blood pressure and heart rate

How does captopril reduces blood pressure, and what will happen to my heart rate if i dive into a cold lake on a hot summer's day?

Captopril is an angiotensin converting enzyme(ACE) inhibitor. ACE is an enzyme in the body which is important for the formation of angiotensin II. Angiotensin II causes constriction of arteries in the body, thereby elevating blood pressure. ACE inhibitors such as captopril lower blood pressure by inhibiting the formation of angiotensin II, thus relaxing the arteries. Relaxing the arteries not only lowers blood pressure, but also improves the pumping efficiency of a failing heart and improves cardiac output in patients with heart failiuer.

As per your second Q,
How cold is the water?
Usualy after short time in cold water The heart rate can increase by 50% and blood pressure increase can increase to 175/90.

thanks admin. i also have anotheR qn.
QN1.is vital capacity affected by the your position i.e whether you are standing or lying down. what is the difference and why.
QN2. when your left side of the thorax is knifed, why does only one lung collapse?