Thanks for the assistance people! Appreciate all your help 
@pi: I hope everything I just read is not in VCE bio haha 
. I understand that there are different nerves for pain, temperature, etc, but this might be a bit too in-depth for VCE, but what is pain? Haha, I know it is caused by the action potential stimulating nerve cells, but i once remember doing a question saying that a specific drug can inhibit pain. This drug obviously blocks the neurtransmitter's receptors on the post synaptic membrane, so the post synaptic cell cannot be stimulated (feel pain?). Can pain be the result of electrical impulse on any cell/tissue? or is it only skin?
Cheers, apologies for the 'all over the place' question.
The take-home VCE bio point is: there are many different types of nerves
Now, an interesting and totally-out-of-the-course question about pain, I'll try and tie in some clinical stuff that you'd know!
I guess if we were to define pain, we'd say it's a subjective unpleasant sensory experience and/or an unpleasant emotional experience. To further the sensory experience, we could say it's associated with actual or potential tissue damage (hence it's a protective thing, it provides warning for more harm, which is the whole point of pain!).
From there, things become a bit more complicated. The receptors that carry the sensation of pain are free nerve endings ({g} in that Nature picture I posted above, right at the end of that table), from that receptor there are two different types of nerves that carry the signal: A-delta (these carry signals relatively fast, and are hence more involved in sharp, pricking, electric pains) and C fibres (these carry signals slower, and are hence involved in burning, aching, chronic pains). The important thing to realise is that there is always this "double pain sensation" through each of those nerve types. To make this further confusing/interesting, different ion channels are involved in different types of pains, which is why (well, one of the reasons anyway) without looking you can tell the difference between an electric shock and a pin.
Basically the way these receptors ('nociceptive receptors') work is that there is surrounding damage -> inflammatory agents released -> activation of secondary enzymes -> lowers threshold for certain ion channels to open in the nerve (remember it's a free nerve ending!) -> specific signal transmitted. This signal goes up the spine, mainly through something called the 'spinothalamic tract', up to the brain.
Ok, but here's the REALLY interesting part, something that you probably "know", but don't know "why" (or perhaps never given it much thought?). There are other types of nerves, one is called A-beta. If you look at the aforementioned Nature picture, you can see that they are involved in various other sensations. Their role in pain is interesting, they are able to modulate the pain signal via an inhibitory interneuron. Hence, if you rub your toe that you just stubbed, you activate this A-beta pathway, and down-modulate your pain sense! This is a simplification of the famous "gate control theory" and hopefully explains to you why rubbing a painful area can help relieve the pain!
Hopefully that sparked some interest!
Regarding your question on pain medications. This becomes considerably more complicated haha (I know right!?!). There are many types of pain meds, let's go over a couple of the ones you've heard of:
- Morphine ("opiods"): these work by blocking receptors that are present in nerve cells in the CNS, and block the signal that way
- Ibuprofen ("Nurofen"): these work by reducing inflammation, and as above, less inflammation means less activation of secondary enzymes and a higher threshold for the action potential to go through
There are heaps of other types, but hopefully that gives you a simple taste of things!
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