Dictionary of Biological Psychology
(from Latin, rigidus: stiff) This is an everyday term that is used in various scientific contexts. For example, the BASILAR MEMBRANE is often described as being rigid, meaning that it has a certain stiffness that is important to its functions.
Rigidity is a term that has been used also in PSYCHIATRY and CLINICAL PSYCHOLOGY to indicate a PERSONALITY type in which resistance to change is a principal feature. However, in biological psychology, the term rigidity encountered alone usually refers to rigidity of the MUSCLES.
Muscular rigidity appears in several forms in different conditions. These include: CATATONIC RIGIDITY: muscular rigidity present in CATATONIA (and see also SCHIZOPHRENIA); CEREBELLAR RIGIDITY: this follows damage to the VERMIS of the CEREBELLUM and is caused by increased tone in the EXTENSOR MUSCLES; CLASP KNIFE RIGIDITY: is rigidity of the extensor muscles at a joint, leading to a rigid, bent, positioning of a limb; COGWHEEL RIGIDITY: is a condition seen in PARKINSON’S DISEASE—movement of a limb has a jerkiness that appears similar to that of moving a toothed cog one space at a time; DECEREBRATE RIGIDITY: is muscular rigidity that appears following TRANSECTION through the brain at very low levels in the NEURAXIS; LEAD PIPE RIGIDITY: is a form of rigidity, sometimes seen in Parkinson’s disease, in which it seems possible to gradually bend a patient’s limb as if one were bending a soft lead pipe (see also WAXY FLEXIBILITY); and finally, CADAVERIC RIGIDITY—also known as rigor mortis—is the stiffening of the muscles that occurs after death, caused by coagulation of muscle PROTEINS.
This is the complete article, containing 257 words
(approx. 1 page at 300 words per page).
View More Summaries on Rigid
