Reticular Formation

Reticular Formation

Introduction

Good morning sunshine. Welcome to today’s encourage Mint, meant to freshen your day. Today is going to be about two minutes or so, so hang in there, it’s really interesting stuff. So today is all about the reticular activating system. RAS for short, you can Google it or YouTube it to find out more information on it.

So what it is, it’s a group of nerves in the-base of your brain and they act together to filter out 99.9% of all the information around us that we see, smell, or hear, and there’s so much information around us we can only like our conscious mind can only take so much information in, and this group of nerves filters everything out so we could focus in,which makes sense, we need that in our lives. And so an example of the reticular activating system is when you are looking for a car for me personally I’m looking for a Honda Element right now because I believe it’s the perfect car for my needs right so I did all this searching and read reviews and I focusedin and internally I’ve decided this is the car that would best suit me at this time in my life and so what happened and you can relate to this I started seeing Honda elements everywhere in my life I didn’t try to see them they just started popping up everywhere now they didn’t magically appear it’s the reticular activating system which I just learned about that’ sallowing this them to come through the filter and now I see them everywhere I don’t see every other car just those cars so how does this work in the rest of my life well I know that I have to do an encouragement every morning I’ve kind of like made it a little goal of mine at this point and so now I’m starting to see these positive encouraging things in every moment of my life and then I just put them on a little app in my phone so remember the positive,encouraging thing out of any situation. And they’re just popping up everywhere because I’ve decided that I’m focusing in on positivist.

And so, I want to encourage you today … focus in on the positive things of every part of life and that stuff’s going to start … your going to start seeing it everywhere. You know, if it’s opportunities, opportunities to make more income for yourself,if you’re focusing in on “how can I make more income?,” and are searching out and start to make it internal, you’re going to start to see these opportunities just popping up everywhere because you’re now focused on it, and the reticular activating system is letting that stuff through now, because you’re now focused on it.

A diffuse network of nerve pathways in the brain stem connecting the spinal cord, cerebrum, and cerebellum, and mediating the overall level of consciousness.
1. Diffuse ill-definesd masss of nerve cell clusters and interlacing nerve fibers occupying entire core of brain stem
2. L/M appearance of a vague network of nerve cell n fibers
3. On stimulation produce Arousal
4. Phylogenentically…old reticular core of brain
5. Diffuse arrangemenet of Neurons…Primitive vertebrates
6. Sleep-wake cycle
7. Level of consciousness
8. Alterness

The reticular formation is divided into three columns: raphe nuclei (median), gigantocellular reticular nuclei (medial zone), and parvocellular reticular nuclei (lateral zone).
The raphe nuclei are the place of synthesis of the neurotransmitter serotonin, which plays an important role in mood regulation. The gigantocellular nuclei are involved in motor coordination.
The parvocellular nuclei regulate exhalation.

Contents
1. Topographical classification
      1.1 Medial and lateral reticular formation                                                                                                                           1.2 Function                                                                                                                                                                        2.   Projection Fibers                                                                                                                                                                3.  Ascending reticular activating system                                                                                                                                    3.1 Structure of ARAS                                                                                                                                                               3.2 Function of ARAS

1.Topographical classification

The reticular formation nuclei are found deep within the brainstem, along its length. It is easier to appreciate the approximate location of these nuclei if they are superimposed on a posterior view of the brainstem with the cerebellum removed.

1.1 Medial and lateral reticular formation
The medial reticular formation and lateral reticular formation are two columns of nuclei with ill-defined boundaries that send projections through the medulla and into the midbrain. The nuclei can be differentiated by function, cell type, and projections of efferent or afferent nerves. Moving caudally from the rostral midbrain, at 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 nerves, which serve to mediate their characteristic reflexes and functions.

1.2 Function
While it may be a fairly small part of your brain, the RAS has a very important role: it’s the gatekeeper of information that is let into the conscious mind. This little bit of brain matter is responsible for filtering the massive amounts of information your sensory organs are constantly throwing at it and selecting the ones that are most important for your conscious mind to pay attention to. Why do we need this little gatekeeper? Well, your senses are constantly feeding so much information to your brain that you can’t possibly pay attention to all of it. The RAS never gets a break!

Try to see just how much information you pick up every minute. Take ten seconds and listen to every sound around you that you can perceive…you’ll be surprised at what you miss on a regular basis, but this is because your RAS decides what is important and what can be safely ignored. This doesn’t just happen with sounds. Our skin is roughly 20 square feet that abounds with around a million nerve cells detecting pressure, pain, temperature, and location. And a human eye captures more than 300 megapixels of visual information every second!

Despite all of this sensory information, it’s estimated that the conscious mind can only handle slightly more than 100 pieces of information every second. There’s a tremendous amount of paring down that needs to happen between your senses and your conscious mind. Your RAS is the way evolution has decided to handle this excessive information problem. It is uniquely suited to distinguish between relevant and irrelevant pieces of information. For example, it distinguishes between the honk of a car right next to you and one far down the street, or it tells a husband, ‘Unless you want a fight, you better pay attention to what your wife just said!’

Not only does it do all of that, the RAS also plays an important role in motivation and goal setting. Not bad for something tiny nestled close to your brain stem!

2. Projection Fibers

The dendrites and axons of the reticular formation are atypical when compared to those of other neurons. The axons are extremely long and can reach sites far removed from their cell bodies. The dendrites are polysynaptic, giving rise to the reticular formation being described as a non-specific unit. Both efferent and afferent fibers interact with the reticular formation to regulate its own action and the action of other neuronal systems.

The reticular formation has afferent sensation from the spinothalamic (temperature sensation, fine touch and pain) and dorsal column-medial lemniscus (proprioception, vibration and position sense, and crude touch) pathways. It modifies information from the vestibular tract, thus assisting with the regulation of antigravity muscle tone while standing.

There are also efferent fibers associated with the reticular formation. These include the reticulobulbar (pain regulation) and reticulospinal (locomotion and postural regulation) tracts that regulate sensory information in the peripheral nervous system.

Examples Of Projection Fibers

Visual Pathways, and the Cortico-spinal or pyramidal tract

3. Ascending reticular activating system
The ascending reticular activating system (ARAS), also known as the extrathalamic control modulatory system or simply the reticular activating system (RAS), is a set of connected nuclei in the brains of vertebrates that is responsible for regulating wakefulness and sleep-wake transitions. The ARAS is a part of the reticular formation and is mostly composed of various nuclei in the thalamus and a number of dopaminergic, noradrenergic, serotonergic, histaminergic, cholinergic, and glutamatergic brain nuclei

3.1 Structure of ARAS
The ARAS is composed of several neural 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 ARAS is a collection of different nuclei – more than 20 on each side in the upper brainstem, the pons, medulla, and posterior hypothalamus. The neurotransmitters that these neurons release include dopamine, norepinephrine, serotonin, histamine, acetylcholine, and glutamate. They exert cortical influence through direct axonal projections and indirect projections through thalamic relays.

The thalamic pathway consists primarily of cholinergic neurons in the pontine tegmentum, whereas the hypothalamic pathway is composed primarily of neurons that release monoamine neurotransmitters, namely dopamine, norepinephrine, serotonin, and histamine.The glutamate-releasing neurons in the ARAS were identified much more recently relative to the monoaminergic and cholinergic nuclei; the glutamatergic component of the ARAS includes one nucleus in the hypothalamus and various brainstem nuclei. The orexin neurons of the lateral hypothalamus innervate every component of the ascending reticular activating system and coordinate activity within the entire system

3.2Function of ARAS
While it may be a fairly small part of your brain, the RAS has a very important role: it’s the gatekeeper of information that is let into the conscious mind. This little bit of brain matter is responsible for filtering the massive amounts of information your sensory organs are constantly throwing at it and selecting the ones that are most important for your conscious mind to pay attention to. Why do we need this little gatekeeper? Well, your senses are constantly feeding so much information to your brain that you can’t possibly pay attention to all of it. The RAS never gets a break!

Try to see just how much information you pick up every minute. Take ten seconds and listen to every sound around you that you can perceive…you’ll be surprised at what you miss on a regular basis, but this is because your RAS decides what is important and what can be safely ignored. This doesn’t just happen with sounds. Our skin is roughly 20 square feet that abounds with around a million nerve cells detecting pressure, pain, temperature, and location. And a human eye captures more than 300 megapixels of visual information every second!

Despite all of this sensory information, it’s estimated that the conscious mind can only handle slightly more than 100 pieces of information every second. There’s a tremendous amount of paring down that needs to happen between your senses and your conscious mind. Your RAS is the way evolution has decided to handle this excessive information problem. It is uniquely suited to distinguish between relevant and irrelevant pieces of information. For example, it distinguishes between the honk of a car right next to you and one far down the street, or it tells a husband, ‘Unless you want a fight, you better pay attention to what your wife just said!’

Not only does it do all of that, the RAS also plays an important role in motivation and goal setting. Not bad for something tiny nestled close to your brain stem!

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SUMMARY

ARAS, thalamocortical, and basal forebrain-cortical arousal systems activate the forebrain regions involved in dream construction in a manner that is chemically and anatomically different from waking. In REM sleep, such activation may be more frequent and sustained and, perhaps, may proceed through different or more diverse pathways than in NREM sleep. Cortical circuits activated in REM-sleep dreaming are medial circuits linking visual association and paralimbic regions (central crescent in Figure 51-1), but not the primary sensory and lateral frontal executive cortical regions that are active in waking.36 Therefore dreaming is both positively and negatively emotionally salient (amygdala, ventral striatum, vmPFC), often conflictual (anterior cingulate) and social (vmPFC), while also displaying profoundly deficient working memory, orientation, and logic (lateral prefrontal and parietal deactivation). Subcortical circuits involving the limbic structures, striatum, diencephalon, and brainstem regions are selectively activated in REM sleep. They may contribute to dreaming’s emotional (limbic subcortex), motoric (striatum, brainstem, cerebellum), instinctual (hypothalamus), and motivational (midbrain-ventral striatum) properties. Preserved connectivity in default-mode network simulation subsystem during REM sleep may be the neural substrate of dream simulations, whereas altered connectivity in default-mode network self-referential subsystem may underlie the high degree of delusional acceptance of dreams compared to waking cognition.

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