What do endocrine glands secrete directly into the bloodstream?
Hormones
How are hormones transported throughout the body?
By the bloodstream
What are hormones in the endocrine system?
Chemical messengers producing effects on target cells or organs
What effect do hormones have on target cells or organs?
They produce a specific effect
What experiment did Berthold perform in 1849 with roosters?
He castrated roosters and replaced their testes
What behaviors were restored in roosters after testis replacement in Berthold's 1849 study?
Crowing, fighting, mating behavior, body size, and feathers
What did Berthold's 1849 rooster experiment suggest about the substance from testes?
It entered the bloodstream and was not nerve-connected
In which year did Berthold publish his rooster castration experiment?
1849
Which hormones diffuse through the lipid bilayer to bind inside target cells?
Lipid-soluble hormones such as testosterone, estrogen, and cortisol.
Where do lipid-soluble hormones bind to activate specific genes?
Inside target cells on receptor proteins.
Why can't water-soluble hormones cross the cell membrane?
Because they are not lipid-soluble and cannot diffuse through the lipid bilayer.
How do water-soluble hormones trigger intracellular reactions?
By binding to surface receptors on target cells.
Name four water-soluble hormones that bind to surface receptors.
Epinephrine, human growth hormone, thyroxine, and insulin.
What is negative feedback in homeostasis?
A response where system output inhibits its own activity.
What triggers ADH release from the posterior pituitary?
Hypothalamic receptors detect too concentrated blood plasma.
How does ADH affect the kidneys?
It makes them retain water.
What stops ADH release after plasma concentration normalizes?
The hypothalamus signals the pituitary to stop releasing ADH.
What does the hypothalamus release in a tropic hormone pathway?
A releasing hormone into the anterior pituitary.
What does the anterior pituitary release in response to hypothalamic hormones?
A tropic hormone into the blood.
What does the tropic hormone stimulate?
Another endocrine gland.
What inhibits further hormone release in a tropic hormone pathway?
The final hormone produced.
What lobes does the pituitary gland have and how many hormones does it release?
It has anterior and posterior lobes and releases eight hormones.
Which hormones does the anterior pituitary produce and release?
Human growth hormone, prolactin, TSH, ACTH, FSH, and LH.
What functions does human growth hormone regulate and stimulate?
It regulates growth, development, metabolism, and stimulates muscle, connective tissue, bone growth, protein synthesis, cell division, and fat release.
What effect does thyroxine have on metabolism and cellular respiration?
It increases metabolism of fats, proteins, carbohydrates and stimulates cellular respiration in heart, muscle, liver, and kidneys.
How is thyroxine secretion controlled by negative feedback?
TSH stimulates thyroxine release, and rising thyroxine suppresses hypothalamic and pituitary TSH release.
How does calcitonin regulate blood calcium levels?
By stimulating calcium uptake into bones when blood calcium is too high.
When is parathyroid hormone released in the body?
When blood calcium levels fall.
Name one effect of parathyroid hormone on calcium regulation.
It stimulates bone breakdown to raise blood calcium.
How does parathyroid hormone affect kidney function?
It stimulates kidney calcium reabsorption.
What role does parathyroid hormone play in vitamin D?
It activates vitamin D.
How does parathyroid hormone influence intestinal calcium?
It stimulates intestinal calcium absorption.
Where are the adrenal glands located relative to the kidneys?
They lie on top of the kidneys.
What two parts does each adrenal gland contain?
An inner adrenal medulla and an outer adrenal cortex.
What triggers the adrenal medulla to release epinephrine and norepinephrine?
Sympathetic neurons signaling it directly.
What physiological changes occur during the adrenal medulla's fight-or-flight response?
Increased breathing rate, heart rate, blood pressure, blood flow to heart and muscles, and liver glycogen breakdown.
What is cortisol's main role in blood glucose regulation?
It raises blood glucose by promoting muscle-protein and fat breakdown.
Which cells secrete insulin in the pancreas?
Beta cells in the islets of Langerhans.
What effect does insulin have on target cells?
It makes them more permeable to glucose.
How does insulin affect glucose storage in the liver?
It promotes glucose storage as glycogen.
When is glucagon released by alpha cells?
During rigorous exercise or fasting.
What does glucagon stimulate the liver to do?
Convert glycogen into glucose and release it into the blood.
What causes diabetes mellitus in the body?
Lack of insulin production or response causing high blood glucose.
What immune process causes type 1 diabetes?
Destruction of pancreatic beta cells.
How does type 2 diabetes develop?
Gradual insulin receptor resistance.
Where is antidiuretic hormone created and stored?
Created in hypothalamus, stored in posterior pituitary.
When is antidiuretic hormone released?
When blood plasma is highly concentrated.
What effect does antidiuretic hormone have on kidney nephrons?
Makes them absorb more water into the blood.
What causes diabetes insipidus?
Insufficient ADH production.
How is diabetes insipidus treated and how is it unrelated to diabetes mellitus?
Treated with ADH medication and unrelated to insulin or glucose.
Approximately how many hormones or hormone-like chemicals do humans have?
Over 200.
What biological processes do human hormones regulate?
Growth, development, metabolism, homeostasis, and immunity.
Why is iodine important for thyroid hormone production?
Iodine is required to make thyroid hormones.
What happens if iodine is inadequate for thyroxine production?
Thyroxine production stops and relentless TSH stimulation enlarges the thyroid into a goitre.
How many parathyroid glands are attached to the thyroid gland?
Four small parathyroid glands.
How does high cortisol affect ACTH production?
It suppresses ACTH production by negative feedback to the hypothalamus and anterior pituitary.
Name two health effects of sustained high cortisol during chronic stress.
Impaired thinking and high blood pressure.
What are two other consequences of chronic high cortisol besides impaired thinking and high blood pressure?
Damage to the heart and increased susceptibility to infection.
How are the endocrine cells of the pancreas organized?
Into about 2,000 groups called islets of Langerhans.
What was established by removing the pancreas from a dog in 1889?
A relationship between the pancreas and diabetes.
Who isolated insulin in 1921 and where?
Banting at the University of Toronto.
Answer 23 questions on Endocrine System and Hormones.
1. How do endocrine glands deliver their secretions to tissues throughout the body?
2. What best describes a hormone in the endocrine system?
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