Depending on the type of receptor, the effect on the postsynaptic cell may be excitatory, inhibitory, or modulatory in more complex ways. In some colonial eukaryotes such as Obelia electrical signals do propagate not only through neural nets, but also through epithelial cells in the shared digestive system of the colony.
The relaxing effect of the exogenously applied LWamide peptide is also observed in epithelial hydra. These provide some of the background and context for a Royal Society meeting to discuss new data and concepts that might achieve insights into the origin and evolution of brains and nervous systems.
In radially symmetric animals such as the jellyfish and hydra, the nervous system consists of a diffuse network of isolated cells.
Neurons and synapses Figure 4: Major elements in synaptic transmission. Rushforth and Hofman have reported that during capture of prey the tentacle contraction is limited to the portion on the proximal side that is the side closer to the mouth A large number of RFamide peptides and their encoding genes have been identified on bilaterians; C.
Bilateria Figure 2: Nervous system of a generic bilaterian animal, in the form of a nerve cord with segmental enlargements, and a "brain" at the front. In the insect nervous system, the brain is anatomically divided into the protocerebrum, deutocerebrum, and tritocerebrum.
Neurons are generated from a special set of ectodermal precursor cells, which also serve as precursors for every other ectodermal cell type.
White matter includes all of the body's nerves, and much of the interior of the brain and spinal cord.
On the limbs, the layout of the innervation pattern is complex, but on the trunk it gives rise to a series of narrow bands. When neurons that are intrinsically rhythmic are connected to each other by excitatory or inhibitory synapses, the resulting networks are capable of a wide variety of dynamical behaviors, including attractor dynamicsperiodicity, and even chaos.