[jQuery] Accordion Header Image Replacement

[jQuery] Accordion Header Image Replacement


I have a simple accordion set up with the code below, but I want to be
able to change the header's background image from an up arrow state to
down arrow state and back automatically. Any ideas on where to go from
here?
$(document).ready(function() {
$('div.acc> div').hide();
     $('div.acc> h1').click(function() {
        var $nextDiv = $(this).next();
        var $visibleSiblings = $nextDiv.siblings('div:visible');
        if ($visibleSiblings.length ) {
         $visibleSiblings.slideUp('slow', function() {
            $nextDiv.slideToggle('slow');
         });
        } else {
         $nextDiv.slideToggle('slow');
        }
     });
});
-------------------------------------
<div class="acc">
    <h1>Test</h1>
    <div>Hidden Text</div>
    <h1>Test</h1>
    <div>Hidden Text</div>
</div>