课程描述展开后应显示“收起描述信息”

app/views/layouts/base_courses.html.erb

@@ -157,9 +157,9 @@
           </div>
         </div>
         <div class="lg-foot" id="lg-foot" onclick="show_more_msg();">
-          <%= l(:label_expend_information)%>
+          <label id="expend_more_information"  value="show_more"><%= l(:label_expend_information)%></label>
           <span class="g-arr-down">
-            <img src="/images/jiantou.jpg" width="12" height="6" />
+            <img id="arrow" src="/images/jiantou.jpg" width="12" height="6" />
           </span>
         </div>
       </div><!--项目简介 end-->

public/javascripts/course.js

@@ -475,6 +475,19 @@ function submitMemberSerch(content)
 function show_more_msg()
 {
     $("#course_description").toggleClass("course_description_none");
+    var information = $("#expend_more_information");
+    var arrow = $("#arrow");
+    var val = information.attr("value");
+    if (val == "show_more") {
+        $("#expend_more_information").text("收起描述信息");
+        information.attr("value", "hide_more");
+        arrow.attr("src", "/images/jiantouup.jpg")
+    }
+    else {
+        $("#expend_more_information").text("展开更多信息");
+        information.attr("value", "show_more");
+        arrow.attr("src", "/images/jiantou.jpg")
+    }
 }
 //作业描述显示更多信息
 function news_show_more_des(id)