The meanings of 神経

Question

I just came across the phrase

どういう神経だ！
What a nerve! (my translation)

in a book translated from English to Japanese. Because it's a translation I'm a little doubtful about whether it's correct/idiomatic.

I can think of three meanings of nerve in English:

1. The biological thingy;
2. The courage to do something;
3. The audacity to do something.

The context of the book means that meaning 3) must be intended. Yet when I look in weblio and kotobank I see nothing that looks like either meaning 2) or 3).

To what extent does 神経 mirror the English meanings?

Answer 1

神経 can appear naturally in non-translated conversations. In a sentence like this, it refers to someone's common-sense judgment. どういう神経だ (or どんな神経をしているんだ) may be said after someone said or did something based on an insane judgement. Courage or audacity is not necessarily relevant, so its meaning may be broader than "What a nerve!" in English. But 神経が図太い is an idiom that means "to have strong nerves" or "fearless", so what it actually refers to depends on the phrase.

Answer 2

Looking at entries in Cambridge online, there are these:

• the courage or confidence necessary to do something difficult, unpleasant, or rude:
• the rudeness to do something that you know will upset other people:

In terms of meaning, nerve and 神経 are rather similar. 神経 is used for daring to do something rude. どういう神経・どんな神経（してる） is more or less equivalent to what a nerve. Rather than 'courage'(勇気) or 'confidence'(自信), it is generally called 厚かましさ.

In terms of translation, my impression is that you need to see it as 'what a nerve' in some way even for 'having the nerve'. For example (from the link above),

She's late for work every day, but she still has the nerve to lecture me about punctuality.

彼女は毎日遅刻してるのに、自分に時間を守るように言ってくるのはどういう神経をしてるのか (Literally 'what kind of nerve does she have to lecture me about punctuality')

So, in most cases, that sense of 神経 is used in the form of どんな神経 although there are phrases like 神経が太い/図太い神経をしている etc.