<Li> Neural signalling is an all - or - nothing (digital) action, whereas hormonal signalling is an action that can be continuously variable as dependent upon hormone concentration . </Li> <P> Hormone transport and the involvement of binding proteins is an essential aspect when considering the function of hormones . There are several benefits with the formation of a complex with a binding protein: the effective half - life of the bound hormone is increased; a reservoir of bound hormones is created, which evens the variations in concentration of unbound hormones (bound hormones will replace the unbound hormones when these are eliminated). </P> <P> The discovery of hormones and endocrine signaling occurred during studies of how the digestive system regulates its activities, as explained at Secretin § Discovery . </P>

What molecule forms the internal skeleton from which all steroid hormones are derived