon/nodes of ranvier
  40. Diferences between
    Graded Potential and Action Potential
    • Graded.P                                  Action .P
    • -Amplitude varies w/size         -All or None
    • -Can b Summed             -Cannot B Summed
    • -No refactory period    -Has Refactory Period
    • -Dec w/dist    -Constant value deploarization
    • -Duration varies        -Duration is constant   
    • w/initiating cond
    • -Depolari/Hyperpolari    -Depolarization only
    • -Initiated by receptor,    -Initiated by G.P
    • neurotr(synapse), or spontaneously.
    • Mechan. depends on -Depend Voltage-gated
    • Ligand-gated chans
  41. What is resting membrane potential usually at?
    -70mV
  42. When does Hyperpolarization occur?
    • When below resting membrane potential.
    • (below -70    ex: -80)
  43. If threshold is higher than -70mV in AP does that mean the peak will be higher as well?
    • No!
    • Peek is usually at around +60 mV and thats when inactivation gates close, K+ voltage gates open, and depolarization occurs.
  44. Can another action potential occur in the midst of one occuring?
    • NO!
    • Only during the Absolute Refactory Period few mili seconds.

    This is due to Na+ Gates that are closed & inactivation gates are not yet reset.

    Assures one way travel of AP by preventing backward conduction.
  45. Define Synapses
    WHat are the two kinds?
    Specialized junctions between neurons where electrical activity of the presynaptic neuron influences postsynaptic neuron

    • Two Kinds:
    • Chemical - Most common type
    • Electrical - Called electrotonic
  46. Receptors have two parts:
    • Binding component - Binds 2 neurotransmitter.
    • Ionophore component - Is inside &opens chans
  47. Anatomy of synapse
    • Presynaptic neuron->
    • Synaptic Cleft ->
    • Postsynaptic Neuron ->


    Presynaptic neuron releases neurotransmitters which diffuse across synaptic cleft and attach to specific receptors in the post-synaptic membrane.
  48. Metabotropic Receptor
    • Allow for fast or inhibatory transportation in nervous system.
    • Can take neuron away from threshold (hyperpolorization)
    • Or take post synaptic neuron towards towards threshold
    • (Depolarization)

    • Neurotransmitter binds to metabotropic
    • results in release of G-protein from receptor
  49. Ionotropic:
    • Post synaptic receptor  on phospho lipid bilaye
    • Neurotransmitter binds to Ionotropic receptor causing an openning of ion channel
    • CHanges shape and allows Sodium ions in.

    quickly depolarizes or hyperpolarizes post synaptic neuron.
  50. Types of terminal end knobs
    • Discrete synapses: One area of contact
    • Diffuse: Several areas of contact
  51. Synapses can be:
    • Excitatory: produce brief action potential to +
    • or
    • Inhibatory:produce brief action potential to -
  52. Functional Aspect of synapses:
    How signal is transmitted neuron to neuron in ACH synapse.
    Depolarization in pre-synaptic neuron causes opening of voltage-sensitive Ca2+ channels.

    • Ca diffuses into terminal end knob -> -Calmodulin Activated
    • -Protein Kinase
    • -phosphorylates synapsins or SNARE -proteins which stimulate vessicles to attach to attachment sites or docking proteins
    • -release contents into cleft = Exocytosis
    • -Neurotr. diffuse across cleft/bind to proteins in post synaptic density neuron.
    • -Achesterase: enzyme that brks down ACH
    • -receptors open receptor-operated chan to allow in Na+
  53. Postsynaptic ACH receptors may be....
    • Nicotinic
    • Muscularinic
  54. What are the five major groups neurotransmitters can be divided into?
    • Low Molecular Weight Neurotransmitter
    • Biogenic Amines or Momoamines
    • Amino Acid Transmitters
    • Neuropeptides (Large molecules)
    • Nitric Oxide Neurotransmitters
  55. Iontropic vs Metbroactive
  56. Ionotropic receptors form an ion channel pore.
    Metabotropic: G-Protein coupled receptor

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