| gamma motor system | The reflex arc consisting of small anterior horn cells and neuroma, their small fibres projecting to the intrafusal bundle producing its contraction, which initiates the afferent impulses that pass through the posterior root to the anterior horn cells, inducing a stretch reflex. Synonym: gamma motor neurons, gamma motor system, Granit's loop. (05 Mar 2000) |
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| gamma-glutamate (glutamate gamma-) carboxypeptidase | N-Pteroyl-l-glutamate hydrolase;an enzyme cleaving l-glutamyl residues from pteridine oligoglutamates; used in certain antitumour treatments. Synonym: carboxypeptidase G, conjugase, gamma-glutamate (glutamate gamma-) carboxypeptidase. (05 Mar 2000) |
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| gamma motor neurons | The reflex arc consisting of small anterior horn cells and neuroma, their small fibres projecting to the intrafusal bundle producing its contraction, which initiates the afferent impulses that pass through the posterior root to the anterior horn cells, inducing a stretch reflex. Synonym: gamma motor neurons, gamma motor system, Granit's loop. (05 Mar 2000) |
| motor neurons, gamma | Motor neurons which activate the contractile regions of intrafusal muscle fibres, thus adjusting the sensitivity of the muscle spindles to stretch. Gamma motor neurons may be "static" or "dynamic" according to which aspect of responsiveness (or which fibre types) they regulate. The alpha and gamma motor neurons are often activated together (alpha gamma coactivation) which allows the spindles to contribute to the control of movement trajectories despite changes in muscle length. (12 Dec 1998) |
| motor system disease | <disease> Degenerative disease of unknown cause that affects predominantly motor neurons of spinal cord, cranial nerve nuclei and motor cortex. There is speculation that deficiency in ciliary neurotrophic factor may be involved. (18 Nov 1997) |
| extrapyramidal motor system | Literally: all of the brain structures affecting bodily (somatic) movement, excluding the motor neurons, the motor cortex, and the pyramidal (corticobulbar and corticospinal) tract. Despite its very wide literal connotation, the term is commonly used to denote in particular the striate body (basal ganglia), its associated structures (substantia nigra; subthalamic nucleus), and its descending connections with the midbrain. (05 Mar 2000) |
| extrapyramidal motor system disease | A general term for a number of disorders caused by abnormalities of the basal ganglia or certain brain stem or thalamic nuclei; characterised by motor deficits, loss of postural reflexes, bradykinesia, tremor, rigidity, and various involuntary movements. Synonym: extrapyramidal motor system disease. (05 Mar 2000) |
| bis-gamma-glutamylcystine reductase | <enzyme> From halobacterium halobium; specific for NADPH Registry number: EC 1.6.4.- Synonym: bis-ggc reductase (26 Jun 1999) |
| gamma | <physics> Third letter in the Greek alphabet, variable used for a number of things in physics, in plasma physics gamma is often used as the variable for growth rates of instabilities. (09 Oct 1997) |
| gamma-Abu | gamma-aminobutyric acid |
| gamma alcoholism | Jellinek's term for a severe stage of alcoholism characterised by a progression from psychological to physiological dependence upon alcohol, including tissue dependence and withdrawal symptoms, with loss of control over alcohol intake and destructive effects on interpersonal relationships. (05 Mar 2000) |
| gamma aminobutyric acid | <biochemistry> An important amino acid which functions as the most prevalent inhibitory neurotransmitter in the central nervous system. Gamma aminobutyric acid works in partnership with a derivative of Vitamin B-6, pyridoxine, to cross from the axons to the dendrites through the synaptic cleft, in response to an electrical signal in the neuron and inhibits message transmission. This helps control the nerve cells from firing too fast, which would overload the system. The action of gamma aminobutyric acid decreases epileptic seizures and muscle spasms by inhibiting electrical signals in this manner. Studies have shown that the site of action in the brain of benzodiazepams, including Valium, is directly coupled to the brain receptor for gamma aminobutyric acid. Acronym: GABA (05 Jan 1998) |
| gamma aminobutyric acid receptor | <physiology> Ligand gated chloride ion channel forming receptor opened by gamma aminobutyric acid. Two distinct types: A and B. A receptor: One of a family of neurotransmitter receptors with fast intrinsic ion channels that includes the glycine receptor and the nicotinic acetylcholine receptor. Distinct from another major receptor family, the muscarininc acetylcholine receptor and rhodopsin, with no intrinsic ion channel. The A receptor is specifically blocked by bicuculline. It consists of two pairs of protein chains forming an A2B2 complex, the A chains bind benzodiazepine and the B chains bind GABA. The 4 subunits are thought to form a tight group with the chloride channel in the middle. There is considerable similarity between the amino acid sequences of the receptor subunits and those of the nicotinic acetylcholine receptor suggesting that both receptors are derived from some evolutionary ancestor. See: amino acid receptor superfamily. B receptor: Brain receptor (80 kD) for the inhibitory neurotransmitter gamma amino butyric acid. Differs from the A receptor both in agonist specificity (baclofen is a specific agonist) and its effects on cells. It modulates intracellular calcium levels through a Go mediated effect on N type calcium channels and also lowers intracellular cAMP levels by an effect on adenylyl cyclase, thereby reducing the secretion of catecholamines. (05 Jan 1998) |
| gamma-amylase | A hydrolase removing terminal alpha-1,4-linked d-glucose residues from nonreducing ends of chains, with release of beta-d-glucose. Synonym: acid maltase, amyloglucosidase, gamma-amylase, glucoamylase. (05 Mar 2000) |
| gamma angle | <ophthalmology> The angle formed between a line joining the fixation point to the centre of the eye and the optic axis. (05 Mar 2000) |
| gamma-anticollagenase | <chemical> Serum protease inhibitor (26 Jun 1999) |