Reticular formation Flashcards
RF in diencephlaon
Intralaminar nuclei: centromedian nucleus, midline nuclei, reticular nucleus
RF in midbrain and functions
Periaqueductal gray
Pain and pee
RF in pons
Raphe nucleus
Locus ceruleus (norE): rostral pons near 4th ventricle
Paramedian pontine RF: horizontal conjugate eye movement
RF responsible for sending fibers to cerebral cortex to signal consciouness
Pontomesencephalic reticular formation -> Central tegmentum tract -> intralaminar nuclei +basal forebrain -> RAS
The pontomesencephalic reticular formation (in the region of the rostral reticular formation) forms a circuit together with intralaminar nuclei of the thalamus that is critical to maintaining normal consciousness. The Intralaminar nuclei in turn project to the cerebral cortex.
Lateral reticulospinal tract receives fibers from __
Medullary reticular formation
What is the role of RF in sleep?
Lateral reticulospinal tracts cause muscle tone loss during REM sleep by inhibiting the firing of motor neurons.
Why does being in pain keep us awake?
Spinoreticular tract responsible for pain sends signals to RAS.
RF is responsible for __
Pain modulation
RF motor functions
Cycle: CPG e.g. walking and running
RF nuclei involved with respiration
Pontine respiratory center PRG in pons
VRG, DRG in medulla
Where does RF nuclei receive information for respiratory modulation?
Solitary nuc. sends signals to these respiratory centers.
RF nuclei involved with cardiovascular fxns
VentroLateral Medulla (VLM) controls HR, BP
Afferent fibers to the VLM center are __
Baroreceptors CN IX, X sends info to solitary nuc. and then to VLM
How is our circadian rhythm established?
Suprachiasmatic nucleus –> Hypothalamus –> Pontomesencephalic reticular formation
The pontomesencephalic reticular formation (in the region of the rostral reticular formation) forms a circuit together with intralaminar nuclei of the thalamus that is critical to maintaining normal consciousness. The Intralaminar nuclei in turn project to the cerebral cortex.
What is the basal forebrain?
The basal forebrain structures are located in the forebrain to the front of and below the striatum. They include the ventral basal ganglia (including nucleus accumbens and ventral pallidum), nucleus basalis, diagonal band of Broca, substantia innominata, and the medial septal nucleus.
What is the nucleus basalis of Meynert?
The nucleus basalis, also known as the nucleus basalis of Meynert or nucleus basalis magnocellularis, is a group of neurons located mainly in the substantia innominata of the basal forebrain.
Noradrenergic system
Mainly in locus ceruleus near 4th ventricle in rostral pons. Activity increases when awake and lessens when sleeping.
Histaminergic system
Mainly in tuberomamillary nucleus of posterior hypothalamus. Maintains alert state (nonselective histamines can cause drowsiness).
Cholinergic system
Mainly in basal forebrain and RF in midbrain-pons (pedunculopontine nuc.). Arousal effect.
Serotonergic system
Located in raphe nuclei at all levels of brainstem.
How is sleep initiated?
Preoptic area in ant. Hypothalamus contains NREM-on cells that inhibit histaminergic neurons in tuberomamillary nuc. in post. Hypothalamus.
How is REM sleep initiated?
REM-on cells in pontine RF (Cholinergic) alternatively turn on with REM-off cells in Locus ceruleus and raphe nuclei.
During REM, REM-on cells send signals down ventral medial medulla to inhibit LMN. They also cause waking-like EEG and motor movement of eyes.
What simulates NREM-on cells?
Suprachiasmatic nucleus
NREM-on cells fxn
Inhibit orexin neurons (perifornical area of hypothalamus) that normally activate histaminergic, cholinergic neurons
Absence of orexin or hypocretin causes …
Narcolepsy: sudden-onset of REM sleep
Cataplexy
Sudden loss of muscle tone during strong emotions e.g. positive ones
Sleep walking during __ phase of sleep
NREM
Acting out dreams occurs in __ phase of sleep
REM.
More common in geriatric patients due to deterioration of ventral medial medulla or lateral reticulospinal tract.
Glasgow scale
Coma scale measures
1. Eye opening
2. Verbal response
3. Motor response
Raphe nucei
The raphe nucleus is considered to be part of the reticular formation and is located in the brainstem. It is responsible for the release of serotonin to other parts of the brain.
medial zone of RF fxn
Major source of long ascending and descending projections
