Abnormal physical or morphological growth, especially of a particular anatomical feature. As a branch of medicine, it combines concepts, knowledge, and techniques from the fields of embryology, clinical genetics and paediatrics. Term first used by David W. Smith (1926-1981) in the 1960s to describe the study of human congenital malformations (i.e., birth defects), particularly those …
Author Archives: Brian Hopkins
Dyskinesia
Abnormal movements most obvious when the patient initiates a movement. When the patient is totally relaxed, usually in the supine position, a full range of motion and decreased muscle tone may be found. Dyskinetic patients are sub-divided into two sub-groups. Hyperkinetic or choreoathetoid children show purposeless, often massive involuntary movements with motor overflow (i.e., the …
Dynamics
Broadly speaking, the study of the way systems change over time. There are two sorts of dynamics. One is linear (or Newtonian) dynamics in which there is a one-to-one, or proportional, relationship, between input to and output from the state (S) of a system, which can be schematically summarised as follows: The other is non-linear …
Dysgraphia
Sometimes referred to agraphia, it is an impairment in the ability to express thoughts in writing and to write clearly (e.g., mixture of upper and lower case letters, dysfunctional writing grip), regardless of the ability to read. Often associated with other problems in movement coordination (e.g., tying shoelaces), and therefore with apraxia, developmental dyspraxia and …
Dynamical systems approaches
In the wide sense, the use of concepts from the mathematical theory of dynamical systems, based on the principles of self-organization in open systems, to describe how the behavior of complex systems is generated over time, regardless of their material substrate or the particular time scales on which they operate. In the narrow sense, a …
Dynamical parameters
The parameters describing the process of changes within a variable. See Dynamical balance, Dynamical coupling, Dynamical system, Order parameter
Dynamical system
Any system that changes over time. Change can be continuous or discontinuous, and there are mathematical tools available (e.g., catastrophe theory) for distinguishing between these two types of change (and whether discontinuous changes are quantitative or qualitative in nature). The dynamics involved do not necessarily refer only to mechanical forces and masses as in Newtonian …
Dynamical coupling
The parameters describing how the processes of changes within a variable emerge from one variable to another. See Complex system, Developmental emergence, Dynamical balance, Dynamical parameters, Dynamical system, Emergence
Dynamic systems theory (development and evolution)
A theory of biological form, intended to integrate biological evolution and ontogenetic development, that considers the whole organism rather than just genes as in the Modern synthesis. Its main thrust is that gene action takes place within self-organizing morphogenetic fields, which impose constraints on what forms can be generated, both in development and during evolution. …
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Dynamical balance
In a dynamical systems approach, it amounts to flexible rules that alter the relative salience of defined factors such as those that control behavior. See Dynamical parameters, Dynamical system, Rule