I would like to change the default arrow head style in quiver plot. How can I change it?
You can start here:
http://www.mathworks.com/help/matlab/ref/quiver.html
and then you can look for the available properties of quiver here:
http://www.mathworks.com/help/matlab/ref/quivergroupproperties.html
For example, the property MaxHeadSize allows to change the size of the arrow-heads.
EDIT: More information in this link: Arrow properties
Read at bottom, where says
You can select an annotation and then choose Show M-code to obtain a code snippet that you can insert in a function or script to reproduce the annotation.