Invitation to Psychology

462 ChapTER 13 Emotion, Stress, and Health

changes that are adaptive in the short run, be­

cause  they permit the body to respond quickly

to  danger, can become hazardous in the long

run. Modern researchers are learning how this

happens.

When you are under stress, your brain’s

hypothalamus sends messages to the endocrine

glands along two major pathways. One, as Selye

observed, activates the sympathetic division of

the autonomic nervous system for fight or flight,

producing the release of epinephrine and nor­

epinephrine from the inner part (medulla) of

the adrenal glands. In addition, the hypothala­

mus initiates activity along the HPA axis (HPA

stands for hypothalamus–pituitary– adrenal cor­

tex): The hypothalamus releases chemical mes­

sengers that communicate with the pituitary

gland, which in turn sends messages to the outer

part (cortex) of the adrenal glands. The adrenal

cortex then secretes cortisol and other hormones

that elevate blood sugar and protect the body’s

tissues from inflammation in case of injury. (See

Figure 13.3.)

HPA (hypothalamus–
pituitary–adrenal
cortex) axis A system
activated to energize
the body to respond to
stressors. The hypo-
thalamus sends chemi-
cal messengers to the
pituitary gland, which in
turn prompts the adrenal
cortex to produce cortisol
and other hormones.

3

The exhaustion phase, in which persistent stress

depletes the body of energy, thereby increas­

ing vulnerability to physical problems and illness.

The same reactions that allow the body to respond

effectively in the alarm and resistance phases are

unhealthy as long­range responses. Tense muscles

can cause headache and neck pain. Increased blood

pressure can become chronic hypertension. If nor­

mal digestive processes are interrupted or shut

down for too long, digestive disorders may result.

Selye did not believe that people should aim

for a stress­free life. Some stress, he said, is posi­

tive and productive, even if it also requires the

body to produce short­term energy: competing in

an athletic event, falling in love, or working hard

on a project you enjoy. And some negative stress is

simply unavoidable; it’s called life.

Explore the Concept Selye’s General Adaptation

Syndrome at MyPsychLab

Current Approaches. LO 13.10 One of Selye’s

most important observations was that the biological

PATHWAY 1 PATHWAY 2

Secretes epinephrine

and norepinephrine

Secretes cortisol

and other hormones

Stomach

Cortex

Colon

Small

intestine

Adrenal gland

Medulla

Autonomic Nervous System

(sympathetic division)

Adrenal Cortex

(outer part of adrenal gland)

Adrenal Medulla

(inner part of adrenal gland)

Hypothalamus Hypothalamus

Pituitary

FIgURE 13.3 The Brain and Body Under Stress

When a person is in danger or under stress, the hypothalamus sends messages to the endocrine glands along two

major pathways. In one, the hypothalamus activates the sympathetic division of the autonomic nervous system, which

stimulates the adrenal medulla to produce epinephrine and norepinephrine. The result is the set of bodily changes

associated with fight or flight. In the other pathway, messages travel along the HPA axis to the adrenal cortex, which

produces cortisol and other hormones. The result is increased energy and protection from tissue inflammation in case

of injury.