Which revision of the sentence is now properly punctuated? the peripheral nervous system—which is a network of nerves extending from your brain and spinal cord to all parts of your body carries signals back and forth. the peripheral nervous system (which is a network of nerves) extending from your brain and spinal cord to all parts of your body carries signals back and forth. the peripheral nervous system which is a network of nerves extending from your brain and spinal cord to all parts of your body carries signals back and forth. the peripheral nervous system—which is a network of nerves extending from your brain and spinal cord to all parts of your body—carries signals back and forth.