Cell typeA cell type is a classification used to identify cells that share morphological or phenotypical features. A multicellular organism may contain cells of a number of widely differing and specialized cell types, such as muscle cells and skin cells, that differ both in appearance and function yet have identical genomic sequences. Cells may have the same genotype, but belong to different cell types due to the differential regulation of the genes they contain.
Axon guidanceAxon guidance (also called axon pathfinding) is a subfield of neural development concerning the process by which neurons send out axons to reach their correct targets. Axons often follow very precise paths in the nervous system, and how they manage to find their way so accurately is an area of ongoing research. Axon growth takes place from a region called the growth cone and reaching the axon target is accomplished with relatively few guidance molecules. Growth cone receptors respond to the guidance cues.
Betz cellBetz cells (also known as pyramidal cells of Betz) are giant pyramidal cells (neurons) located within the fifth layer of the grey matter in the primary motor cortex. These neurons are the largest in the central nervous system, sometimes reaching 100 μm in diameter. Betz cells are upper motor neurons that send their axons down to the spinal cord via the corticospinal tract, where in humans they synapse directly with anterior horn cells, which in turn synapse directly with their target muscles.
AversivesIn psychology, aversives are unpleasant stimuli that induce changes in behavior via negative reinforcement or positive punishment. By applying an aversive immediately before or after a behavior the likelihood of the target behavior occurring in the future is reduced. Aversives can vary from being slightly unpleasant or irritating to physically, psychologically and/or emotionally damaging. It is not the level of unpleasantness or intention that defines something as an aversive, but rather the level of effectiveness the unpleasant event has on changing (decreasing) behavior.
Desensitization (psychology)In psychology, Desensitization is a treatment or process that diminishes emotional responsiveness to a negative, aversive, or positive stimulus after repeated exposure. Desensitization can also occur when an emotional response is repeatedly evoked in situations where the action tendency associated with the emotion proves irrelevant or unnecessary. The process of desensitization was developed by psychologist Mary Cover Jones and is primarily used to assist individuals in unlearning phobias and anxieties.
