Essentials of Anatomy and Physiology

glucose for use by the brain. Cortisol is secreted in any
type of physiological stress situation: disease, physical
injury, hemorrhage, fear or anger, exercise, and
hunger. Although most body cells easily use fatty acids
and excess amino acids in cell respiration, brain cells
do not, so they must have glucose. By enabling other
cells to use the alternative energy sources, cortisol
ensures that whatever glucose is present will be avail-
able to the brain.
Cortisol also has an anti-inflammatory effect.
During inflammation, histaminefrom damaged tis-
sues makes capillaries more permeable, and the lyso-
somes of damaged cells release their enzymes, which
help break down damaged tissue but may also cause
destruction of nearby healthy tissue. Cortisol blocks

the effects of histamine and stabilizes lysosomal mem-

branes, preventing excessive tissue destruction.

Inflammation is a beneficial process up to a point, and

is an essential first step if tissue repair is to take place.

It may, however, become a vicious cycle of damage,

inflammation, more damage, more inflammation,

and so on—a positive feedback mechanism. Normal

cortisol secretion seems to be the brake, to limit

the inflammation process to what is useful for tissue

repair, and to prevent excessive tissue destruction.

Too much cortisol, however, decreases the immune

response, leaving the body susceptible to infection

and significantly slowing the healing of damaged

tissue (see Box 10–4: Disorders of the Adrenal

Cortex).

The Endocrine System 241

Adrenal cortex

Cortisol

Conserves

glucose

Limits

inflammation

Increases use of

excess

amino acids

Increases use

of fats

ATP

ATP

Adipose tissue

Amino acids

Glucose

Brain

Glycogen

Liver

Most tissues

Figure 10–11. Functions of cortisol.

QUESTION:Which food types will be used for energy by most tissues? Which food type

may be stored?