In this task, you are given a question and answer for that. The answer will fill in the blank or will complete the unfinished question. Your task is to provide an explanation based on the given question or fill-in-the-blank statement, and answer.
Q: Question: Sandra was suddenly scared and her adrenal glands secreted adrenaline to prepare her fight or flight response, which caused her heart rate to 
 Answer: increase
A: 
This causes the delivery of less oxygen to the cells, and this stimulates the heart rate via adrenalin, so that pulse rate increases in an effort to deliver enough oxygen to cells.