Some say that while the Nephesh is fixed in the heart, it spreads outward from there to the rest of the organs, and that it settles in the body’s center from where it irradiates outward to the rest of the body much the way the sun situates itself in the center of the sky. In fact, the body is said to be perched in the Nephesh, the Nephesh is perched in the atmosphere, and the atmosphere is perched in G-d’s presence where everything abides (Zohar Chadash, Breishit 6d). But see Tanya Ch. 9 which differentiates between the “animal” Nephesh which is centered in the left chamber of the heart and the Divine Nephesh which is centered in the brain from where it irradiates outward to the rest of the body as well as the right side of the heart.
R’ Chaim Voloshin depicts the Nephesh as being expressed (and centered) in our actions, the Ruach in our speech, and the Neshama in our thoughts (Nephesh HaChaim 1:14, 16).
Others portray the Neshama as less than rooted in the body, and as something of a free agent if you will, given that it soars upwards out of the body when we sleep (Zohar 1, p. 53a, 121b; Zohar 2, p. 195b; Zohar 3, p. 25a, etc.; also see Ta’anit 11a) after which it returns to us through the nostrils in the morning and doesn’t return to the body proper until we pray in the morning (Zohar Chadash, Ruth, 90d), or to our belly once we say Viddui (the morning confession) (Zohar 1, p. 98a; also see Berachot 8a).