Final answer:
Adrenaline released into the bloodstream increases heart and breathing rates, directs more oxygen and blood to vital organs, and prepares the body for a 'fight or flight' response. These changes are facilitated by the autonomic nervous system and the endocrine system to help react to stress.
Step-by-step explanation:
The body's response to stress involves the quick release of hormones by the endocrine system, particularly adrenaline (also known as epinephrine) from the adrenal glands. When adrenaline is released into your bloodstream, it causes your heart rate to increase and your breathing rate to accelerate, preparing your body for a 'fight or flight' reaction. Additionally, adrenaline triggers the conversion of glycogen to glucose in the liver and skeletal muscles, increases oxygen availability by dilating the bronchioles, and redirects blood flow from non-critical to critical organs, thus enhancing your body's capacity to react to stress.
Other physiological changes during this response include activation of sweat glands, dilation of pupils, and increase in blood pressure. These changes ensure that your body is ready to face imminent threats by improving transport of oxygen to the brain and muscles. The autonomic nervous system plays a crucial role in triggering the adrenal glands to secrete adrenaline swiftly in response to stress, thereby enabling the body to respond rapidly to environmental changes that require immediate action.