The AV node receives the impulse from the internodal pathways, delays it by approximately 0.09 seconds and the impulse passes through the AV bundle which delays it for a further 0.04 seconds. The AV node and bundle is able to achieve this delay by slowing the conduction of the electrical impulse. The gap junctions between successive cells of the AV node and bundle fibers are fewer which therefore increases the resistance to the impulse.
There are now reblooming iris available that rebloom in the fall. The rebloomers can be divided in the same way as the one-time bloomers. The best time to plant or transplant iris is after flowering through August. Iris are one of the few perennials to transplant during the hottest part of the year. Established plantings of iris should be divided every 3-4 years or whenever the clump becomes crowded or when flowering decreases.
Transplanting iris that are crowded is easy to do. First, the plants must be dug up, and soil washed off with a hose. The rhizomes should be divided in a way that each section has a fan of stems sprouting out, and a good amount of healthy roots.fter planting iris in either bulb or rhizome form, the plants should be watered. The soil must be well draining, as the bulb and rhizome are both very susceptible to rot. The plants should also be in an area of full direct sunlight. If some shade is provided, the blooms will not be as large or last as long of a time.