RETICULAR FORMATION RETICULAR FORMATION AND AROUSAL/SLEEPAND AROUSAL/SLEEP

71 湯燕傑79 廖于樟

Structure of RFStructure of RF

RETICULAR FORMATION –AFFERENT & RETICULAR FORMATION –AFFERENT & EFFERENT CONNECTIONS OF RETICULAR EFFERENT CONNECTIONS OF RETICULAR FORMATIONFORMATION

Reticular Formation

Reticular Formation

Cerebellum

Red Nucleus

Thalamus, Hypothalamus

SC

CortexSubstancia Nigra

Tectum

EFFERENT CONNECTION TO EFFERENT CONNECTION TO THE RETICULAR FORMATIONTHE RETICULAR FORMATION

AFFERENT CONNECTION TO AFFERENT CONNECTION TO THE RETICULAR FORMATIONTHE RETICULAR FORMATION

Cortex

Thalamus

Corpus Striatum

Cerebellum

SC

Sensory Pathways

(Touch, pain, temperature, kinesthestic sensation)

Optic, auditory olfactory and taste pathways

Sleep CentresSleep Centresactually generate sleepactually generate sleep

hypothalamus(ant: awakening, post:sleep)

reticular formation area below midpons(cholinergic,

serotoninergic ->sleepadrenergic ->

wakefulness) sleep generating

substances in CSF after long sleep deprivation

Reticular activating Reticular activating systemsystem The reticular activating system (RAS) is

an area of the brain responsible for regulating arousal and sleep-wake transitions.

Regulating Sleep-Wake Transitions – electrical activity

The relationship between RAS and sleep-wake

Attention

BRAIN WAVES AND BRAIN WAVES AND AROUSAL/SLEEPAROUSAL/SLEEP

Awake Awake Slow-wave sleepSlow-wave sleep REMREM Deep sleepDeep sleep

REGULATION OF SLEEPREGULATION OF SLEEP

Stimulation of certain specific areas of the brain can produce sleep with characteristics near those of natural sleep, such as:

The raphe nuclei in the lower half raphe nuclei in the lower half of the pons & in the medullaof the pons & in the medulla;

The nucleus of the tractus nucleus of the tractus solitariussolitarius;

Several regions of the diencephalondiencephalon, such as rostral portion of the rostral portion of the hypothalamushypothalamus ( mainly in the suprachiasmal area) & an occasial area in the diffuse nuclei of the diffuse nuclei of the thalamusthalamus.

Which send fibers to the brain stem reticular formation & also

to the hypothalamus, thalamus, most of the areas of

the limbic system, to the neocortex & also to the SC;

Many nerve endings from these fibers produce SEROTONINSEROTONIN,

that if blocked doesn’t allow the production of sleep for several

days.

REGULATION OF SLEEPREGULATION OF SLEEP

Lesions in the raphe nuclei lead to high state of wakefulness;

Bilateral lesions in the medial rostral suprachiasmal area in the anterior hypothalamus also cause wakefulness;

In both cases, the excitatory reticular nuclei of the mesencephalon and upper pons become released from inhibition, thus causing INTENSE INTENSE

WAKEFULNESSWAKEFULNESS

These type of lesions can lead to death of the animal due to exhaustionexhaustion.

REGULATION OF SLEEPREGULATION OF SLEEP

There are also other possible transmitter substances related to sleep

in the CSF, in blood or urine of animals kept awake over a long period,there are substances that cause sleep when injected into the brain ventricular

system of another animal.

• MURAMYL PEPTIDE in CSF;

• Another nonpeptide isolated from blood of sleeping animals;

• Another unidentified substance found in the neuronal brain stem of animals, causes the accumulation of sleep factors ( in CSF or in the brain stem) leading to sleep.

CYCLE BETWEEN SLEEP & CYCLE BETWEEN SLEEP & WAKEFULNESSWAKEFULNESS

There’s yet no explanation for the reciprocal operation of the sleep-wakefulness cycle;

But some suggest that when the sleep centers are NOT activatedsleep centers are NOT activated, the mesencephalic & upper pontile RAS are released from mesencephalic & upper pontile RAS are released from inhibitioninhibition, which allows the , which allows the RAS to become spontaneously activeRAS to become spontaneously active;

This will excite PNS & excite PNS & CCerebral erebral CCortexortex, both of which send POSITIVE FEEDBACK to the same reticular activating nuclei to activate them still further;

So, once wakefulness starts it has a natural tendency to sustain itself;

After a few hours, the brain & even neurons themselves become fatigued & the positive feedback fades & sleep- promoting centers take over.

OtherOther FunctionFunction Somatic motor control Cardiovascular control Pain modulation - The reticular formation

is one means by which pain signals from the lower body reach the cerebral cortex.

Sleep and consciousness Habituation Dream

Reference http://bhavanajagat.files.wordpress.com/2011/02/reticular-f

ormation.jpg http://www.becomehealthynow.com/images/organs/nervou

s/brain_stem1.jpg http://www.ncbi.nlm.nih.gov/bookshelf/picrender.fcgi?

book=neurosci&part=A1157&blobname=ch17f3.jpg http://blog.yam.com/itoyukiya/article/28350226 http://en.wikipedia.org/wiki/Reticular_activating_system http://en.wikipedia.org/wiki/Reticular_formation http://www.semel.ucla.edu/sleepresearch/

sleepDream/sleep_dreams.htm http://physiology.lf2.cuni.cz/