Organs of the Endocrine System

and Related Hormones

Hypothalamus

1. Collects information from the body. Integrates the nervous system and Endocrine system responses to maintain homeostasis.

2. Hormones: Hypothalamic Releasing Hormone and Hypothalamic Non-releasing Hormone stimulate or inhibit the pituitary gland.

Pituitary

1. Two parts: Anterior Pituitary and Posterior Pituitary2. Can act directly on target tissue or stimulate other endocrine glands.3. Hormones Anterior Pituitary:

a. Tropic Hormones, stimulate other endocrine glands.i. Adrenocorticotropin (ACTH) Stimulates the adrenal cortex

to release steroid hormones.ii. Thyroid-stimulating hormone (TSH) acts on the thyroid to

stimulates the release of two thyroid hormones thyroxine(T4) and triiodothyronine (T3).

Anterior pituitary: Tropins continued

i. Follicle-stimulating hormone (FSH) stimulates the production of estrogen and eggs in women, and production of sperm in men.

ii. Luteinizing hormone (LH) acts on ovaries to produce progesterone an estrogen in women. Also signals the release of eggs. In men stimulates the interstitial cells in the testes to produce testosterone.

Anterior pituitary: Other Hormones

a. Stores and releases hormones from the hypothalamus.b. Growth hormone (GH) acts directly on body tissues.

Responsible for the growth and development of the body. Also important in the breakdown of fats and proteins into useable energy, during exercise.

c. Prolactin stimulates the growth of the mammary glands and milk production in a nursing mother.

https://www.youtube.com/watch?v=2ALEMLZKnfA

Posterior Pituitary

1. Hormones of the Posterior Pituitary, the posterior pituitary stores rather than produces hormones:

a. Antidiuretic hormone targets the kidneys, decreases urine output, increasing fluid volume in the body.

i. Secreted when plasma volume (the liquid portion of the blood) gets low due to dehydration or profuse sweating.

ii. Subject to humoral control.iii.Also plays a role in controlling blood pressure.

b. Oxytocin secreted by pregnant women during labor and continues to be secreted for as long as the woman is nursing.

Thyroid

1. Located near the larynx, controls metabolism. 2. Hormones of the Thyroid:

a. Thyroid hormone: Thyroxine (T4) and Triiodothryonine (T3) Responsible for controlling energy metabolism and heat production of the body.

b. Calcitonin when calcium levels in the blood rise, calcitonin is released to facilitate uptake of calcium by the bones. It also reduces absorption of calcium by the kidneys and intestines.

a. Subject to humoral control

b. Produced mostly during childhood.

Parathyroid

1. Two pairs of glands located on the posterior of the thyroid.2. Hormone: Parathyroid hormone (PTH) secreted in response to

low blood calcium. a. Stimulates the breakdown of bone tissues, which releases

calcium into the blood. b. Increases absorption of calcium in the intestines with the aid

of vitamin Dc. Stimulates reabsorption of calcium from the kidneys.

Thymus and Pineal Gland

Thymus

1. Both an endocrine gland and a lymphatic organ. It grows smaller with age. Inhibited by cortisol production.

2. Hormone: Thymosin essential for the development of white blood cells. Which plays an important role in the body’s immune system.

Pineal Gland

1. Small gland located in the brain and contains the epithalamus.2. Hormone: Melatonin produced when the body is exposed to

darkness, causes sleepiness.

Adrenal Glands: Adrenal medulla

1. A pair of glands that sit on top of the kidneys.2. Two parts: the adrenal cortex and the adrenal medulla.

a. The adrenal cortex functions as a glandb. The adrenal medulla is part of the nervous system.

3. Hormones of the Adrenal Medulla: epinephrine (adrenalin) and norepinephrine stimulated into production by the sympathetic nervous system, during physical and emotional stress. Increased breathing, heart rate, blood pressure. Change in blood flow to redistribute resources to the muscles.

Adrenal Cortex1. Hormones of the Adrenal Cortex, stimulated through hormonal

control by the anterior pituitary: a. Mineralocorticoids, regulate sodium:

i. Aldosterone stimulate the reabsorption of sodium and water by the kidneys and the elimination of potassium. Major role in regulating blood pressure and blood electrolyte concentrations.

b. Glucocorticoids, regulate sugar:i. Cortisone and Cortisol converts fats and amino acids into

glucose. This insures the brain and nervous system always has a constant supply of glucose.

c. Sex Hormones: i. Estrogen and Androgens, primarily testosterone

released in small amounts but steadily throughout life.

Pancreas

1. Regulates blood sugar levels in the blood.a. Hormones:

i. Insulin causes the body’s cells to take up glucose for energy use which reduces blood glucose. Stimulates the liver to convert excess glucose into glycogen.

ii. Glucagon increases blood glucose by stimulating the liver to begin braking down glycogen into glucose.

Gonads

1. Sex glands, testes in men, ovaries in women.2. Hormones:

a. Testosterone produced by the testes, responsible for sperm production, development of the male reproductive system and the emergence of male secondary sexual characteristics during puberty.

b. Estrogen and progesterone development of the female reproductive glands and secondary sexual characteristics. Regulates the menstrual cycle and promotes breast development.

Other Hormones

1. Some hormones are actually produced by the tissues rather than endocrine glands.

a. Erythropoietin released by the kidneys, stimulates red blood cell production.

b. Prostaglandins released by fatty tissue, regulates smooth muscle cells, and activates the inflammatory response.

c. Leptin released by adipose tissue, fatty tissue, reduces appetite and increases energy production.