Accessing product category attributes in Mage_Catalog_Block_Navigation

Question

I am completely new to Magento and have just now installed Magento Community Edition 1.8.1.0. I have created a few product categories from the admin console. I would like to customize the top menu based on some attributes of individual product categories. I have figured out that the changes I need to make will be in a class that overrides Mage_Catalog_Block_Navigation.

The method _renderCategoryMenuItemHtml in this class is invoked with a category. Specifically, I need Is Anchor, Description and Page Title attributes of the category in this method besides the usual ID, name and URL. I can see that the category passed to this method is an instance of Varien_Data_Tree_Node but this instance does not contain the three attributes I need.

I know that I can use the category ID available inside this method to run queries on the database to get the information I need, but I do not want to do this due to performance reasons. I am assuming that there is some code that is fetching category information from the database and is setting that information in Varien_Data_Tree_Node instances. I would like to enhance that code to include the additional attributes I need. However, I have been unable to find that code even after spending 2 days on this.

Can someone point me to the code where I can set the additional attributes in the Varien_Data_Tree_Node instance? Any alternate way of getting category attributes in the Navigation Block would also be helpful, as long as they do not affect performance.