Pressure points are not scientific anatomical locations. They are areas of the body that are particularly susceptible to incapacitating pain or injury. Some seem obvious and are therefore usually well guarded. While more obscure locations can be a total surprise to the attacker, which is always a bonus.
Different people react differently to pain stimulus. If the attacker is using alcohol or drugs their pain sensitivity can be dulled, also. So it is hard to judge what kind of response you will get. Therefore it is appropriate to use as much force as you can muster when you deal with these areas. Although it isn’t necessary to injury the assailant, sometimes all that’s needed is enough to convince him that a spirited defense will be made and you will not be a passive victim.
Sometimes all you need is to inflict adequate surprise and/or pain to cause him to lose his grip on you so you can escape. Sometimes causing an injury is warranted to keep him from chasing you.
Let me dispel a couple myth for you. There is no secret spot on the body that, when pressured will cause instant unconsciousness. Apparently that only happens on Star Trek. Secondly, you cannot instantly kill someone by driving their nose up into their brain. You will hurt them, but it does not cause instantaneous death.
Some of the pressure points are:
This is by no means a complete list, sometimes it just depends on what’s available within reach.
Parts of your body that you can strike with:
Fingers are good for eye gouging, and pinching. The back of your head can head butt (so can the front, but less likely to cause damage to you). Elbows are a favorite of mine, they can be used forward or backwards; they can be reinforced by clutching the associated fist with the opposite hand (assisted elbow strike).
Awareness of pressure points should be an integral part of any self defense plan.