\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[russian]{babel}
\usepackage{tikz}
\usetikzlibrary{shapes}
\usetikzlibrary{arrows,positioning}
\begin{document}

\begin{figure}
\centering
\begin{tikzpicture}[node distance=1cm, auto] 
\tikzset{
    main_node/.style={ellipse, ,draw=black, top color=white, bottom color=yellow!50,thick, inner sep=1em, minimum size=3em, text centered, double},
    mynode/.style={rectangle,rounded corners,draw=black, top color=white, bottom color=yellow!50,very thick, inner sep=1em, minimum size=3em, text centered},
    myarrow/.style={draw},
}

\node[main_node] (top) {Государственная власть}; 
\node[mynode, below=2cm of top] (center) {Судебная};
\node[mynode, left=of center] (left) {Законодательная};
\node[mynode, right=of center] (right) {Исполнительная};

\draw[myarrow] (top.south) -- (center.north);   
\draw[myarrow] (top.south) -- ++(0,-1) -|  (left.north);   
\draw[myarrow] (top.south) -- ++(0,-1) -|  (right.north);

\end{tikzpicture}
\end{figure}

\end{document}

\documentclass{minimal}
\usepackage{tikz}
\usepackage[utf8]{inputenc}
\usepackage[russian]{babel}
\usetikzlibrary{backgrounds,calc,positioning,shapes,shapes.callouts}

\begin{document}
  \begin{tikzpicture}[%
    shorten >=3pt,
    shorten <=3pt,
    node distance=5cm,
    note/.style={draw,fill=white,rectangle callout,minimum width=10em,minimum height=4ex},
    content/.style={draw,fill=white,ellipse,minimum width=10em,minimum height=4ex}
  ]
    \node[content]                                   (a) {''Пойдем спать''};
    \node[content]                                   (b) [right of=a]                     {сказал Вася};
    \node[note,callout relative pointer={(0,-0.75)}] (c) [node distance=1.5cm,above of=a] {Прямая речь\strut};
    \node[note,callout relative pointer={(0,-0.75)}] (d) [right of=c]                     {Слова автора\strut};

    \path (a) edge (b);
    \begin{scope}[on background layer]
      \draw[fill=gray!25] ($(c.north west)+(-20pt,15pt)$) rectangle ($(d.south east)+(20pt,-65pt)$);
      \draw[fill=gray!10] ($(a.south west)+(-20pt,-10pt)$) rectangle ($(b.north east)+(20pt,10pt)$);
    \end{scope}
  \end{tikzpicture}
\end{document}