tiger7

Hi all, I am studying for a physiology exam, and in my notes I have written that "the increased extracellular ionic concentration that osteoblasts form support nucleation and growth." I understand everything in this except for the nucleation part. I've been looking into it and I believe it has something to do with the formation of hydroxyapatite, but I have no idea how. If anyone has any insight on this it would be greatly appreciated. Thank you in advance.

I'm doing some homework for physiology and this is one of the questions: "Striking the ulnar nerve in your elbow against a hard surface (sometimes called “hitting your funny bone”) initiates action potentials in the middle of sensory and motor axons traveling in a nerve. In which direction will those action potentials propagate? Explain." So I have two questions: 1) I said that it will travel in both directions since there is no absolute refractory period to prevent it from traveling back towards the axon hillock/soma. Is that correct? 2) If that is the case, what would happen when the action potential that is moving backwards reaches the soma? Does it actually cause a sensation of any sort?

First post here, mainly because I've never had this much trouble figuring out an answer. Here's what I'm stuck on: What is a taxa that is either a taxonomic or biogeographic relict but not both? I'm pretty sure this is going to be part of an essay question on my final later this week, and I've been stumped for a few days now. I know examples that are considered both, and there are some that would technically work, but we cannot use (ginkgo, humans). Any tips on where to look, or certain things to look for would be appreciated. Thanks in advance.