Future Bilingual School for Girls
Chapter 3: The Endocrine System
Section 3.3: Regulation of Body Processes
Learning Objectives
By the end of this section, you will be able to do the following:
Explain how hormones regulate the excretory system
Discuss the role of hormones in the reproductive system
Describe how hormones regulate metabolism
Explain the role of hormones in different diseases
Hormonal Regulation of Stress
When a threat or danger is perceived, the body responds by releasing hormones that will ready it
for the “fight-or-flight” response. The effects of this response are familiar to anyone who has
been in a stressful situation: increased heart rate, dry mouth, and hair standing up.
The sympathetic nervous system regulates the stress response via the hypothalamus. Stressful
stimuli cause the hypothalamus to signal the adrenal medulla (which mediates short-term stress
responses) via nerve impulses, and the adrenal cortex, which mediates long-term stress
responses, via the hormone adrenocorticotropic hormone (ACTH), which is produced by the
anterior pituitary.
Short-term Stress Response
When presented with a stressful situation, the body responds by calling for the release of
hormones that provide a burst of energy. The hormones epinephrine (also known as adrenaline)
and norepinephrine (also known as noradrenaline) are released by the adrenal medulla. How do
these hormones provide a burst of energy? Epinephrine and norepinephrine increase blood
glucose levels by stimulating the liver and skeletal muscles to break down glycogen and by
stimulating glucose release by liver cells. Additionally, these hormones increase oxygen
availability to cells by increasing the heart rate and dilating the bronchioles. The hormones also
prioritize body function by increasing blood supply to essential organs such as the heart, brain,
and skeletal muscles, while restricting blood flow to organs not in immediate need, such as the
skin, digestive system, and kidneys. Epinephrine and norepinephrine are collectively called
catecholamines.
Long-term Stress Response
Long-term stress response differs from short-term stress response. The body cannot sustain the
bursts of energy mediated by epinephrine and norepinephrine for long times. Instead, other
hormones come into play. In a long-term stress response, the hypothalamus triggers the release of
ACTH from the anterior pituitary gland. The adrenal cortex is stimulated by ACTH to release
steroid hormones called corticosteroids. Corticosteroids turn on transcription of certain genes in
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the nuclei of target cells. They change enzyme concentrations in the cytoplasm and affect cellular
metabolism. There are two main corticosteroids: glucocorticoids such as cortisol, and
mineralocorticoids such as aldosterone. These hormones target the breakdown of fat into fatty
acids in the adipose tissue. The fatty acids are released into the bloodstream for other tissues to
use for ATP production. The glucocorticoids primarily affect glucose metabolism by stimulating
glucose synthesis. Glucocorticoids also have anti-inflammatory properties through inhibition of
the immune system. For example, cortisone is used as an anti-inflammatory medication;
however, it cannot be used long term as it increases susceptibility to disease due to its immune-
suppressing effects.
Mineralocorticoids function to regulate ion and water balance of the body. The hormone
aldosterone stimulates the reabsorption of water and sodium ions in the kidney, which results in
increased blood pressure and volume.
Hypersecretion of glucocorticoids can cause a condition known as Cushing’s disease,
characterized by a shifting of fat storage areas of the body. This can cause the accumulation of
adipose tissue in the face and neck, and excessive glucose in the blood. Hyposecretion of the
corticosteroids can cause Addison’s disease, which may result in bronzing of the skin,
hypoglycemia, and low electrolyte levels in the blood.
Answer the following questions:
1. Gow does the sympathetic nervous system regulate stress?
2. What hormones are involved in Short-term Stress Response?
3. How do these hormones provide a burst of energy?
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4. What hormones are involved in long-term Stress Response?
5. What are the effects of hypersecretion and hyposecretion of glucocorticoids?
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