Simply put, a neuron has two ends: the dendrite and the axon. Dendrites are the branches surrounding the cell nucleus (dendrite literally means "tree"). On the surface of the dendrite are synaptic receptors. Through these receptors, the dendrite receives information from the axons of other neurons. The dendrites transmit these stimuli to the nucleus, while the axons conduct stimuli away from the nucleus. The larger the dendrite surface area, the more information from other neurons the dendrite can receive.
Dendrites can also contain spines. These are small nodes connected to the surface of the dendrite by a narrow tube. Synapses are also located on these dendritic spines.
Axons and dendrites remain subject to constant change. This process is driven by experiences and learning. The more stimuli an organism receives, the more dendrites sprout. A rat living in an enriched environment, for example in a cage with lots of toys and variety, will develop more dendrites than a rat living in a bare cage. This is because in the enriched environment, the rat receives more stimuli and is stimulated to be active. Therefore, the growth of dendrites and axons in rats is associated with improved learning capacity. In humans, however, these effects are nonexistent or minimal. Thus, it is not the case that the brain is a muscle that can be trained, as is often thought. "Brain training" does improve performance on the task being trained (for example, a particular memory task), but has little or no effect on other skills or overall intellectual functioning.
Author: Bart Aben (translated by Thomas von Rein)