Page 36 - 2024-bfw-MyersAP4e

messengers, hormones, which travel through the bloodstream and affect other tissues,
including the brain. When hormones act on the brain, they influence our interest in sex,
food, and aggression.
Some hormones are chemically identical to neurotransmitters (the chemical messen-
gers that diffuse across a synapse and excite or inhibit an adjacent neuron). The endocrine
system and nervous system are therefore close relatives: Both produce molecules that act
on receptors elsewhere. But like many family members, they also differ. The speedier ner-
vous system zips messages from eyes to brain to hand in a fraction of a second. Meanwhile,
endocrine messages trudge along in the bloodstream, taking several seconds or more to
travel from the gland to the target tissue. If the nervous system transmits information with
text-message speed, the endocrine system delivers an old-fashioned letter.
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
But slow and steady sometimes wins the race. Endocrine messages tend to outlast the
effects of neural messages. Have you ever felt angry long after the cause of your angry
feelings was resolved (say, your friend apologized for their rudeness)? You may have experi-
enced an “endocrine hangover” from lingering emotion-related hormones.
Prejudice causes stress Research Copyright © Bedford, Freeman & Worth Publishers.
In a moment of danger, the ANS orders the adrenal glands on top of the kidneys to
release epinephrine and norepinephrine (also called adrenaline and noradrenaline). These hor-
mones increase heart rate, blood pressure, and blood sugar, providing a surge of energy to
power our fight-or-flight response. When the emergency passes, the hormones — and the
feelings — linger a while.
The most influential endocrine gland is the pituitary gland, a pea-sized structure located
in the core of the brain, where it is controlled by an adjacent brain area, the hypothalamus
®
AP Science Practice
(more on that shortly). Among the hormones released by the pituitary is a growth hormone
Research that stimulates physical development. Another is oxytocin, which enables orgasm and, in
Because it is easily measured women, labor contractions and milk flow while nursing. Oxytocin also aids social support.
through saliva, cortisol level is a While grooming their children, male baboons’ oxytocin levels surge (Rincon et al., 2020).
common operational definition of By promoting social bonding, oxytocin strengthens communities and enables them to act
stress. Revisit Unit 0 if you need a
refresher on variables and opera- cooperatively against threats (Quintana & Guastella, 2020; Zhang et al., 2019).
tional definitions. Pituitary secretions also direct other endocrine glands to release their hormones. The
pituitary, then, is a maestro gland (whose own director is the hypothalamus). For example,
under the brain’s influence, the pituitary triggers your sex glands to release sex hormones.
These hormones, in turn, influence your brain and behavior (Goetz et al., 2014). So, too,
with stress. A stressful event triggers your hypothalamus to instruct your pituitary to
release a hormone that causes your adrenal glands to flood your body with cortisol, a stress
hormone that increases blood sugar.

demonstrates that an experience of
prejudice may trigger release of the
stress hormone cortisol (Deer et al.,
2018).

hormones chemical messengers
that are manufactured by the
endocrine glands, travel through
the bloodstream, and affect other fizkes/Getty Images
tissues.

36 Unit 1 Biological Bases of Behavior

03_myersAPpsychology4e_28116_ch01_002_163.indd 36 15/12/23 9:21 AM