Which one topic or concept has been the most difficult for you so far in this course (The endocrine system, The circulatory system blood or heart)?  What specifically is "muddy" or not quite clear about that topic?  Please be as specific as possible in identifying the topic.  For example, "I can't figure out how ADH affects blood viscosity."  After identifying the topic, try to elaborate on what you know thus far about it and/or ask specific questions(s) about it.  Please make the subject of your discussion the title to make it easier for classmates to identify areas that they may be able to share insights on.

Your response should be yours i.e. do not copy/paste & do not type what you find in a book.  Write your response in your own words. 150 words