In circle $J$, $HO$ and $HN$ are tangent to the circle at $O$ and $N$. Find the number of degrees in the sum of $m\angle J$ and $m\angle H$. [asy]
size(150);
import graph;
pair J = (0,0), H = (6,0), O, N;
path circ = Circle(J,3);
pair M = midpoint(J--H);
path secCirc = Circle(M,3);
pair[] tangentPoints = intersectionpoints(circ,secCirc);
O = tangentPoints[0]; N = tangentPoints[1];
draw(J--N--H--O--cycle);
draw(circ);
label("$H$",H,E);
label("$J$",J,W);
label("$N$",N,S);
label("$O$",O,NE);
[/asy]
Since $\overline{OH}$ and $\overline{NH}$ are tangent to radii of the circle at $O$ and $N$, we have $\angle O =\angle N = 90^\circ$.  The sum of the measures of the interior angles of quadrilateral $JOHN$ is $360^\circ$, so $\angle J + \angle H = 360^\circ - \angle O - \angle N = \boxed{180^\circ}$.