Změna zašktrtnutého políčka při změně obrázku

<script> 
obr = 0;
cas = 5000;
function animace(){
obrazky=["img1.jpg","img2.jpg","img3.jpg","img4.jpg","img5.jpg"]
if (obr+1==obrazky.length)obr=1;
else obr++;



obrazek.src = obrazky[obr];
window.setTimeout('animace()',cas);}


function zasrkrtnuti()
{document.getElementById("kolecko").src=obrazky[obr];
            if (obr==0) {
                document.getElementById('kolco1').checked="checked";
                document.getElementById('kolco5').checked="unchecked"} 
                    else {
                        if (obr==1) { 
                        document.getElementById('kolco2').checked="checked"; 
                        document.getElementById('kolco1').checked="unhecked"}
                             else {
                                 if (obr==2) {
                                 document.getElementById('kolco3').checked="checked";
                                document.getElementById('kolco2').checked="unchecked"}
                                     else { 
                                        if (obr==3) {
                                        document.getElementById('kolco4').checked="checked";
                                        document.getElementById('kolco3').checked="unchecked"}
                                            else {
                                                if (obr==4) {
                                                document.getElementById('kolco5').checked="checked";    
                                                document.getElementById('kolco4').checked="unchecked"}}}}}
            obr++;
            if (obr == 5){obr = 0;} }    
    
</script>   

a tady v html:
<form>
        <table class="kolco">
        <strong id="prepinani">Přepínání</strong>:
            <tr>
                <td id="kolco1"> <a onmouseclick="getElementById('kolecko').src='img1.jpg'"><input type="radio"; name="kol"></a><td>
                <td id="kolco2"> <a onmouseclick="getElementById('kolecko').src='img2.jpg'"><input type="radio"; name="kol"></a><td>
                <td id="kolco3"> <a onmouseclick="getElementById('kolecko').src='img3.jpg'"><input type="radio"; name="kol"></a><td>
                <td id="kolco4"> <a onmouseclick="getElementById('kolecko').src='img4.jpg'"><input type="radio"; name="kol"></a><td>
                <td id="kolco5"> <a onmouseclick="getElementById('kolecko').src='img5.jpg'"><input type="radio"; name="kol"></a><td><br>
            </tr>
 
       </table>
    </form>