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Mid Brain Activation

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About Midbrain –http://midbrain-activation.info/midbrain.html
midbrain

The midbrain is the smallest region of the brain that acts as a sort of relay station for auditory and visual information. The midbrain controls many important functions such as the visual and auditory systems as well as eye movement. Portions of the midbrain called the red nucleus and the substantia nigra are involved in the control of body movement.
The midbrain is located between the two developmental regions of the brain know as the forebrain and hindbrain.Within the midbrain is the reticular formation,Which is part of the tegmentum,a region of the brainstem that influences main functions.These two strutures,in addition to the globus pallidus,from the striatum.By inhibiting the action of neurons in the caudate nucleus and the putamen, the dopaminergic cell of the pars compacta influence the neuronal output of the neurotransmitter GABA (gamma-aminobutyric acid).The neurons in turn project to the cell of the pars reticulata,which,by projecting fibres to the thalamus,are part of the output system of the corpus striatum.
The interbrain also called as midbrain, located at the centre of the cerebrum, links and consolidates the functions of each part of the brain. It also allows the work of each file of the brain to appear onto consciousness.The interbrain acts as a sort of control tower of consciousness and is equipped with highly advanced intelligence.If a person develops his interbrain, he will acquire a memory that will allow him to never forget whatever he has seen or heard once.

Midbrain – All about Midbrain

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Mid Brain Activation

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About Midbrain
midbrain-http://midbrain-activation.info

The midbrain is the smallest region of the brain that acts as a sort of relay station for auditory and visual information. The midbrain controls many important functions such as the visual and auditory systems as well as eye movement. Portions of the midbrain called the red nucleus and the substantia nigra are involved in the control of body movement.
The midbrain is located between the two developmental regions of the brain know as the forebrain and hindbrain.Within the midbrain is the reticular formation,Which is part of the tegmentum,a region of the brainstem that influences main functions.These two strutures,in addition to the globus pallidus,from the striatum.By inhibiting the action of neurons in the caudate nucleus and the putamen, the dopaminergic cell of the pars compacta influence the neuronal output of the neurotransmitter GABA (gamma-aminobutyric acid).The neurons in turn project to the cell of the pars reticulata,which,by projecting fibres to the thalamus,are part of the output system of the corpus striatum.
The interbrain also called as midbrain, located at the centre of the cerebrum, links and consolidates the functions of each part of the brain. It also allows the work of each file of the brain to appear onto consciousness.The interbrain acts as a sort of control tower of consciousness and is equipped with highly advanced intelligence.If a person develops his interbrain, he will acquire a memory that will allow him to never forget whatever he has seen or heard once.

 

vishal bedi

Mid Brain Activation

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About Midbrain midbrain-activation.info
midbrain

The midbrain is the smallest region of the brain that acts as a sort of relay station for auditory and visual information. The midbrain controls many important functions such as the visual and auditory systems as well as eye movement. Portions of the midbrain called the red nucleus and the substantia nigra are involved in the control of body movement.
The midbrain is located between the two developmental regions of the brain know as the forebrain and hindbrain.Within the midbrain is the reticular formation,Which is part of the tegmentum,a region of the brainstem that influences main functions.These two strutures,in addition to the globus pallidus,from the striatum.By inhibiting the action of neurons in the caudate nucleus and the putamen, the dopaminergic cell of the pars compacta influence the neuronal output of the neurotransmitter GABA (gamma-aminobutyric acid).The neurons in turn project to the cell of the pars reticulata,which,by projecting fibres to the thalamus,are part of the output system of the corpus striatum.
The interbrain also called as midbrain, located at the centre of the cerebrum, links and consolidates the functions of each part of the brain. It also allows the work of each file of the brain to appear onto consciousness. The interbrain acts as a sort of control tower of consciousness and is equipped with highly advanced intelligence. If a person develops his interbrain, he will acquire a memory that will allow him to never forget whatever he has seen or heard once.

Антон Панов

Физиология

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Схема. Организация ретикулярной формации.

http://www.tryphonov.ru/tryphonov2/terms2/retcfr.htm

p.29 FIGURE 42A RETICULAR FORMATION 1 RETICULAR FORMATION: ORGANIZATION The reticular formation, RF, is the name for a group of neurons found throughout the brainstem. Using the ventral view of the brainstem, the reticular formation occupies the central portion or core area of the brainstem from midbrain to medulla (see also brainstem cross-sections in Figure 65–Figure 67).

 

This collection of neurons is a phylogenetically old set of neurons that functions like a network or reticulum, from which it derives its name. The RF receives afferents from most of the sensory systems (see next illustration) and projects to virtually all parts of the nervous system. Functionally, it is possible to localize different subgroups within the reticular formation:

  • Cardiac and respiratory “centers”: Subsets of neurons within the medullary reticular formation and also in the pontine region are responsible for the control of the vital functions of heart rate and respiration. The importance of this knowledge was discussed in reference to the clinical emergency, tonsillar herniation (with Figure 9B).
  • Motor areas: Both the pontine and medullary nuclei of the reticular formation contribute to motor control via the cortico-reticulo-spinal system (discussed in Section B, Part III, Introduction; also with Figure 49A and Figure 49B). In addition, these nuclei exert a very significant influence on muscle tone, which is very important clinically (discussed with Figure 49B).
  • Ascending projection system: Fibers from the reticular formation ascend to the thalamus and project to various nonspecific thalamic nuclei. From these nuclei, there is a diffuse distribution of connections to all parts of the cerebral cortex. This whole system is concerned with consciousness and is known as the ascending reticular activating system (ARAS).
  • Pre-cerebellar nuclei: There are numerous nuclei in the brainstem that are located within the boundaries of the reticular formation that project to the cerebellum. These are not always included in discussions of the reticular formation. It is also possible to describe the reticular formation topographically. The neurons appear to be arranged in three longitudinal sets; these are shown in the left-hand side of this illustration:
  • The lateral group consists of neurons that are small in size. These are the neurons that receive the various inputs to the reticular formation, including those from the anterolateral system (pain and temperature, see Figure 34), the trigeminal pathway (see Figure 35), as well as auditory and visual input.
  • The next group is the medial group. These neurons are larger in size and project their axons upward and downward. The ascending projection from the midbrain area is particularly involved with the consciousness system. Nuclei within this group, notably the nucleus gigantocellularis of the medulla, and the pontine reticular nuclei, caudal (lower) and oral (upper) portions, give origin to the two reticulo-spinal tracts (discussed with the next illustration, also Figure 49A and Figure 49B). • Another set of neurons occupy the midline region of the brainstem, the raphe nuclei, which use the catecholamine serotonin for neurotransmission.

 

The best-known nucleus of this group is the nucleus raphe magnus, which plays an important role in the descending pain modulation system (to be discussed with Figure 43). In addition, both the locus ceruleus (shown in the upper pons) and the periaqueductal gray (located in the midbrain, see next illustration and also Figure 65 and Figure 65A) are considered part of the reticular formation (discussed with the next illustration).

 

In summary, the reticular formation is connected with almost all parts of the CNS. Although it has a generalized influence within the CNS, it also contains subsystems that are directly involved in specific functions. The most clinically significant aspects are:

  • Cardiac and respiratory centers in the medulla
  • Descending systems in the pons and medulla that participate in motor control and influence muscle tone
  • Ascending pathways in the upper pons and midbrain that contribute to the consciousness system

    Схема. Ядра ретикулярной формации.
    Модификация: Hendelman W. Atlas of Funtional Neuroanatomy, Second Edition, 2006, 15,5 MB. Доступ к данному источнику = Access to the reference.

    p 31
    FIGURE 42B
    RETICULAR FORMATION 2
    RETICULAR FORMATION: NUCLEI In this diagram, the reticular formation is being viewed from the dorsal (posterior) perspective (see Figure 10 and Figure 40). Various nuclei of the reticular formation, RF, which have a significant (known) functional role, are depicted, as well as the descending tracts emanating from some of these nuclei. Functionally, there are afferent and efferent nuclei in the reticular formation and groups of neurons that are distinct because of the catecholamine neurotransmitter used, either serotonin or noradrenaline.

 

The afferent and efferent nuclei of the RF include: • Neurons that receive the various inputs to the RF are found in the lateral group (as discussed with the previous illustration). In this diagram, these neurons are shown receiving collaterals (or terminal branches) from the ascending anterolateral system, carrying pain and temperature (see Figure 34; also Figure 35). • The neurons of the medial group are larger in size, and these are the output neurons of the reticular formation, at various levels. These cells project their axons upward or downward. The nucleus gigantocellularis of the medulla, and the pontine reticular nuclei, caudal, and oral portions, give rise to the descending tracts that emanate from these nuclei — the medial and lateral reticulo-spinal pathways, part of the indirect voluntary and nonvoluntary motor system (see Figure 49A and Figure 49B). • Raphe nuclei use the neurotransmitter serotonin and project to all parts of the CNS.

 

Recent studies indicate that serotonin plays a significant role in emotional equilibrium, as well as in the regulation of sleep. One special nucleus of this group, the nucleus raphe magnus, located in the upper part of the medulla, plays a special role in the descending pain modulation pathway (described with the next illustration). There are other nuclei in the brainstem that appear to functionally belong to the reticular formation yet are not located within the core region.

 

These include the periaqueductal gray and the locus ceruleus. The periaqueductal gray of the midbrain (for its location see Figure 65 and Figure 65A) includes neurons that are found around the aqueduct of the midbrain (see also Figure 20B). This area also receives input (illustrated but not labeled in this diagram) from the ascending sensory systems conveying pain and temperature, the anterolateral pathway; the same occurs with the trigeminal system.

 

This area is part of a descending pathway to the spinal cord, which is concerned with pain modulation (as shown in the next illustration). The locus ceruleus is a small nucleus in the upper pontine region (see Figure 66 and Figure 66A). In some species (including humans), the neurons of this nucleus accumulate a pigment that can be seen when the brain is sectioned (prior to histological processing, see photograph of the pons, Figure 66). Output from this small nucleus is distributed widely throughout the brain to virtually every part of the CNS, including all cortical areas, subcortical structures, the brainstem and cerebellum, and the spinal cord.

 

The neurotransmitter that is used by these neurons is noradrenaline and its electrophysiological effects at various synapses are still not clearly known. Although the functional role of this nucleus is still not completely understood, the locus ceruleus has been thought to act like an “alarm system” in the brain. It has been implicated in a wide variety of CNS activities, such as mood, the reaction to stress, and various autonomic activities.

 

The cerebral cortex sends fibers to the RF nuclei, including the periaqueductal gray, forming part of the cortico-bulbar system of fibers (see Figure 46). The nuclei that receive this input and then give off the pathways to the spinal cord form part of an indirect voluntary motor system — the cortico-reticulo-spinal pathways (discussed in Section B, Part III, Introduction; see Figure 49A and Figure 49B). In addition, this system is known to play an extremely important role in the control of muscle tone (discussed with Figure 49B). CLINICAL ASPECT Lesions of the cortical input to the reticular formation in particular have a very significant impact on muscle tone. In humans, the end result is a state of increased muscle tone, called spasticity, accompanied by hyper-reflexia, an increase in the responsiveness of the deep tendon reflexes (discussed with Figure 49B).

© 2006
Схема. Ретикулярная формация. Система модуляции боли.
Модификация: Hendelman W. Atlas of Funtional Neuroanatomy, Second Edition, 2006, 15,5 MB. Доступ к данному источнику = Access to the reference.

FIGURE 43 RETICULAR FORMATION 3 PAIN MODULATION SYSTEM Pain, both physical and psychic, is recognized by the nervous system at multiple levels. Localization of pain, knowing which parts of the limbs and body wall are involved, requires the cortex of the postcentral gyrus (SI); SII is also likely involved in the perception of pain (discussed with Figure 36). There is good evidence that some “conscious” perception of pain occurs at the thalamic level. We have a built-in system for dampening the influences of pain from the spinal cord level — the descending pain modulation pathway.

 

This system apparently functions in the following way: The neurons of the periaqueductal gray can be activated in a number of ways. It is known that many ascending fibers from the anterolateral system and trigeminal system activate neurons in this area (only the anterolateral fibers are being shown in this illustration), either as collaterals or direct endings of these fibers in the midbrain. This area is also known to be rich in opiate receptors, and it seems that neurons of this region can be activated by circulating endorphins. Experimentally, one can activate these neurons by direct stimulation or by a local injection of morphine.

 

In addition, descending cortical fibers (cortico-bulbar) may activate these neurons (see Figure 46). The axons of some of the neurons of the periaqueductal gray descend and terminate in one of the serotonincontaining raphe nuclei in the upper medulla, the nucleus raphe magnus. From here, there is a descending, crossed, pathway, which is located in the dorsolateral white matter (funiculus) of the spinal cord.

 

The serotonergic fibers terminate in the substantia gelatinosa of the spinal cord, a nuclear area of the dorsal horn of the spinal cord where the pain afferents synapse (see Figure 32). The descending serotonergic fibers are thought to terminate on small interneurons, which contain enkephalin. There is evidence that these enkephalin-containing spinal neurons inhibit the transmission of the pain afferents entering the spinal cord from peripheral pain receptors. Thus, descending influences are thought to modulate a local circuit.

 

There is a proposed mechanism that these same interneurons in the spinal cord can be activated by stimulation of other sensory afferents, particularly those from the touch receptors in the skin and the mechanoreceptors in the joints; these give rise to anatomically large well-myelinated peripheral nerve fibers, which send collaterals to the dorsal horn (see Figure 32). This is the physiological basis for the gate theory of pain. In this model, the same circuit is activated at a segmental level. It is useful to think about multiple gates for pain transmission.

 

We know that mental states and cognitive processes can affect, positively and negatively, the experience of pain and our reaction to pain. The role of the limbic system and the “emotional reaction” to pain will be discussed in Section D. CLINICAL ASPECT In our daily experience with local pain, such as a bump or small cut, the common response is to vigorously rub and/or shake the limb or the affected region. What we may be doing is activating the local segmental circuits via the touch- and mechano-receptors to decrease the pain sensation. Some of the current treatments for pain are based upon the structures and neurotransmitters being discussed here. The gate theory underlies the use of transcutaneous stimulation, one of the current therapies offered for the relief of pain. More controversial and certainly less certain is the postulated mechanism(s) for the use of acupuncture in the treatment of pain.

 

Most discussions concerning pain refer to ACUTE pain, or short-term pain caused by an injury or dental procedure. CHRONIC pain should be regarded from a somewhat different perspective. Living with pain on a daily basis, caused, for example, by arthritis, cancer, or diabetic neuropathy, is an unfortunately tragic state of being for many people.

 

Those involved with pain therapy and research on pain have proposed that the CNS actually rewires itself in reaction to chronic pain and may in fact become more sensitized to pain the longer the pain pathways remain active; some of this may occur at the receptor level. Many of these people are now being referred to “pain clinics,” where a team of physicians and other health professionals (e.g., anesthetists, neurologists, psychologists) try to assist people, using a variety of therapies, to alleviate their disabling condition.

03.01.16

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Francesca Frazzetto: Excelente ….

A.halim Noori

Public

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Brainstem
In the anatomy of humans and of many other vertebrates, the brainstem (or brain stem) is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. In humans it is usually described as including the medulla oblongata (myelencephalon), pons (part of metencephalon), and midbrain (mesencephalon). Less frequently, parts of the diencephalon are included. The brainstem provides the main motor and sensory innervation to the face and neck via the cranial nerves. Of the twelve pairs of cranial nerves, ten pairs come from the brainstem. Though small, this is an extremely important part of the brain as the nerve connections of the motor and sensory systems from the main part of the brain to the rest of the body pass through the brainstem.

 

This includes the corticospinal tract (motor), the posterior column-medial lemniscus pathway (fine touch, vibration sensation, and proprioception), and the spinothalamic tract (pain, temperature, itch, and crude touch). The brainstem also plays an important role in the regulation of cardiac and respiratory function. It also regulates the central nervous system, and is pivotal in maintaining consciousness and regulating the sleep cycle. The brainstem has many basic functions including heart rate, breathing, sleeping, and eating.

Structure
Midbrain
The midbrain is divided into three parts. The first is the tectum, (Latin:roof), which forms the ceiling. The tectum comprises the paired structure of the superior and inferior colliculi and is the dorsal covering of the cerebral aqueduct. The inferior colliculus, is the principal midbrain nucleus of the auditory pathway and receives input from several peripheral brainstem nuclei, as well as inputs from the auditory cortex. Its inferior brachium (arm-like process) reaches to the medial geniculate body of the diencephalon.

 

Superior to the inferior colliculus, the superior colliculus marks the rostral midbrain. It is involved in the special sense of vision and sends its superior brachium to the lateral geniculate body of the diencephalon. The second part is the tegmentum which forms the floor of the midbrain, and is ventral to the cerebral aqueduct. Several nuclei, tracts, and the reticular formation are contained here. The third part, the ventral tegmental area is composed of paired cerebral peduncles. These transmit axons of upper motor neurons.

The midbrain consists of:

  • Periaqueductal gray: The area of gray matter around the cerebral aqueduct, which contains various neurons involved in the pain desensitization pathway.

 

Neurons synapse here and, when stimulated, cause activation of neurons in the nucleus raphes magnus, which then project down into the dorsal horn of the spinal cord and prevent pain sensation transmission.
* Oculomotor nerve nucleus: This is the third cranial nerve nucleus.
* Trochlear nerve nucleus: This is the fourth cranial nerve.
* Red Nucleus: This is a motor nucleus that sends a descending tract to the lower motor neurons.
* Substantia nigra: This is a concentration of neurons in the ventral portion of the midbrain that uses dopamine as its neurotransmitter and is involved in both motor function and emotion. Its dysfunction is implicated in Parkinson’s Disease.
* Reticular formation: This is a large area in the midbrain that is involved in various important functions of the midbrain. In particular, it contains lower motor neurons, is involved in the pain desensitization pathway, is involved in the arousal and consciousness systems, and contains the locus coeruleus, which is involved in intensive alertness modulation and in autonomic reflexes.
* Central tegmental tract: Directly anterior to the floor of the 4th ventricle, this is a pathway by which many tracts project up to the cortex and down to the spinal cord.
* Ventral tegmental area: is a group of dopaminergic neurons located close to the midline on the floor of the midbrain.

Ventral view of medulla and pons
In the medial part of the medulla is the anterior median fissure. Moving laterally on each side are the pyramids. The pyramids contain the fibers of the corticospinal tract (also called the pyramidal tract), or the upper motor neuronal axons as they head inferiorly to synapse on lower motor neuronal cell bodies within the ventral horn of the spinal cord.

The anterolateral sulcus is lateral to the pyramids. Emerging from the anterolateral sulci are the CN XII (hypoglossal nerve) rootlets. Lateral to these rootlets and the anterolateral sulci are the olives. The olives are swellings in the medulla containing underlying inferior nucleary nuclei (containing various nuclei and afferent fibers). Lateral (and dorsal) to the olives are the rootlets for cranial nerves IX (glossopharyngeal), CN X (vagus) and CN XI (accessory nerve). The pyramids end at the pontine medulla junction, noted most obviously by the large basal pons. From this junction, CN VI (abducens nerve), CN VII (facial nerve) and CN VIII (vestibulocochlear nerve) emerge. At the level of the midpons, CN V (the trigeminal nerve) emerges. Cranial nerve III (the occulomotor nerve) emerges ventrally from the midbrain, while the CN IV (the trochlear nerve) emerges out from the dorsal aspect of midbrain.

Dorsal view of medulla and pons
The most medial part of the medulla is the posterior median fissure. Moving laterally on each side is the fasciculus gracilis, and lateral to that is the fasciculus cuneatus. Superior to each of these, and directly inferior to the obex, are the gracile and cuneate tubercles, respectively. Underlying these are their respective nuclei. The obex marks the end of the 4th ventricle and the beginning of the central canal. The posterior intermediate sulci separates the fasciculi gracilis from the fasciculi cuneatus. Lateral to the fasciculi cuneatus is the lateral funiculus.

Superior to the obex is the floor of the 4th ventricle. In the floor of the 4th ventricle, various nuclei can be visualized by the small bumps that they make in the overlying tissue. In the midline and directly superior to the obex is the vagal trigone and superior to that it the hypoglossal trigone. Underlying each of these are motor nuclei for the respective cranial nerves. Superior to these trigones are fibers running laterally in both directions.

 

These fibers are known collectively as the striae medullares. Continuing in a rostral direction, the large bumps are called the facial colliculi. Each facial colliculus, contrary to their names, do not contain the facial nerve nuclei. Instead, they have facial nerve axons traversing superficial to underlying abducens (CN VI) nuclei. Lateral to all these bumps previously discussed is an indented line, or sulcus that runs rostrally, and is known as the sulcus limitans. This separates the medial motor neurons from the lateral sensory neurons.

 

Lateral to the sulcus limitans is the area of the vestibular system, which is involved in special sensation. Moving rostrally, the inferior, middle, and superior cerebellar peduncles are found connecting the midbrain to the cerebellum. Directly rostral to the superior cerebellar peduncle, there is the superior medullary velum and then the two trochlear nerves. This marks the end of the pons as the inferior colliculus is directly rostral and marks the caudal midbrain.

Spinal Cord to Medulla Transitional Landmark: From a ventral view, there can be seen a decussation of fibers between the two pyramids. This decussation marks the transition from medulla to spinal cord. Superior to the decussation is the medulla and inferior to it is the spinal cord.

Development
The adult human brainstem emerges from two of the three primary vesicles formed of the neural tube. The mesencephalon is the second of the three primary vesicles, and does not further differentiate into a secondary vesicle. This will become the midbrain. The third primary vesicle, the rhombencephalon, will further differentiate into two secondary vesicles, the metencephalon and the myelencephalon. The metencephalon will become the cerebellum and the pons. The myelencephalon will become the medulla.

Function
There are three main functions of the brainstem:

  1. The brainstem plays a role in conduction. That is, all information relayed from the body to the cerebrum and cerebellum and vice versa must traverse the brainstem. The ascending pathways coming from the body to the brain are the sensory pathways, and include the spinothalamic tract for pain and temperature sensation and the dorsal column, fasciculus gracilis, and cuneatus for touch, proprioception, and pressure sensation (both of the body). (The facial sensations have similar pathways, and will travel in the spinothalamic tract and the medial lemniscus also.) Descending tracts are upper motor neurons destined to synapse on lower motor neurons in the ventral horn and posterior horn. In addition, there are upper motor neurons that originate in the brainstem’s vestibular, red, tectal, and reticular nuclei, which also descend and synapse in the spinal cord.
  2. The cranial nerves III-XII emerge from the brainstem. These cranial nerves supply the face, head, and viscera. (The first two pairs of cranial nerves arise from the cerebrum).

3.The brainstem has integrative functions being involved in cardiovascular system control, respiratory control, pain sensitivity control, alertness, awareness, and consciousness. Thus, brainstem damage is a very serious and often life-threatening problem

 

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