The simple answer is like Christian Hupfer implicitly writes: Change the \chapter{RAA...} to \section{RAA...}.
Your MNWE will be:
\documentclass{article}
\usepackage{pdfpages}
\begin{document}
\section{RAA renal hormones} \label{06222014204556}
\includepdf[pages={-}]{06222014204556.pdf}
\end{document}
If you want more easy options, I will suggest switching to the KomaScript bundle. Then you can easily switch between small, medium and big headings, see page 86-88 in the manual.
\documentclass[headings=big,% or normal or small
fontsize=12pt]% or 10pt or 11pt - 12pt give huge headings
{scrartcl}
\usepackage{pdfpages}
\begin{document}
\section{RAA renal hormones} \label{06222014204556}
\includepdf[pages={-}]{06222014204556.pdf}
\end{document}
If you really want to add the word Chapter in front of the section number, and have the section title on its own line, i.e.
Chapter 1
RAA renal hormones
(text on new page)
you have to redefine the section command. That is an advance exercise.
articledoesn't provide the command\chapter: See Regarding thebook,report, andarticledocument classes: what are the main differences? – Marco Daniel Jun 29 '14 at 07:51RAA renal hormones? Apart from the fact what Marco Daniel already mentioned, it is just\section{\Huge RAA renal hormones}. Inbook.cls,\hugeand\Hugeprovide the same font size... – Jun 29 '14 at 07:52\includepdfcommand for a file not available to users here. – Jun 29 '14 at 07:55