Blood pressure over 140/100 would be considered high in any age. You should see a doctor if your blood pressure is higher than that (in either number). If you get to the point of having a splitting headache or feeling dizzy, it's a good idea to see a doctor immediately.
Usually it would cause low blood pressure from dehydration and hypovolemia.
Blood pressure would decrease
The kidneys retain salt when the blood pressure is low. This keeps fluid in the body, thus maintaining the blood pressure. The kidneys cause vasoconstriction in the body when the blood pressure is low. This raises the blood pressure.
high
I would say yes. If you got hit in the head there may be an internal bleeding whereas the blood may also clot. There is no spac to get that bad blood out so as the blood increases there is pressure placed on that side or that area where you got the hit causing your heart pressure to rise then leading to High Blood Pressure.
There are several things that can cause this. Hypovolemic shock comes to mind. This means you may have too little blood flowing in your body. This, by its self, will cause your blood pressure to fall. When your body recognizes that the blood pressure is too low (because your tissues will not be being perfused adequately), your heart rate will increase to attempt to compensate for the low blood pressure.
Hypovolaemia is the medical name for "low volume". It refers to the circulatory system. You can be very dehydrated because of not drinking fluids and your blood volume would be decreased but this would cause you to have a low blood pressure. You would feel faint and perhaps see stars when you stand from the sitting/lying position. Blood volume can also be low due to blood loss following serious trauma, a cut, or because of a perforated stomach ulcer for example. This would also cause your blood pressure to fall. As a hospital patient you would probably be given an infusion of saline if you are dehydrated of a blood transfusion if you have has blood loss. In either case, if these flow in to your system too fast this may cause you blood pressure to be high. You could also have other complications loke breathlessness. Hope this helps.
I would be worried about cardiovascular disease or kidney failure.
Blood pressure would decrease
Blood pressure would decrease
Blood pressure would increase
Blood pressure would increase