Glossary of plant morphology others may form a tight spiral, or whorl, around the flower stem. First, at the base, are those non-reproductive structures involved in protecting the flower when it is still a bud, the sepals, then are those parts that play a role in attracting pollinators and are typically coloured, the petals, which together with the sepals make up the perianth (perigon, perigonium). If the perianth is differentiated, the outer whorl of sepals forms the calyx, and the inner whorl of petals, the corolla. If the perianth is not differentiated into sepals and petals, they are collectively known as tepals. In some
Calyx of Held The first is that in the second week of development, myelination of the VCN axons in the MNTB increases. This prominent growth in myelin corresponds to the chronological development of the signaling circuit and adaptation of the calyx. The second ultrastructural change involves the principal neurons of the MNTBs, whose cell bodies and nuclei increase in surface area due to enlargement. This is a direct result of individual, larger postsynaptic densities breaking up into smaller, multiple densities. Potassium channels are vital in conducting the presynaptic action potential. The calyx contains several types of potassium channels, each differing in location and