One of the most mysterious things in the life of a human being since time immemorial is sleep. What controls it, and how do we wake up? What keeps our body functions running even when we are in the deepest form of sleep? There is no doubt that the questions are endless. The good news is that most of these questions have been answered through research. The reticular activating system (RAS) is now believed to be a significant component of the sleep wake cycle.
The RAS was discovered in 1949. Anatomically, is composed of connections between the various nuclei found in the cortex and brainstem of mammals. These connections are in the form of reticular fibres hence the name. In the event that these area is injured resulting in damage of fibres bilaterally, the affected individuals will have problems with their sleep pattern. They are typically somnolent or lethargic.
A number of chemicals modulate the connections that exist in the system. They are termed neurotransmitters and are broadly classified into cholinergic and adrenergic. Based on the intended physiological response, these chemicals may work synergistically or competitively. A chemical called glutamate is the main cholinergic type that is involved in this process while adrenaline is the main adrenergic type. In general, an increase in the level of neurotransmitters causes increased alertness.
The mediation of sleep wake transition is undoubtedly the main function of RAS. There is a varying degree of activation depending on the depth of sleep; the deeper the sleep, the more the activation and the lighter the sleep, the less the activation. Another function is that of initiating and maintaining a state of alertness and attention whenever there is such a need. Increased blood flow to the thalamus and the midbrain during these events is evidence of this.
The RAS is central to survival. It helps in providing information that is needed immediately particularly in stressful situations. It is an entry portal for a great amount of information. At any given point in time, there are many things happening in our environment. This includes almost all forms of stimuli such as sight, touch, auditory and taste. Filtering is done and your brain will only respond to what is most important at the time.
Several factors are known to hinder the development of this important system. Preterm births are associated with a sub optimally functioning RAS. Many children delivered before their due dates have varying degrees of sleep disorders. The problem may be carried on into adulthood. Smoking during pregnancy is another factor that may disturb the system. Affected children are excessively aroused.
A number of diseases that affect the central nervous system are said to bear some relationship to a disorder of RAS. These are mainly the result of a slowing down of RAS activity which may happen with advancing age. Consequently there is a higher incidence of these diseases in the elderly compared to the general population. Examples include narcolepsy, posttraumatic stress disorder, attention deficit disorder and schizophrenia.
Several diseases that affect the central nervous system are now believed to be closely related to a dysfunction of RAS. With advancing age, there is a general decline in RAS reactivity which is why a number of these illnesses have a relatively high incidence among the geriatric population. Diseases that may fall under this category include schizophrenia, post traumatic stress disorder, narcolepsy, attention deficit disorder and many others.
The RAS was discovered in 1949. Anatomically, is composed of connections between the various nuclei found in the cortex and brainstem of mammals. These connections are in the form of reticular fibres hence the name. In the event that these area is injured resulting in damage of fibres bilaterally, the affected individuals will have problems with their sleep pattern. They are typically somnolent or lethargic.
A number of chemicals modulate the connections that exist in the system. They are termed neurotransmitters and are broadly classified into cholinergic and adrenergic. Based on the intended physiological response, these chemicals may work synergistically or competitively. A chemical called glutamate is the main cholinergic type that is involved in this process while adrenaline is the main adrenergic type. In general, an increase in the level of neurotransmitters causes increased alertness.
The mediation of sleep wake transition is undoubtedly the main function of RAS. There is a varying degree of activation depending on the depth of sleep; the deeper the sleep, the more the activation and the lighter the sleep, the less the activation. Another function is that of initiating and maintaining a state of alertness and attention whenever there is such a need. Increased blood flow to the thalamus and the midbrain during these events is evidence of this.
The RAS is central to survival. It helps in providing information that is needed immediately particularly in stressful situations. It is an entry portal for a great amount of information. At any given point in time, there are many things happening in our environment. This includes almost all forms of stimuli such as sight, touch, auditory and taste. Filtering is done and your brain will only respond to what is most important at the time.
Several factors are known to hinder the development of this important system. Preterm births are associated with a sub optimally functioning RAS. Many children delivered before their due dates have varying degrees of sleep disorders. The problem may be carried on into adulthood. Smoking during pregnancy is another factor that may disturb the system. Affected children are excessively aroused.
A number of diseases that affect the central nervous system are said to bear some relationship to a disorder of RAS. These are mainly the result of a slowing down of RAS activity which may happen with advancing age. Consequently there is a higher incidence of these diseases in the elderly compared to the general population. Examples include narcolepsy, posttraumatic stress disorder, attention deficit disorder and schizophrenia.
Several diseases that affect the central nervous system are now believed to be closely related to a dysfunction of RAS. With advancing age, there is a general decline in RAS reactivity which is why a number of these illnesses have a relatively high incidence among the geriatric population. Diseases that may fall under this category include schizophrenia, post traumatic stress disorder, narcolepsy, attention deficit disorder and many others.
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