please help with after and preload

[sissyqt]

Hi, I am a senior nursing student but I am still having a hard time understanding preload and afterload. I understand what they are and the difference b/t them both. I mainly have a problem understanding the affect vasodilators have on them. I know that vasodilators open the blood vessels allowing blood to flow out faster and easier as a result decreasing afterload. I don't understand then how preload is decreased, and CO is decreased. I can't grasp this concept. I can't understand if blood is flowing out more freely why doesn't it return more freely and how is CO decreased please someone explain in lay terms:confused:

[Daytonite, BSN, RN]

preload and afterload are difficult concepts and i, personally, couldn't grasp them in one reading. i don't think anyone can. there have been several previous threads on allnurses about this that you might find helpful:

• https://allnurses.com/forums/f198/preload-afterload-127823.html
  
• https://allnurses.com/forums/f9/student-question-preload-187317.html
  
• https://allnurses.com/forums/f9/preload-afterload-contractility-164426.html
  
• https://allnurses.com/forums/f15/right-ventricular-infarct-question-144835.html
  
• https://allnurses.com/forums/f50/cardiac-preload-afterload-31704.html

there is a whole website devoted to congestive heart failure (http://cvphysiology.com/heart%20failure/hf002.htm) and it has explanations of preload (http://cvphysiology.com/cardiac%20function/cf007.htm) and afterload (http://cvphysiology.com/cardiac%20function/cf008.htm). however, they require reading, cogitation and re-reading in order to fully understand these concepts.