nervous strain vs nerves

nervous strain and nerves both are nouns.

Word	Noun	Adjective	Verb	Adverb
nervous strain	Yes	No	No	No
nerves	Yes	No	No	No

As nouns, nerves is a hypernym of nervous strain; that is, nerves is a word with a broader meaning than nervous strain:

Other hypernyms of nervous strain include nervousness.

nervous strain (noun)	nerves (noun)
(psychology) nervousness resulting from mental stress	control of your emotions
	an uneasy psychological state