Pathophysiology

Cards (16)

  • Give 5 dopaminergic pathways.
    Direct
    Indirect
    Hyperdirect
    Mesolimbic
    Mesocortical
  • Describe the direct basal ganglia pathway.
    FUNCTION: Reinforces cortical activity
    Cortex sends excitatory impulse to striatum -> striatum sends inhibitory impulses to globus pallidus interna -> less inhibitory signals sent from GPI to thalamus -> more excitatory impulses from thalamus to cortex
  • What is the effect of the substantia nigra pars compacta on the direct pathway?
    Promotes direct pathway
    Activation of dopaminergic neuronsdopamine released into striatumdopamine binds to D1 receptors in striatumactivation of striatumpromotion of direct (’go’) pathway
  • What is the function of the indirect basal ganglia pathway?
    Inhibits cortical activity of neighbouring areas of cortex
  • Indirect basal ganglia pathway (w/o subthalamic nucleus)
    Cortex sends excitatory impulses to the striatum -> striatum sends inhibitory impulses to the globus pallidus externa -> GPE in inhibited from sending its inhibitory impulses to GPI -> so GPI sends more inhibitory signals to the thalamus -> thalamus is inhibited, so doesn’t send excitatory signals to the cortex
  • Indirect basal ganglia pathway (w/subthalamic nucleus).
    Cortex sends excitatory impulses to the striatum -> striatum sends inhibitory impulses to the globus pallidus externa -> GPE is inhibited from sending inhibitory impulses to subthalamic nucleus -> subthalamic nucleus sends excitatory impulses to globus pallidus interna -> GPI sends inhibitory impulses to thalamus -> thalamus is inhibited, so doesn’t send excitatory signals to the cortex
  • What is the effect of the substantia nigra on the indirect pathway?
    Substantia nigra pars compacta -> activation of dopaminergic neuronsdopamine released into striatumdopamine binds to D2 receptors in striatuminhibition of striatuminhibition of indirect (’stop’) pathway
  • What is the function of the hyperdirect basal ganglia pathway?
    Thought to prevent unwanted movement in advance
  • Hyperdirect basal ganglia pathway.
    Cortex sends excitatory impulses to the subthalamic nucleus -> subthalamic nucleus sends excitatory signals to globus pallidus interna -> GPI sends inhibitory impulses to thalamus -> thalamus is inhibited, so doesn’t send excitatory signals to the cortex
  • Mesolimbic pathway.
    Exposed to rewarding stimulusincreased release of dopamine from ventral tegmental area (VTA) → activation of dopaminergic neurons in VTA → neurons project to nucleus accumbens (via mesolimbic pathway) → dopamine levels in nucleus accumbens increase
  • Mesocortical pathway.
    Exposed to rewarding stimulus → increased release of dopamine from VTAactivation of dopaminergic neurons in VTA → neurons project to cortex (esp. frontal lobes) → dopamine levels in cortex increases
    Considered part of the reward system
  • Pathophys of PD.
    Alpha-synuclein aggregates & tangles → creation of Lewy body inclusionsneuronal cell death (esp. dopaminergic neurons in substantia nigra pars compacta) → decrease in dopamine & increase in AChless dopamine released at striatum via nigrostriatal pathwaysless direct pathway & more indirect pathwaydegeneration spreads as the condition progresses → spreads from lower brainstem to midbrain, then to cortex
    When someone loses around 80% of dopaminergic neuronsmotor symptoms appear
  • Pathophys of Huntington's
    Mutations in Huntington gene → CAG repeat sequence (encodes for glutamine) → misfolded Huntington protein (more than 40 CAG repeats) → protein aggregation & neuronal cell death in striatumloss of indirect circuits → shift in direct vs indirect balance towards direct pathway → hyperkinesia (loss of inhibition)
  • Fill in the blanks
    A) Indirect
    B) Cortex
    C) Striatum
    D) GPe
    E) Subthalamic nucleus
    F) GPi
    G) Thalamus
  • Fill in the blanks
    A) Indirect
    B) Cortex
    C) Striatum
    D) GPe
    E) Subthalamic nucleus
    F) GPi
    G) Thalamus
    H) Substantia nigra
    I) D2
  • Fill in the blanks
    A) Direct
    B) Cortex
    C) Striatum
    D) GPi
    E) Thalamus
    F) Substantia nigra
    G) D1