Neuroanatomy Draw It To Know It

440 Neuroanatomy: Draw It to Know It

Know-It Points

Sleep Neurocircuitry ( Advanced )

■ Th e area for non-REM sleep induction lies within the
anterior hypothalamus, specifi cally in the ventrolateral
preoptic area and the median preoptic nucleus.
■ Th e thalamocortical networks generate sleep
electroencephalographic (EEG) patterns: sleep
spindles and slow-wave sleep.
■ Th e reticular thalamic nuclei gate the fl ow of
information between the thalamus and cortex.
■ When the thalamocortical membrane hyperpolarizes
more negatively than –65 mV, T-type calcium
channels open, which generates a low-threshold spike.

■ Th rough the phenomenon of sensory gating , sensory

stimuli that might otherwise wake us from sleep fail

to reach our cerebral cortex.

■ Th e putative primary REM-promoting region lies

within the pons in what is called the sublaterodorsal

nucleus in the rat and the peri-locus coeruleus in the

cat.

■ Th e supra-olivary medulla is responsible for muscle

atonia during REM sleep.

Suprachiasmatic Circuitry

■ Our internal clock allows us to maintain a 24-hour
cycle of behavioral activities even when we are placed
in non-24-hour environments.
■ Th e timing of our internal clock is aff ected by certain
environmental cues, called zeitgebers, of which light
is commonly considered the most potent.
■ Th e retinohypothalamic pathway:

• Dark phase:
   Descending hypothalamospinal projections from
  the paraventricular nucleus excite the cervical
  spinal cord

 Th e cervical spinal cord excites the superior

cervical ganglion

 Th e superior cervical ganglion activates the

production of melatonin in the pineal body

• Light phase:
   Th e suprachiasmatic nucleus inhibits the
  paraventricular nucleus, thus inactivating the rest
  of the pathway
  ■ Tumor necrosis factor-alpha and interleukin-1 are
  two well-studied substances with sleep-promoting
  p r o p e r t i e s.

Wakefulness Circuitry

■ Th e laterodorsal tegmental and pedunculopontine
nuclei lie within the lower midbrain and upper pons
and are cholinergic.
■ Th e locus coeruleus lies, most notably, within the
posterior pons and is noradrenergic.
■ Th e substantia nigra and ventral tegmental area lie
within the anterior midbrain and are dopaminergic.
■ Th e dorsal group of raphe nuclei lie within the
central upper pons and midbrain and are serotinergic.

■ Th e tuberomammillary nucleus lies within the

hypothalamus and is the sole source of histamine in

the brain.

■ Cholinergic basal forebrain nuclei lie within the

ventral surface of the frontal lobe.

■ Th e intralaminar thalamic nuclei play an important

role in the ascending arousal system.