How do hormones like adrenaline affect stress responses in animals?

Hormones such as adrenaline play a crucial role in the stress responses of animals, particularly through the initiation of the 'fight or flight' response. This response is a physiological reaction that occurs in response to a perceived threat or stressor. When adrenaline is released into the bloodstream, it causes several key changes in the body to prepare the animal to either confront or flee from the danger.

Adrenaline increases heart rate and blood pressure, which enhances blood flow to muscles and critical organs. This prepares the animal for quick and powerful physical activity. Additionally, adrenaline promotes the breakdown of glycogen into glucose, providing a rapid source of energy for immediate use. These changes are designed to enhance survival by enabling the animal to either 'fight' against a threat or 'flight' to safety.

The options that suggest relaxation or a reduction in heart rate do not align with the effects that adrenaline has during a stress response. Instead, the hormone's primary function in this context is to stimulate heightened alertness and readiness for action.