\documentclass[tikz,border=5pt]{standalone}
\usepackage[utf8x]{inputenc}

\begin{document}
    \begin{tikzpicture}[font=\tiny]
        \tikzstyle{node_style} = [draw=white, very thick, circle, fill=orange]
        \tikzstyle{arrow_style1} = [->, black, line width=1, >=latex]
        \tikzstyle{arrow_style2} = [->, gray, line width=1, >=latex]
        \tikzstyle{arrow_style3} = [->, black, line width=3, >=latex]
        \tikzstyle{edge_style2} = [lightgray, line width=1]
        \tikzstyle{line_style1} = [-, gray, line width=1]


        \node[node_style] (n0) at (2,2) {O};
        \node[node_style] (na) at (2,0) {A};
        \node[node_style] (nb) at (0,2) {B};
        \node[node_style] (nc) at (4,2) {C};
        \node[node_style] (nd) at (2,4) {D};

        \draw[arrow_style1] (na) edge (n0);
        \draw[arrow_style2] (n0) edge (nb);
        \draw[arrow_style2] (n0) edge (nc);
        \draw[arrow_style2] (n0) edge (nd);

        \draw[arrow_style1, dashed, rounded corners] (1.8,0.2) -- (1.8, 1.8) -- (0.2, 1.8);
        \draw[arrow_style1, dashed, rounded corners] (2.2,0.2) -- (2.2, 1.8) -- (3.8, 1.8);
        \draw[arrow_style1, dashed] (2.1, 0.3) -- (2.1, 3.7);
    \end{tikzpicture}
\end{document}
