Passerina (plant) large enough to cover them. This gives the plants a characteristic plaited or corded appearance. The flowers of some species are borne in terminal spikes, whereas other species bear them in a four-flowered head. Bracts, usually broader than leaves and larger than the flowers, subtend each flower. This is one helpful distinction between specimens of "Passerina" and plants in the genus "Struthiola". The calyx has four sepals, forming a flask-shaped or subcylindrical tube. At the mouth the sepals spread into lobes that are shorter than the tube. There are no petals, but the lobes of the sepals are quite colourfully
Calyx of Held the calyx is not only characteristic, but pragmatic in terms of auditory chronological development. As a synapse, the calyx of Held follows a mechanism similar to other synapses. A thorough description can be found under neurotransmission. Calcium influx for the immature calyx of Held is mediated by N-, P/Q-, and R-type calcium channels; however upon maturation only P/Q-type calcium channels become dominant. Upon calcium influx, the immature calyx of Held is highly reactive due to its small calcium buffer ability – this causes the release of glutamate even at low levels of calcium influx. Within the terminal, as with other