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Nervous System: Unit IV > Cerebral Cortex > Flashcards

Flashcards in Cerebral Cortex Deck (5)
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1

Major divisions of the cerebral cortex

  • neocortex ("isocortex") vs. allocortex ("other" cortex)
    • neocortex = 6-layered cortex
      • most extensive
      • variations of cell size/density btwn layers ==> broadmann's subdivisions
  • granular vs. agranular cortex
    • agranular cortex = motor + premotor cortex (BA 4 and 6)
      • granule cells = poorly developed
      • pyramidal layers = prominent
      • fxn = output
    • granular cortex
      • cell layers receive inputs
      • fxn = sensory/afferent

2

Characteristics of layers of neocortex

  • Ascending pathway
    • target of the ascending pathway = layer 4
    • layer 4 relay signals to layers 3 and 2
  • Descending pathway
    • layer 1 = target of descending
      • almost devoid of cell bodies
      • incoming axonal ramifications + branching apical dendrites + glial
    • inputs to layer 5 from layer 2/3

3

EEG measurements

  • electrical potential fluctuations at scalp surface
  • temporal and spatial summation of 
    electrical currents caused by the relatively slow postsynaptic potentials induced in neruons of cerebral cortex
  • Frequencies and patterns relate roughly to different states of being (Relaxed/Alert/Drowsy/REM/Dreamless)
    • higher frequecies = more activity
    • lower frequencies = less activity

4

Classification of EEG rhythms

  • Αlpha rhythms are in sensory cortices when you aren’t doing very much
  • Beta rhythms = alert, REM sleep
  • δ: below 3.5Hz
  • Θ : 4-7.5 Hz
  • α 8-13 Hz
  • β: 14-30 Hz
  • ɣ: 30-100 Hz

5

Rhythmic vs. Random discharge of thalamic neurons 

  • Rhythmic
    • e.g. reticular nucleus 
    • T-type channels ==> rhythmic firing during:
      • slow-wave sleep
      • deep anesthesia
      • absence seizures
    • represents temporary detachment of thalamic relay cells from sensory inputs
  • Random
    • ACh depolarizes relay neurons & inhibits reticular nucleus
    • ACh "opens" thalamocortical gate to sensory info ==> attention and arousal