FORMACION RETICULAR PDF

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[{“id”,”question”:”FORMACIÓN RETICULAR”,”answer”:”1. Mediana\n2. Magnocelular\gnocelular\n4. Parvicelular\n”,”position” FORMACIÓN RETICULAR Organización General La formación reticular consiste en una red continua de células y fibras nerviosas asentada en zonasprofu. ¿Dónde se encuentra la formación reticular? a) Centro del Tronco encefálico b) Corteza cerebral c) Medula espinal d) Lóbulo temporal 2. La formación reticular.

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The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. The reticular formation is not anatomically well defined because it includes reticlar located in diverse parts of the brain. The neurons of the reticular formation make up a complex set of networks in the core of the brainstem that stretch from the upper part of the midbrain to the lower part of the medulla oblongata.

Neurons of the reticular formation, particularly those of the ascending reticular activating system, play a crucial role in maintaining behavioral arousal and consciousness. The functions of the reticular formation are modulatory and premotor.

Formación reticular

The modulatory functions are primarily found in the rostral sector of the reticular formation and the premotor functions are localized in the neurons in more caudal regions. The reticular formation is divided into three columns: The raphe nuclei are the place of synthesis of the neurotransmitter serotoninwhich fprmacion an important role in mood regulation.

The gigantocellular nuclei are involved in motor coordination. The parvocellular nuclei regulate exhalation. The reticular formation is essential for governing some of the basic functions of higher organisms and is one of the phylogenetically oldest portions of the brain.

The human reticular formation is composed of almost brain nuclei and contains many projections into the forebrainbrainstemand cerebellumamong other regions. The original functional differentiation was a division of caudal reticuular rostral. This was based upon the observation that the lesioning of the rostral reticular formation induces a hypersomnia in the cat brain.

In contrast, lesioning of the more caudal portion of the reticular formation produces insomnia in cats. This formaciin has led to the idea that the caudal portion inhibits the rostral portion of the reticular formation. Sagittal reticulra reveals more morphological distinctions. The raphe nuclei form a ridge in the middle of the reticular formation, and, directly to its periphery, there is a division called the medial reticular formation.

The medial RF is large and has long ascending and descending fibers, and is surrounded by the lateral reticular formation. The lateral RF is close to the motor nuclei of the cranial nerves, and mostly mediates their function. The medial reticular formation and lateral reticular formation are two columns of neuronal nuclei with ill-defined boundaries that send projections through the medulla and into the mesencephalon midbrain. The nuclei can be differentiated by function, formaion type, and projections of efferent or afferent nerves.

Moving caudally from the rostral midbrainat the site of the rostral pons and the midbrain, the medial RF becomes less prominent, and the lateral RF becomes more prominent.

Existing on the sides of the medial reticular formation is its lateral cousin, which is particularly pronounced in the rostral medulla and caudal pons. Out from this area spring the cranial nerves, including the very important vagus nerve. The Lateral RF is known for its ganglions and areas of interneurons around the cranial nerveswhich serve to mediate their characteristic reflexes and functions.

The reticular formation consists of more than small neural networks, with varied functions including the following:. The ascending reticular activating system ARASalso known as the extrathalamic control modulatory system or simply the reticular activating system RASis a set of connected nuclei in the brains of vertebrates that is responsible for regulating wakefulness and sleep-wake transitions.

Formación reticular | Flashcards

The ARAS is a part of the reticular formation and is mostly composed of various nuclei in the thalamus and a number of dopaminergicnoradrenergicserotonergichistaminergiccholinergicand glutamatergic brain nuclei.

The ARAS is composed of several neuronal circuits connecting the dorsal part of the posterior midbrain and anterior pons to the cerebral cortex via distinct pathways that project through the thalamus and hypothalamus. The neurotransmitters that geticular neurons release include formacionorepinephrineserotoninhistamineacetylcholineand glutamate.

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The thalamic pathway consists primarily of cholinergic neurons in the pontine tegmentumwhereas the hypothalamic pathway is composed primarily of neurons that release monoamine neurotransmittersnamely dopamine, norepinephrine, reticcular, and histamine. The ARAS consists of evolutionarily ancient areas of the brain, which are crucial to survival and protected during adverse periods. As a result, the ARAS still functions during inhibitory periods of hypnosis.

The ascending reticular activating system is an important enabling factor for the state of consciousness.

The main function of the ARAS is to modify and potentiate thalamic and cortical function such that electroencephalogram EEG desynchronization ensues. Low voltage fast burst brain waves EEG desynchronization are associated with wakefulness and REM sleep which are electrophysiologically similar ; high voltage slow waves are found during non-REM sleep. Generally speaking, when thalamic relay neurons are in burst mode the EEG is synchronized and when they are in tonic mode it is desynchronized.

The physiological change from a state of deep sleep to wakefulness is reversible and mediated by the ARAS.

Reticular formation

During sleep, neurons in the ARAS will have a much lower firing rate; conversely, they will have a higher activity level during the waking state. In order that the brain may sleep, there must be a reduction in ascending afferent activity reaching the cortex by suppression of the ARAS. The ARAS also helps mediate transitions from relaxed wakefulness to periods of high attention. Mass lesions in brainstem ARAS nuclei can cause severe alterations in level of consciousness e.

Direct electrical stimulation of the ARAS produces pain responses in cats and educes verbal reports of pain in humans. These results suggest some relationship between ARAS circuits and physiological pain pathways. Given the importance of the ARAS for modulating cortical changes, disorders of the ARAS should result in alterations of sleep-wake cycles and disturbances in arousal.

If coupling were down-regulated, there would be a corresponding decrease in higher-frequency synchronization gamma band. Conversely, up-regulated electrical coupling would increase synchronization of fast rhythms that could lead to increased arousal and REM sleep drive. There are several potential factors that may adversely influence the development of the ascending reticulr activating system:.

Formación reticular

The reticulospinal tractsalso known as the descending or anterior reticulospinal tracts, are extrapyramidal motor tracts that descend from the reticular formation [37] in two tracts reticukar act on the motor neurons supplying the trunk and proximal limb flexors and extensors.

The reticulospinal tracts are involved mainly in locomotion and postural control, although they do have other functions as well. The reticulospinal tracts works with the formacioh three pathways to give a coordinated control of movement, including delicate manipulations.

The medial system includes the reticulospinal rdticular and the vestibulospinal pathwayand this system provides control of posture. The corticospinal and the rubrospinal tract pathways belong to the retciular system which provides fine control of formmacion.

The ascending sensory tract conveying information in the opposite direction is known as the spinoreticular tract. The reticulospinal tracts are mostly inhibited by the corticospinal tract ; if damage occurs at the level of or below formavion red nucleus e. Allan Hobson states in his book The Reticular Formation Revisited that the name is an etymological vestige from the fallen era of the aggregate field theory in the neural sciences.

Foormacion term ” reticulum ” means “netlike structure”, which is what the reticular formation resembles rericular first glance.

It has been described as being either too complex to study or an undifferentiated part of the brain with no organization at all. Eric Kandel describes the reticular formation as being organized in a similar manner to the intermediate gray matter of the spinal cord. This chaotic, loose, and intricate form of organization is what has turned off many researchers from looking farther into this particular area of the brain.

The term “reticular formation” is seldom used anymore except to speak in generalities. Modern scientists usually refer to the individual nuclei that compose the reticular formation. Moruzzi and Magoun first investigated the neural components regulating the brain’s retivular mechanisms in Physiologists had proposed that some structure deep within the brain controlled mental wakefulness and alertness.

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The direct electrical stimulation of the brain could simulate electrocortical relays. Magoun used this principle to demonstrate, on two separate areas of the brainstem of a cat, how to produce wakefulness from sleep. First the ascending somatic and auditory retichlar second, a series of “ascending relays from the reticular formation of the lower brain stem through the midbrain tegmentumsubthalamus and hypothalamus to the internal capsule.

Next, the significance of this newly identified relay system was evaluated by placing lesions in the medial and lateral portions of the front of the midbrain. Cats with mesancephalic interruptions to the ARAS teticular into a deep sleep and displayed corresponding brain waves. In alternative fashion, cats with similarly placed interruptions to ascending auditory and somatic pathways exhibited normal sleeping and wakefulness, and could be awakened with somatic stimuli.

Because these external stimuli would be blocked by the interruptions, this indicated that the ascending transmission must travel through the newly discovered ARAS.

Finally, Magoun recorded potentials within the medial portion of the brain stem and discovered that auditory stimuli directly fired portions of the reticular activating system. Furthermore, single-shock stimulation of the sciatic nerve also activated the medial reticular formation, hypothalamusand thalamus.

Excitation of the ARAS did not depend on further signal propagation through the cerebellar circuits, as the same results formcion obtained following decerebellation and decortication.

The researchers proposed that a column of cells surrounding the midbrain reticular formation received input from all the ascending tracts of the brain forkacion and relayed these afferents to the cortex and therefore regulated wakefulness. From Wikipedia, the free encyclopedia. Reticular formation Axial section of the ponsat its upper part.

Formatio reticularis labeled at left. Section of the medulla oblongata at about the middle of the olive. Formatio reticularis grisea and formatio reticularis alba labeled at left. This section needs expansion with: You can help by adding to it.

rreticular This article uses anatomical terminology; for an overview, see anatomical terminology. The ascending reticular activating system ARAS is responsible for a sustained wakefulness state. It flrmacion information formavion sensory receptors of various modalities, transmitted through spinoreticular pathways and cranial nerves trigeminal nerve — polymodal pathways, olfactory nerve, optic nerve and vestibulocochlear nerve — monomodal pathways. These pathways reticulra the thalamus directly or indirectly via the medial column of reticular fomracion nuclei magnocellular nuclei and reticular nuclei of pontine tegmentum.

The reticular activating system begins in the dorsal part of the posterior midbrain and anterior pons, continues into the diencephalon, and then divides into two parts reaching the thalamus and hypothalamus, which then project into the cerebral cortex Fig.

The thalamic projection is dominated by cholinergic neurons originating from the pedunculopontine tegmental nucleus of pons and midbrain PPT and laterodorsal tegmental nucleus of pons and midbrain LDT nuclei [17, 18]. The hypothalamic projection involves firmacion neurons of the locus coeruleus LC and serotoninergic neurons of the dorsal and median raphe nuclei DRwhich pass through the lateral hypothalamus and reach axons of the histaminergic tubero-mamillary nucleus TMNtogether forming a pathway extending into the forebrain, cortex and hippocampus.

Cortical arousal also takes advantage of dopaminergic neurons of the substantia nigra SNventral tegmenti area VTA and the periaqueductal grey area PAG. Fewer cholinergic neurons of the pons and midbrain send projections to the forebrain along the ventral pathway, bypassing the thalamus [19, 20]. Human Neuroanatomy 2nd ed.

Archived from the original on 4 May Retrieved 4 September Archived from the original on Annals of the New York Academy of Sciences. A Foundation for Clinical Neuroscience 2nd ed. The RAS is a complex structure consisting of several different circuits including the four monoaminergic pathways