SLEEP centres in brain

1 RAS

(reticular activating system) is a set of connected nuclei responsible for regulating wakefulness and sleep wake transitions. RAS has both cholinergic and adrenergic components.
Anatomical components of RAS are

  • Mid-brain reticular formation,
  • Dorsal hypo-thalamus,
  • Thalamic intra laminar nuclei,
  • Tegmentum.

CHOLINERGIC:

  1. Neuro-transmitters having quaternary ammonium salts,
  2. Present in acetylcholine and functions with inositol and basic constituent of lecithin,
  3. Prevents fat deposition in liver,
  4. Parasympathetic system communicates via cholinergic pathway.

ADRENERGIC:

  1. Working on adrenaline or nor-adrenaline,
  2. Adrenalic nervous system as part of autonomous system,
  3. No role in modulating activity of RAS neurons.

Reticular formation by

  1. Visual impulse,
  2. Ascending sensory tract,
  3. Auditory impulse ,
  4. Descending motor.

3.png

Fig1: Reticular formation

Reference:http://www.daviddarling.info/encyclopedia/R/reticular_formation.html

2.1 SLEEP CENTRES

2.1.1 Locus coeruleus
It secrets norepinephrine,
Area of action: Hypothalamus, thalamus, cerebellum.

2.1.2 Substantia nigra and ventral tegmental area
It secrets dopamine,
Area of action: Basal nuclei, prefrontal cortex.

2.1.3 Raphe nuclei
It secrets serotonin,
Area of action: Basal nuclei, cerebellum.

2.1.4 Pontine nuclei
It secrets acetyl-choline,
Area of action: Fornix, cingulate gyrus.

2.1.5 Medullary synchronization area
May stimulate the Raphe nuclei,
Area of action: nuc. tractus solitarius level.

2.1.6 Encephalic sleep areas
Area of action:
I. Rostral of hypothalamus, especially the supra-chiasmatic area,

II. Intra-laminar and anterior thalamic nuclei.

2.1.7 Basal forebrain sleep area
Area of action: Pre-optic area and Broca’s diagonal band.

3.png

Fig2:  Neuromodulator Systems

2.2 Major centers for sleep and factors interfering sleep

Location

Function

Thalamus Cortical activation

Sleep spindle

EEG synchronization

Hypo-thalamus Sleep/watch switch
SCN Circadian clock
Brain-stem Ascending cortical activation

REM/ SWS switch

Factor

Function
adenosine Inhibits cholinergic neurons of RAS which stimulate cortex
PgD2 (Prosta-glandin D2) Increase sleep tendency

Hypothalamus secrets it

PgE2 (Prosta-glandin E2) Secreted by hypothalamus
IL-1 Immunological role
Sleep inducing factor
Muramil peptide Cytokine activation

2.3 RETINO-HYPOTHALAMIC PATHWAY

The retino-hypothalamic tract (RHT) is a photic neural input pathway involved in the circadian rhythms of mammals. The origin of the retino-hypothalamic tract is the intrinsically photosensitive retinal ganglion cells (ipRGC), which contain the photo pigment melanopsin. The axons of the ipRGCs belonging to the retino-hypothalamic tract project directly, monosynaptically, to the supra-chiasmatic nuclei (SCN) via the optic nerve and the optic chiasm.

3.png

Fig3: Retino-hypothalamic tract

Reference: http://www.neurology.org

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About YANAMALA VIJAY RAJ

Mtech in Clinical Eng Jointly offered by Indian institute of technology Madras& Christian medical college Vellore& Sree chitra tirunal institute for medical sciences and technology Trivandrum.
This entry was posted in biomedical, Physiology and tagged , , , , , , , , , . Bookmark the permalink.

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