It is difficult to participate if you fear ridicule by a team member who is constantly critical of your ideas.
If this problem exists then it should be discussed at a meeting and a strategy put in place to stop the criticism.
Ideally the team leader should ensure that respect is given to everyone's ideas, and that everyone feels that they can give their honest opinions.
DeBono's 'Six Thinking Hats' can be used to good effect here to ensure everyone thinks positively together. The Black Hat can be used initially to get negative thoughts on record (or on a whiteboard) and sometimes this is enough to stop people being actively critical: their concerns have been heard and noted.