Explain how smoking can increase blood pressure?

There are two main reasons that smoking can increase blood pressure:

1. Cigarette smoke contains nicotine which, once inhaled, can enter the bloodstream and cause the release of adrenaline which increases the heart rate. Increasing the heart rate will also raise the blood pressure. 
   
   
2. Cigarette smoke also contains carbon monoxide which, once inhaled, can enter the bloodstream and bind to haemoglobin. This forms carboxyhaemoglobin, a molecule that oxygen cannot bind to. This results in a decreased concentration of oxygen in the blood which causes a compensatory rise in heart rate which, in turn, raises the blood pressure.