What is a physiological effect of stress on the nervous system?

The release of stress hormones, primarily catecholamines like adrenaline and cortisol, triggers various physiological responses in the body, one of which is increased vigilance. This heightened state of awareness is a survival mechanism, allowing an individual to respond more effectively to potential threats in their environment. During periods of stress, the nervous system enters a 'fight or flight' mode, which enhances alertness and prepares the body to react quickly to danger. Increased vigilance can lead to improved focus and attention, which are critical in situations requiring fast decision-making or action.

Other options relate to effects that are generally not associated with the stress response. Decreased heart rate is contrary to the body's typical response to stress, where heart rate typically increases to pump more blood and prepare for a potential physical response. The release of serotonin is often linked to feelings of well-being and relaxation, not stress. Similarly, improved cognitive function is not typically an outcome of stress, as chronic stress can actually impair cognitive functions over time.