tree; shrub; bush; wood; timber
autonomic nervous system; ANS
chief; main; principal; major
internal organs; viscera; intestines
regulation; adjustment; control
unconsciousness; unconscious; involuntary; the unconscious (psychoanalysis)
inside; within; while (e.g. one is young); during; among; amongst; in (secret, chaos, poverty, etc.)
environment; circumstance
depending on; dependent on
deflation; contraction; shrinking; constriction
one's heart rate; pulse rate
increase; rise; growth; addition; increment
conscious; deliberate; intentional
to do; to undertake; to send; to dispatch; to put; to move; to give (esp. to someone of equal or lower status)
that is to say; that is; in short; in brief; clogging; obstruction; shrinkage
usual; normal; everyday; usually; normally; generally
before one knows it; before one realises; without one's knowledge; without noticing
eye; eyeball; eyesight; sight; look; stare; notice
heart; guts; nerve; central part
sexual arousal; sexual excitation
purpose; goal; aim; objective; intention
homeostasis; homoeostasis; constancy
system; lineage; corollary; system (range of strata that correspond to a particular time period); (taxonomical) series
parasympathetic nerve system; parasympathetic nervous system
to keep; to preserve; to hold; to last; to endure; to keep well (food)
to feel; to sense; to experience
fight; battle; combat; struggle (for rights, higher wages, etc.); strife; (labor) dispute
confrontation; to face; to confront; to encounter
even if; (it doesn't matter) whether (A or B or ...); whatever; should