ELI5 Screaming in Pain - Why do we scream to relieve physical pain?

Why does screaming relieve physical pain? What is going on in the brain when we scream? Plus a bonus question: why do some tennis players grunt when they hit the ball?   ... We explain like i'm five!   Thank you to the r/explainlikeimfive community, and specifically the following reddit users whose questions and responses formed the basis of this conversation: needsugar_daddy, tacodelmorte, shamanicrabbit, 2as_ron87, alphawhiskeytangofu, jazzman23uk & madjohnfinn   To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Join us on Facebook: https://www.facebook.com/eli5ThePodcast/  or send us an e-mail: [email protected] ... we love hearing from you!