Evolution of nervous systems

evolution
The evolution of nervous systems dates back to the first development of nervous systems in animals (or metazoans).wikipedia
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Evolutionary neuroscience

Evolutionary Neurobiologycomparative neuroanatomyevolutionary
Evolutionary neuroscience is the scientific study of the evolution of nervous systems.

Paleoneurobiology

paleoneurologypaleoneurologistpaleoneurological
Brain evolution can be studied using endocasts, a branch of neurology and paleontology called paleoneurology.

Nervous system

neuralnervousneurogenic
The evolution of nervous systems dates back to the first development of nervous systems in animals (or metazoans).

Animal

Animaliaanimalsmetazoa
The evolution of nervous systems dates back to the first development of nervous systems in animals (or metazoans).

Eukaryote

Eukaryotaeukaryoticeukaryotes
Neurons developed as specialized electrical signaling cells in multicellular animals, adapting the mechanism of action potentials present in motile single-celled and colonial eukaryotes.

Nerve net

nerve ringnerve nets,nerve network
Simple nerve nets seen in animals like Cnidaria (jellyfish) evolved first, consisted of polymodal neurons which serve a dual purpose in motor and sensory functions.

Cnidaria

cnidariancnidarianscnidarian venoms
Simple nerve nets seen in animals like Cnidaria (jellyfish) evolved first, consisted of polymodal neurons which serve a dual purpose in motor and sensory functions. Jellyfish, comb jellies, and related animals have diffuse nerve nets rather than a central nervous system.

Evolution

evolvedtheory of evolutionevolutionary
Simple nerve nets seen in animals like Cnidaria (jellyfish) evolved first, consisted of polymodal neurons which serve a dual purpose in motor and sensory functions.

Ventral nerve cord

nerve cordnerve cords ladder nerve system
Bilateral animals – ventral nerve cords in invertebrates and dorsal nerve cords supported by a notochord in chordates-- evolved with a central nervous system that was around a central region, a process known as cephalization.

Dorsal nerve cord

nerve corddorsaldorsal hollow nerve cord
Bilateral animals – ventral nerve cords in invertebrates and dorsal nerve cords supported by a notochord in chordates-- evolved with a central nervous system that was around a central region, a process known as cephalization.

Notochord

notocordembryonic notochord cells
Bilateral animals – ventral nerve cords in invertebrates and dorsal nerve cords supported by a notochord in chordates-- evolved with a central nervous system that was around a central region, a process known as cephalization.

Chordate

Chordatachordatesnerve cord
Bilateral animals – ventral nerve cords in invertebrates and dorsal nerve cords supported by a notochord in chordates-- evolved with a central nervous system that was around a central region, a process known as cephalization.

Cephalization

cephalisationforming a headcephalic
Bilateral animals – ventral nerve cords in invertebrates and dorsal nerve cords supported by a notochord in chordates-- evolved with a central nervous system that was around a central region, a process known as cephalization.

Action potential

action potentialsnerve impulsenerve impulses
Neurons developed as specialized electrical signaling cells in multicellular animals, adapting the mechanism of action potentials present in motile single-celled and colonial eukaryotes.

Multicellular organism

multicellularmulticellular organismsmulticellularity
These use calcium rather than sodium action potentials, but the mechanism was probably adapted into neural electrical signaling in multicellular animals.

Obelia

hydroidsObelia geniculataSea fur
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.

Epithelium

epithelialepithelial cellsepithelial cell
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.

Sponge

spongessea spongePorifera
Sponges have no cells connected to each other by synaptic junctions, that is, no neurons, and therefore no nervous system.

Synapse

synapsessynapticpresynaptic
Sponges have no cells connected to each other by synaptic junctions, that is, no neurons, and therefore no nervous system.

Homology (biology)

homologoushomologyhomolog
They do, however, have homologs of many genes that play key roles in synaptic function.

Postsynaptic density

post-synaptic densitypostsynapticpostsynaptic densities
Recent studies have shown that sponge cells express a group of proteins that cluster together to form a structure resembling a postsynaptic density (the signal-receiving part of a synapse).

Ctenophora

ctenophorecomb jelliesctenophores
Jellyfish, comb jellies, and related animals have diffuse nerve nets rather than a central nervous system.

Ganglion

gangliaganglion cellspreganglionic neurons
In some cases groups of intermediate neurons are clustered into discrete ganglia.

Radiata

coelenteratecoelenteratesradiates
The development of the nervous system in radiata is relatively unstructured.

Endoderm

endodermalEntodermdefinitive endoderm
Unlike bilaterians, radiata only have two primordial cell layers, endoderm and ectoderm.