The reticular activating system (RAS) is one of the most important parts of the brain. This article is a short introduction to the system’s functions and the way it influences human behavior.
The Brain’s Ignition System
The reticular activating system (RAS) acts like the ignition system of the brain, that awakens an individual from sleep to a state of heightened awareness.
Every conscious or unconscious function of the mind can be traced back or mapped to some part of the brain, which is one of the most complex organizations of matter in the universe. The mind is projected by the brain and its every process has an origin in some actual neuronal network.
This article talks about a brain region that significantly affects cognition and plays a large role in the sleep-wake transition.
Research in neuroscience has revealed, that the reticular activating system (RAS) is responsible for many cognitive functions related to awareness. This was revealed through study of mammalian brains. Evolutionarily, it is one of the oldest regions and it plays a big role in shaping the survival instinct in humans, besides acting as a bridge between the higher and lower parts of the brain.
Let us explore the location, structure, and functions of this system, which is also known as extrathalamic control modulatory system or bulboreticular facilitatory area.
Location and Structure
The reticular activating system connects the brain stem, to the cerebral cortex, through various neural paths. The stem controls most of the involuntary functions, as well as reflexes of the body, while the cerebral cortex is the seat of consciousness and thinking abilities. The system forms a link between these two different regions, helping our consciousness put together an internal world, through assimilation of sensory information, gathered from all body parts.
The system projects out of the brain stem, through the thalamus, to connect with the cerebral cortex. The neurons from the stem radiate upwards and terminate at the thalamus, at diffuse thalamic nuclei, which in turn, project further into the cerebrum. The system also involves neurons projecting out of the sensory pathways, directly into the sensory cortex.
Studies have revealed that there are two most important parts of the RAS. One is the ascending system (which has connections with the cerebral cortex, hypothalamus, and thalamus) and the other is the descending system (which is connected to the cerebellum and many sensory nerves).
A large part of the system consists of brain parts that are responsible for our survival instincts. Hence, it has a deep connection with awareness functions of the brain. The main parts which constitute the RAS are:
- Reticular Formation in the Midbrain
- Mesencephalon (Mesencephalic Nucleus)
- Dorsal Hypothalamus
- Thalamic Intralaminar Nucleus
- Tegmentum
RAS functions are controlled by certain cholinergic (related to acetylcholine) and adrenergic (related to Adrenaline) neurotransmitters. In terms of neuron grouping, this brain region constitutes the raphe nucleus, the pedunculopontine nucleus, and the locus caeruleus, all situated in the brain stem. For the sensory signals traveling towards and away from the cerebrum, this system acts as the gateway. In fact, the nerve fibers of this region are known to make the connection betweenbody and mind. For the RAS to be triggered, signal activity needs to occur in the sensory pathways, that are connected with it.
Functions
Relays Sensory Signals
In a state of wakefulness, all the sensory information that reaches the brain stem (including touch, smell, visual, and temperature signals), from the various afferent nerves, is transmitted via this system, to the cerebrum for processing, after undergoing filtering. Pain felt in any part of the body, is relayed through the reticular formation.
The Flight or Fight Response
When we encounter a threat, that demands immediate defensive or offensive action, the electrical signals from sensory neurons are relayed to the cerebral cortex for processing, via the RAS.
Regulates Sleep-Wake Transitions
One of the major functions of this specialized brain circuitry is the regulation of transition between sleep and wakefulness. The transition that we make from deep sleep to being fully awake and functional, as well as the reverse function, is controlled by this region. This functionality is mediated through the monoaminergic and cholinergic pathways.
All the mind’s functions manifest themselves physically, as electrical activity in the brain. The transition from sleep to wakefulness is therefore a change in the electrical activity associated with certain brain regions, measured in terms of frequency of the electrical signals. The state of wakefulness in humans, is associated with low-voltage fast burst brain waves. The same kind of waves are also associated with the REM (Rapid Eye Movement) phase during sleep. On the other hand, during non-REM sleep, the activity of high-voltage slow waves is predominant. The RAS orchestrates the transition from sleep to wakefulness, by promoting the creation of gamma band (20-40 Hz) waves and suppressing slow waves in the brain, like the spindle wave oscillations (11-14 Hz), delta waves (1-4 Hz), and slow waves in the cortex (0.3-1 Hz). This transition is reversible. Sleep is possible, only through the suppression of RAS activity, that is, through a reduction of afferent nerve activity, which transmits sensory signals to the cortex.
During non-REM sleep, which is mostly dreamless, RAS is shut down, thus cutting off connections with sensory inputs. This inhibition of the system is facilitated by the preoptic nucleus neurons.
Controls Focusing Ability
The ability to filter out information from external sources and focus on one particular fact, detail, or thought is controlled by this brain region. If it weren’t for this circuitry, our consciousness would be overwhelmed and flooded with all sensory information, leading to an inability to make decisions. The system helps in prioritizinginformation and controls what appears in the mind’s eye, at any point of time.
Recent research has revealed that this region is also responsible for bringing your mind into periods of heightened attention, alertness, or higher focus. This function is primarily mediated by the reticular formation and the thalamic intralaminar nuclei, which experience an increased blood flow, during these times.
Coordinated Response to External Stimuli
It is responsible for providing an integrated (cardiovascular, respiratory, and motor) response to external stimuli. It also controls coordination during walking, sexual functions, and eating.
Motor Control
Connections of the reticular formation with motor neurons facilitates maintenance of balance, posture, and tone, when executing various body movements. It enables the cerebellum to integrate vestibular, visual, and audio inputs, to process the data for motor coordination.
Muscle Atonia During REM Sleep
This system also plays a role in REM sleep, when we experience dreams. It is responsible for muscle atonia (temporary paralysis or relaxation of muscles) experienced during these phases.
Habituation
Not only does RAS filter out information, but it also learns to identify patterns in the sensory signals transmitted through it. The reticular formation gets habituated to excluding meaningless and repetitive signals, that are deemed to be consistently unimportant. That explains why people can sleep through any kind of noise, once they have become habituated to it, while waking up in a startled state, to an auditory signal like a gunshot.
Helps Regulate Circadian Rhythm
The raphe nuclei, a part of the reticular formation, work with thesuprachiasmatic nucleus (SCN) to maintain the circadian rhythm. It provides information about the level of alertness of the individual to the SCN, for it to act accordingly.
Damage to this system can lead to a transition into coma. Because of its positioning at the back of the brain, this area is very vulnerable to damage during accidents. Brain researchers have linked disorders in the RAS to attention deficit disorders, Alzheimer’s disease, narcolepsy, and sleep disorders.
Anesthetics and psychotropic drugs directly affect this system, causing a transition into unconsciousness or semi-consciousness. There is a relation between our action of setting goals and the RAS, as it controls the ability to focus and sift through incoming information. Overall, it manages the transition between levels of consciousness and controls what we prioritize as our current reality.
FAQs
What is the main function of the reticular activating system? ›
The reticular activating system (RAS) is a complex bundle of nerves in the brain that's responsible for regulating wakefulness and sleep-wake transitions. 1 It functions as a filter out unnecessary noise that can interfere with the processing of messages or slow the processing of messages during sleep.
What is the structure and function of the reticular formation? ›The reticular formation contains long ascending (i.e. traveling to the brain) and descending (i.e. traveling from the brain to the body) tracts. The descending projections are primarily involved with the modulation of sensory and motor pathways.
What is the structure of the reticular? ›Reticular dermis: The reticular layer is the bottom layer of your dermis. It's thick, and it contains blood vessels, glands, hair follicles, lymphatics, nerves and fat cells. A net-like structure of elastin fibers and collagen fibers surrounds the reticular dermis.
What is the function of the reticular activating system RAS quizlet? ›Terms in this set (2)
A network of neurons extending from the top of the spinal cord up to the thalamus; filters incoming sensory stimuli and redirects them to the cerebral cortex, activating the cortex and influencing our state of physiological arousal and alertness.
AN EXAMPLE OF THE RAS AT WORK
The study found that both parents would sleep right through a plane taking off nearby (extremely loud). Yet the mother would wake up if the baby stirred in the next room (comparatively, a much lower sound level). And that's the Reticular Activating System at work.
The RAS and its associated structures exist primarily within the hypothalamus and brainstem. The hypothalamus receives vascular perfusion mainly by branches of the circle of Willis, which sits inferiorly to the hypothalamus.
What is the function of the reticular formation quizlet? ›maintains levels of alertness and sleep. Also functions as a filter for inattention to repetitive meaningless stimuli.
How do you activate the reticular activating system? ›Use facial expressions to make silent commentary on the insightfulness of the question, put your index finger to your chin and look off into space, or widen your eyes as you wait. Use humor or an anecdote. Humor is a jolt to the RAS. Use topic-related visual aids as you talk such as photographs, cartoons or charts.
What is the reticular formation and where is it located? ›The reticular formation is located in the tegmentum of the brainstem. It contains several nuclei and descending and ascending tracts. Caudal and rostral regions are formed by the division of the region of the reticular formation.
What is the main function of reticular connective tissue? ›The reticular connective tissues are found in the kidney, the spleen, lymph nodes, and bone marrow. Their function is to form a stroma and provide structural support, such as that in the lymphoid organs, e.g. red bone marrow, spleen, and lymph node stromal cells.
What is a function of reticular connective tissue quizlet? ›
Reticular connective tissue forms an internal scaffolding for certain organs, such as lymph nodes, bone marrow, and the spleen. This scaffolding supports other cell types including white blood cells, mast cells, and macrophages.
What is the reticular activating system quizlet? ›Reticular activating system (RAS) A network of neurons extending from the top of the spinal cord up to the thalamus; filters incoming sensory stimuli and redirects them to the cerebral cortex, activating the cortex and influencing our state of physiological arousal and alertness.
What is the main function of the reticular formation which connects to the reticular activating system quizlet? ›Function: The ascending reticular formation is also called the reticular activating system. It is responsible for the sleep-wake cycle, thus mediating various levels of alertness.
Which part of the brain is responsible for consciousness answers? ›The cerebrum is the largest brain structure and part of the forebrain (or prosencephalon). Its prominent outer portion, the cerebral cortex, not only processes sensory and motor information but enables consciousness, our ability to consider ourselves and the outside world.
Does the reticular activating system control consciousness? ›The ascending reticular activating system from pontine reticular formation to the thalamus in the human brain. Introduction: Action of the ascending reticular activating system (ARAS) on the cerebral cortex is responsible for achievement of consciousness.
What happens when the RAS is damaged? ›Damage to the RAS causes unconsciousness, resulting in not being awake or aware. Along the length of the brainstem, there are midline raphe nuclei and two lateral types of nuclei: the medial group of nuclei and the small group of nuclei.
What happens when the reticular activating system is damaged? ›The reticular activating system is the part of the brain that maintains the sleep/wake cycle. Any damage to this region can cause hypersomnolence and drowsiness along with altered sensorium.
What does RAS stand for in the brain? ›RAS (Reticular Activating System)
Who discovered the reticular activating system? ›Abstract. Discovery of the ascending reticular activating system (ARAS) can be attributed to work done in research neuroscientist Horace Magoun's laboratory.
What does RAS stand for? ›| Acronym | Definition |
|---|---|
| RAS | Risk Assessment Standards (auditing) |
| RAS | Risk Analysis Service |
| RAS | Row Access Strobe (less common) |
| RAS | Remote Administration Software |
What is the main function of the reticular formation group of answer choices? ›
The overall functions of the reticular formation are modulatory and premotor, involving somatic motor control, cardiovascular control, pain modulation, sleep and consciousness, and habituation.
What are the functions of neurons in the reticular formation? ›The reticular formation consists of more than 100 small neural networks with varied functions including motor control, cardiovascular control, pain modulation, sleep, and habituation. Bilateral damage to the reticular formation of the midbrain may lead to coma or death.
What is reticular formation in psychology? ›Definition of reticular formation
: a mass of nerve cells and fibers situated primarily in the brain stem that plays an important role in controlling autonomic functions (such as respiration), reflexive movement, posture and balance, and consciousness and the sleep-wake cycle.
The Reticular Activating System (RAS), which is in the lower part of the posterior brain, filters all incoming stimuli and makes the “decision” as to what people attend to or ignore.
What part of the brain is involved in arousal and attention? ›We conclude that the thalamus is involved in mediating the interaction of attention and arousal in humans. The relationship between arousal and attention is closely related to the functions of consciousness (Posner, 1994; Harth, 1995).
What is reticular formation in the brain? ›The reticular formation is a complex network of brainstem nuclei and neurons that serve as a major integration and relay center for many vital brain systems to coordinate functions necessary for survival.
What are the functions of reticular fibers? ›Reticular fibers crosslink to form a fine meshwork (reticulin). This network acts as a supporting mesh in soft tissues such as liver, bone marrow, and the tissues and organs of the lymphatic system.
Where is reticular connective tissue found in the body? ›Reticular connective tissue is found around the kidney, liver, the spleen, and lymph nodes, Peyer' patches as well as in bone marrow.
What type of cells are found in reticular tissue? ›Reticular connective tissue is named for the reticular fibers which are the main structural part of the tissue. The cells that make the reticular fibers are fibroblasts called reticular cells. Reticular connective tissue forms a scaffolding for other cells in several organs, such as lymph nodes and bone marrow.
What is the structure of reticular connective tissue? ›Reticular tissue is a special type of connective tissue that predominates in various locations that have a high cellular content. It has a branched and mesh-like pattern, often called reticulum, due to the arrangement of reticular fibers (reticulin). These fibers are actually type III collagen fibrils.
What is a function of reticular connective tissue quizlet Chapter 20? ›
The loose organization of reticular connective tissue provides niches for macrophages and lymphocytes. Lymph filters through the nodes and is exposed to lymphocytes and macrophages.
Where is reticular connective tissue found in the body quizlet? ›Reticular connective tissue is found around the liver, the kidney, the spleen, and lymph nodes, as well as in bone marrow.
What is the function of the reticular formation quizlet? ›maintains levels of alertness and sleep. Also functions as a filter for inattention to repetitive meaningless stimuli.
What would happen if the reticular activating system was damaged? ›The reticular activating system is the part of the brain that maintains the sleep/wake cycle. Any damage to this region can cause hypersomnolence and drowsiness along with altered sensorium.
What does RAS stand for? ›RAS (Reticular Activating System)
What is reticular formation in psychology? ›Definition of reticular formation
: a mass of nerve cells and fibers situated primarily in the brain stem that plays an important role in controlling autonomic functions (such as respiration), reflexive movement, posture and balance, and consciousness and the sleep-wake cycle.
Reticular activating system (RAS) A network of neurons extending from the top of the spinal cord up to the thalamus; filters incoming sensory stimuli and redirects them to the cerebral cortex, activating the cortex and influencing our state of physiological arousal and alertness.
What is the main function of the reticular formation group of answer choices? ›The overall functions of the reticular formation are modulatory and premotor, involving somatic motor control, cardiovascular control, pain modulation, sleep and consciousness, and habituation.
What is the main function of the reticular formation which connects to the reticular activating system quizlet? ›Function: The ascending reticular formation is also called the reticular activating system. It is responsible for the sleep-wake cycle, thus mediating various levels of alertness.
How is the reticular activating system controlled? ›Use facial expressions to make silent commentary on the insightfulness of the question, put your index finger to your chin and look off into space, or widen your eyes as you wait. Use humor or an anecdote. Humor is a jolt to the RAS. Use topic-related visual aids as you talk such as photographs, cartoons or charts.
What part of the brain controls sleep and arousal? ›
The hypothalamus, a peanut-sized structure deep inside the brain, contains groups of nerve cells that act as control centers affecting sleep and arousal.
Who discovered the reticular activating system? ›Abstract. Discovery of the ascending reticular activating system (ARAS) can be attributed to work done in research neuroscientist Horace Magoun's laboratory.
What does RAS stand for in the brain? ›Meet the Reticular Activating System (RAS)! Reticular means “net or web-like.” The RAS is a net-like formation of nerve cells and their connections lying deep within the brainstem, between the brain and the spinal cord.
What drugs inhibit RAS? ›ACE-inhibitors (benazepril, captopril, cilazapril, delapril, enalapril, fosinopril, imidapril, lisinopril, moexipril, perindopril, quinapril, ramipril, spirapril, trandolapril or zofenopril) and the direct renin inhibitor aliskiren block the actions of specific enzymes involved in the production of angiotensin II in ...
What is RAS in cell signaling? ›Ras, from "Rat sarcoma virus", is a family of related proteins that are expressed in all animal cell lineages and organs. All Ras protein family members belong to a class of protein called small GTPase, and are involved in transmitting signals within cells (cellular signal transduction).
What is an example of reticular? ›The reticular fibers form a labyrinth-like stroma to support free blood cells (large lymphocytes) in many lymphoid organs. Examples of lymphoid organs containing reticular fibers are lymph nodes, red bone marrow, and spleen.
Is reticular formation sensory? ›Efferent fibers from the reticular formation can convey sensory information to the cortex of a sleeping individual, which would awaken that person.