Topic summary
Hemichordates
Extracted from the Wikipedia article Hemichordate.
Nervous system
Hemichordates lack complex sense organs but possess photoreceptor cells, such as pigmented eyespots at the apical ganglion, and chemoreceptive pre-oral organs. No evidence of neuromuscular junctions suggests that movement of the organism is regulated by the action of neurotransmitters that are released in the muscular tissues.