Final answer:
Angiotensin II primarily causes vasoconstriction and increases blood pressure. It stimulates the release of aldosterone and ADH, which both help to retain sodium and water, thus increasing blood volume and pressure. It is generally activated by low blood pressure, not high.
Step-by-step explanation:
The function of Angiotensin II includes causing vasoconstriction, which greatly increases blood pressure. It is not released in response to high blood pressure; rather, its release is usually stimulated by decreases in blood pressure as part of the renin-angiotensin-aldosterone system (RAAS).
Angiotensin II stimulates the adrenal cortex to release aldosterone, which leads to the reabsorption of sodium and consequently water into the blood, thereby increasing blood volume and pressure.
Additionally, Angiotensin II stimulates the release of antidiuretic hormone (ADH), which further helps in water retention, but it is not mainly responsible for increasing urine output. Instead, it works to preserve blood volume during instances like blood loss or dehydration.