To answer your question on physical causes of hypertension:
Many people who have known risk factors get high blood pressure for which the exact cause cannot be determined. This is essential hypertension and amounts to more than 90% of diagnosed cases. You can easily find out what the risk factors for developing high blood pressure are and how many apply to you.
Some of the physical factors contributing or resulting in this disease are:
(I am sure there are many more I have not mentioned here)
genetics - if it's in your family's history, chances are you'll get it, too
aging (results in gradual blood vessel constriction)
certain medicines and supplements
use of illegal drugs
Certain medical conditions result in hypertension. This is called secondary hypertension. Quite often, it's difficult to pinpoint the exact cause. For instance, hypertension causes kidney disease, while kidney disease causes hypertension. How to decide which came first? (The jury is still out on mine) Some of the physical conditions causing hypertension are:
adrenal gland tumors
thyroid gland disorders
I hope this helps.