During acute physiological responses to stress, what change occurs to heart rate?

During acute physiological responses to stress, the heart rate increases to improve oxygen delivery. This response is part of the body's fight-or-flight mechanism, which is triggered by the sympathetic nervous system when faced with stressors. When an individual encounters a stressful situation, the body releases hormones like adrenaline (epinephrine) that stimulate the heart to pump faster. This increase in heart rate enhances blood circulation, thus increasing the amount of oxygen delivered to vital organs and muscles.

This physiological adjustment is crucial for preparing the body to respond effectively to threats, whether that means fighting or fleeing. Consequently, elevated heart rate supports increased physical performance and mental alertness in stressful situations, which is why this option is the correct one in the context of acute stress responses.