#nervous system

• Acanthesthesia — A form of paresthesia or subjective disturbance of tactile and painful sensitivity, characterized by a false, spontaneous, and unpleasant sensation of pinpricks or thorn-like pricks on the skin, occurring in the absence of any external mechanical stimulus. This neurological symptom is typically associated with damage to peripheral nerve fibers, being encountered in neuropathies, radiculopathies, or lesions of the sensory pathways in the spinal cord.
• Nociceptor — A specialized, branched free nerve ending responsible for receiving and transforming harmful stimuli (mechanical, extreme thermal, or chemical tissue damage) into painful electrical impulses transmitted to the brain; a nociceptor. These peripheral receptors are widely distributed across the skin and joints.
• Alloesthesia — A neurological disorder of sensory perception where a stimulus applied to a specific part of the body is structurally felt on the opposite side or in a completely different location than the actual one; this cortical or radicular dysfunction affects the correct localization of tactile or painful sensations.
• Amphetamine — A synthetic chemical substance with an aromatic amine structure, possessing a potent stimulant effect on the central nervous system by enhancing the release of dopamine and norepinephrine. From a clinical perspective, it is used under strict medical control to treat attention deficit hyperactivity disorder (ADHD) and narcolepsy, but carries a high potential for abuse, severe psychological dependence, and cardiovascular toxicity, being legally classified as a controlled psychotropic substance.
• Amphicyte — A flattened, satellite-type glial cell that structurally surrounds and protects the body of neurons within the spinal and autonomic nerve ganglia of the peripheral nervous system. These capsular satellite cells play an essential role in maintaining the biochemical microenvironment, providing trophic support, and ensuring the electrical insulation of the neuronal cell body.
• Amphineuran — Belonging or relating to amphineurans (class Amphineura), a class of primitive marine mollusks with bilateral symmetry and a nervous system composed of parallel cords; as a noun, it designates a representative of this group of mollusks (such as chitons or placophorans) structurally characterized by a shell of articulated calcareous plates or a vermiform body.
• Amphotonia — A pathological or functional state characterized by the simultaneous or alternating increase in tone within both branches of the autonomic nervous system (both the sympathetic and parasympathetic systems). This structural disorder of neurovegetative homeostasis can cause oscillating and unpredictable clinical manifestations in internal organs.
• Amyelia — An extremely rare and severe congenital malformation within the neural tube defects spectrum, characterized by the total absence or complete developmental arrest of the spinal cord. This severe structural anomaly occurs during the first weeks of embryogenesis due to the failure of the posterior neuropore to close, being incompatible with extrauterine life and often associated with other major cranial malformations.
• Unmyelinated — Lacking a myelin sheath; a nerve fiber or axon devoid of the protective, insulating structural lipid layer. Amielinic (unmyelinated) fibers (such as type C fibers) are characterized by a significantly slower nerve impulse conduction velocity compared to myelinated ones, playing an essential functional role in transmitting dull pain sensations, temperature, and regulating autonomic nervous system connections.
• Analeptic — A substance or medication with a potent stimulating action on the central nervous system, structurally utilized to revitalize vital functions, particularly to stimulate respiratory and circulatory centers in the brainstem. In a precise clinical sense, these compounds (such as caffeine or doxapram) are administered in cases of respiratory collapse, acute intoxications with depressants, or to shorten the post-anesthetic coma period.
• Anarthria — An extreme clinical form of dysarthria, characterized by the complete loss of the ability to articulate words and pronounce speech sounds, resulting from a severe lesion of the central or peripheral nervous system (such as strokes, head traumas, or neurodegenerative diseases). In neurological semiology, this structural disorder exclusively affects the motor function of the muscles involved in phonation, while language comprehension and writing capabilities remain intact.
• Angioblastoma — A vascular tumorous formation, either benign or of low malignancy, characterized by the abnormal and uncontrolled proliferation of angioblasts or immature endothelial cells. In oncological and histopathological terminology, this structural term often refers to hemangioblastoma, a tumor frequently localized within the central nervous system (cerebellum or spinal cord), potentially associating ectopic erythropoietin secretion and compressive neurological manifestations.
• Angioglioma — A rare and complex brain tumorous formation of a mixed nature, structurally composed of a proliferative glial component (glioma) and a dense, rich network of newly formed blood vessels (angiomatous component). This well-defined oncological lesion, localized predominantly within the central nervous system, often poses difficulties in differential histopathological diagnosis and requires strict imaging monitoring due to the risk of intracranial hemorrhage or perifocal edema.
• Antideliriant — A medication, substance, or treatment that combats, alleviates, or eliminates delirium, psychotic episodes, and hallucinations; a neuroleptic or antipsychotic. As an adjective, it describes the structural therapeutic effect of a pharmaceutical preparation to restore cognitive clarity and stabilize the activity of the central nervous system during severe mental disorders.
• Antidepressant — A medication, chemical substance, or treatment used to combat, alleviate, and prevent states of depression, anxiety disorders, and clinical episodes of deep sadness or apathy. As an adjective, it describes the structural therapeutic effect of a compound capable of regulating the concentration of neurotransmitters (serotonin, norepinephrine, dopamine) at the level of neuronal synapses within the central nervous system.
• Antidepressive — Combating depression, eliminating states of anxiety, and regulating altered psychic tone; currently used as a noun to designate a medication intended for treating major or minor depressive episodes. It acts structurally at the level of brain receptors to alleviate feelings of hopelessness, chronic mental fatigue, and emotional lability.
• Antihypnotic — Combating sleep, drowsiness, or the effects induced by hypnotic drugs; a central nervous system stimulant substance that induces wakefulness and alertness. In a clinical sense, it intervenes structurally by blocking sleep-promoting receptors or by stimulating the release of excitatory neurotransmitters such as dopamine and noradrenaline.
• Antiparalytic — Combating, preventing, or ameliorating paralysis or its destructive effects on the neuromuscular system; a medicinal substance or therapeutic treatment structurally designed to stimulate nerve conduction and restore affected muscle tone. In a clinical sense, it describes neuroprotective substances that prevent the degradation of motor neurons and support the functional recovery of limbs.
• Anxiety — An unpleasant and diffuse emotional state, characterized by feelings of apprehension, indeterminate fear, insecurity, and internal tension in the absence of a real or imminent threat; a complex psychological and physiological reaction that often includes vegetative symptoms such as palpitations, intense sweating, tremors, and shallow breathing.
• Anxiolytic — Diminishing, calming, or suppressing a state of anxiety and mental tension; (noun) a medicinal substance or pharmaceutical preparation used in the treatment of anxiety disorders, acting on the central nervous system to restore emotional balance.