The state of being unconscious, e.g. as a result of lack of oxygen or from some other external cause such as a blow on the head.
State of complete or partial unawareness of the surroundings and lack of response to sensory stimuli. It may be caused by many conditions, including shock; lack of respiratory efficiency; drags or poisons; many metabolic disorders, including severe electrolyte imbalance; severe hypoglycemia; and kidney failure; as well as trauma, seizures, tumors, and other causes.
A condition of being unaware of one’s surroundings, as in sleep, or of being unresponsive to stimulation. An unnatural state of unconsciousness may be caused by factors that produce reduced brain activity, such as lack of oxygen, a blow on the head, poisoning, blood loss, and many diseases, or it may be brought about deliberately during general anesthesia.
The brain is the organ of the mind. Normal conscious alertness depends upon its continuous adequate supply with oxygen and glucose, both of which are essential for the brain cells to function normally. If either or both of these are interrupted, altered consciousness results. Interruption may be caused by three broad types of process affecting the brain stem: the reticular formation (a network of nerve pathways and nuclei-connecting sensory and motor nerves to and from the cerebrum, cerebellum, spinal cord and cranial nerves) and the cerebral cortex. The three types are diffuse brain dysfunction for example, generalized metabolic disorders such as uraemia, hypoglycaemia, or toxic disorders such as septicaemia; direct effects on the brain stem as a result of infective, cancerous or traumatic lesions; and indirect effects on the brain stem such as a tumour or oedema in the cerebrum creating pressure within the skull. Within these three divisions are a large number of specific causes of unconsciousness.
The state of being partly or completely unaware of external stimuli. Unconsciousness occurs normally in sleep, and pathologically, in such conditions as syncope (fainting), shock, unper-fused cardiac dysrhythmias, and intoxications.
An atypical state characterized by a diminished awareness of self and the surroundings, caused by decreased activity in the brainstem’s reticular formation. An individual who is unconscious can be awakened with considerable effort or might remain unresponsive. Unconsciousness can take the form of brief and mild episodes, such as fainting or concussion, or it can be profound and extended.