I've been wondering this for a while now Magicka is just a reserve of a creatures supernatural power, how does a person/mer get effected by using their magick pool like if they cast a spell that drained all their magicka would they feel fatigue?
When I think about it, it seems like using magic would have some sort of effect on a creatures physiology since soul quality (quality in trapping like lesser,greater ect) is usually tied in with how magical a creature is.

I don't see minotaur lords as very magical to be honest, and they have grand souls. I think that the level of a soul is based on how powerful the creature is in question. I couldn't really give you an answer as to whether magicka drain has any effects on a person or not. Maybe one of the more studied lore buffs can assist you.

Magicka actually comes from Aetherius, not a creature's internal reserves.

Well I just meant the soul trapping thing in a general way it seems roughly that the more magic a creature is the better the quality soul you can trap, and the better soul to trap usually belongs to stronger creatures.
I was thinking along those lines because being stronger could be from having an affinity, creation, or link to magic effecting it's physiology. Not just strength wise but also life spans and what not.

The internal reserves was a description from Morrowind. By reserve I just mean like a pool, potential limit like how many points they can spend like say they got 100 magicka total to use at any given point if it's fully charged.

And yet people have differing levels of magicka available to them.

There must be some kind of physiological effect, even if it's just as minor as the more magicka you have, the more aware of it you are (maybe you get static shocks occasionally when you touch things, or something).

Well in the books the Penitus Oculatus agent has a passive magical ability that allows him to see "ghosts". If he depleted his magicka he probably wouldnt be able to see them anymore. I think it has to do with your passive connection to the world around you.

I know an Altmer's inherent magical abilities allow them to sense the pain and suffering of the Daedric essence inside of Daedric armor and weapons. Anybody who has enough magicka in them probably can.

I don't think soul size and magic have much to do with each other. Tolfdir (I think) mentiones being able to feel "resonances" from objects of vast magical power, and wizards are known "by reputation" to live longer than non-mages, so plainly long use of magicka does have some physical and mental effect on you. We just lack the information at this time to fully catalogue the effects.

Young elven children and some human children often hurt themselves practicing magic early kn.

One master Telvanni's talent was found when, at the age of two, she conjured a fire spell strong enough to burn off her hand.

Really, what's that from? It actually sounds like a pretty evocative scene from a dark fantasy novel, but I don't remember it. Source?

From both the Mystery of Talara series and http://www.uesp.net/wiki/Morrowind:A_Hypothetical_Treachery that magicka drain leaves you vulnerable, but not actually weakened.

A quick thought I jotted down.

Yes, that's true. But having depleted magicka wouldn't weaken you, it would just make you feel mundane.

Now, the act of using magicka would probably strain the body and mind.