1.These fundamental questions are often addressed by religion and by our sense of aesthetics, by spiritual feelings, feelings of values.
-These fundamental questions are often addressed by religion and our sense of aesthetics.
This is a passive construction that can be rewritten like this:
Religion and our sense of aesthetics often deal with these fundamental questions...
-by our spiritual feeling, our feelings of values, is additional informtion about how the fundamental questions are addressed.
It could be rewritten in this manner:
These fundamental questions are often addressed by spiritual feelings, by feelings of values, by religion, and by our sense of aesthetics,
2.Medical experts believe that inserting needles into the body at precise points can stimulate nerves that cause the brain to release its natural pain-killing chemicals.
-" that cause the brain to release its natural pain-killing chemicals" is a defining relative clause that defines the noun 'nerves'.
The subject of the clause is the relative pronoun- that. It replaces the noun 'nerves' in the relative clause. Nerves cause the brain to.....