Self And The Phenomenon Of Life: A Biologist Examines Life From Molecules To Humanity

Self and Emotion 193

“9x6” b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity

and skin. In contrast, interoceptive visceral sensations, which include
palpitation, chest oppression, shortness of breath, stomach cramps, and
intestinal spasm, are mainly outcomes of sympathetic discharge that feed
back to the brain through sensory components of the autonomic nervous
system.^31 Anatomically, most visceral sensations are carried in the affer-
ent fibers of the Vagus nerve to a relay in the nucleus tractus solitarius
(in medulla), from where fibers are sent to the parabrachial nucleus (in
pons) and finally reaching the insular cortex for conscious experience.
This feedback sensation from autonomic activity is what William James
referred to as “emotion” a hundred years ago.

9.7 Role of Chemicals and Hormones

A number of chemicals and hormones are crucial to the mechanism of
emotion in humans.^32 Dopamine is the major neurotransmitter that acti-
vates the nucleus accumbens and other areas of the mesolimbic pathway,
the motivation/reward center of the brain. When infused into the brain
it promotes drive and reduces sadness. Oxytocin, a hormone secreted by
the posterior pituitary, enhances trust and attachment among persons,
including mother-and-child, sexual partners, and friends. Vasopressin,
another hormone from the posterior pituitary, increases sexual arousal
and attraction and decreases anxiety. Lack of serotonin is correlated
with depression, anxiety, and obsessive thinking. Adrenaline and cortisol
in the blood promote alertness and decrease pain sensitivity. Testoster-
one stimulates aggressive behavior and increases libido in both sexes. In
rats, repeated social stress promotes the release of adrenal glucocorti-
coids (such as cortisol), and induces social aversion and anxiety through
action on the nucleus accumbens and frontal cortex.^33 The number of
mood-changing and psychotropic drugs, along with their endogenous
counterparts (endorphins, enkephalins, the endocannabinoids, etc.), is
too numerous to enumerate here. (The role of hormones in social behav-
ior is further elaborated in Chapter 12: The Expanded Self: Society as
Self.)