Chapter 13: The Glands and Hormones of the Endocrine System

Human Growth Horomone

(hGH) A hormone that stimulates the production of growth factors from the liver, increases protein synthesis, cell division growth, and metabolic release of stored fats. This hormone is especially important during childhood. Secreted by Anterior Pituitary Gland and targets most cells, especially bone and muscle.

Can affect some tissues but generally tropic.

Endocrine Glands

A group of glands, secrete chemical messengers called hormones directly into the bloodstream, which transports hormones throughout the body.

Hormones

Chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream and affect other tissues. Over 200, regulate growth, development, metabolism and blood pressure.

Pancreas

An endocrine gland that secretes the hormone insulin and the hormone glucagon into the bloodstream, which affects its target cells by making them more permeable to glucose. Located behind the stomach and is connected to the small intestine, much of this tissue secretes digestive enzymes into the small intestine. For this reason the pancreas is also considered an Exocrine Gland which secretes products into ducts. Stimulated directly by glucose levels in blood.

Endocrine System

Made of the endocrine glands and the hormones they secrete. Has slower and longer lasting effects compared to the Nervous System. Also acts on a broader range of cell types.

Capon

A castrated male chicken.

Parathyroid Glands

Four glands embedded in the thyroid but produces different hormones. Produces the parathyroid hormone.

Hypothalamus

Secretes hypothalamic releasing and inhibiting hormones that regulate the anterior pituitary hormones. NOT a gland. Links the nervous and endocrine systems. Regulates heart rate, hunger, water balance, and body temperature.

- Gonadotropin-releasing hormone

- Corticotropin-releasing hormone

- Thyroid-releasing hormone

- Growth hormone-releasing hormone

- Growth hormone-inhibiting hormone

- Prolactin inhibiting factor

Anterior Pituitary Gland

The anterior part of the pituitary gland; an endocrine gland whose secretions are controlled by the hypothalamic hormones. Secretes hgH, TSH, ACTH, FSH, LH, and PRL. Makes it's own hormones.

Thyroid Stimulating Hormone

A hormone that stimulates the thyroid gland. Stimulates the production of thyroxine, triiodothyronine and calcitonin. Secreted by Anterior Pituitary Gland.

Glucocorticoids (cortisol)

A hormone that targets the liver, muscle, and white blood cells, and acts as an anti-inflammatory, suppressing the immune response, long term response to stress (increases energy available for use by cells by increasing blood sugar) Prolonged cortisol = increased blood glucose level and increased inflammation. Produced by the Adrenal Cortex.

Follicle Stimulating Hormone

A hormone that targets ovaries and testes. In females, leads to estrogen release and the maturation of the egg. In males leads to spermatogenesis. Secreted by Anterior Pituitary Gland.

Luteinizing Hormone

A hormone that targets ovaries and testes, stimulates the release of estrogen, progesterone, and testosterone. In females causes ovulation and formation of the corpus luteum. In males stimulates testosterone production Secreted by Anterior Pituitary Gland.

Prolactin

A hormone that stimulates milk production after birth from the mammary glands, the target of the hormone. Made by Anterior Pituitary Gland.

Posterior Pituitary Gland

Also known as the neurohypophysis; it is made up of nervous tissue/neurons and stores and secretes 2 hormones made by the hypothalamus (oxytocin and ADH); it is controlled by action potentials from the hypothalamus. The "Middle Man". Does not produce its own hormones.

Antidiuretic Hormone

A hormone that promotes the retention of water by the kidneys. Made by the posterior pituitary gland.

Oxytocin

A hormone that targets the uterus, mammary glands and placenta. It increases uterine contractions, triggers milk let down, and stimulates the release of prostaglandins form the placenta (all cause positive feedback to continue production) Secreted by the posterior pituitary gland.

Thyroid

The gland in the neck that secretes hormones that regulate growth, development, and metabolic rate. Secretes Thyroxine and Calcitonin. Stimulated by the anterior pituitary gland.

Thyroxine

A hormone that affects all cells and tissues, increases the rate of fat, protein and carbohydrate metabolism; regulates maturation and growth, and increases sensitivity to epinephrine and norepinephrine. Secreted by the Thyroid.

Calcitonin

A hormone that targets bones, small intestine and kidneys to lower blood calcium by inhibiting the release of calcium from the bones and reabsorption of calcium by kidneys. Secreted by the Thyroid.

Parathyroid Hormone

(PTH) A hormone that raises blood calcium levels by stimulating the bone cells to release calcium, the blood to have increased calcium concentration, the intestine to absorb calcium from food, and the kidneys to reabsorb calcium. Secreted by Parathyroid.

Adrenal Cortex

The outer section of each adrenal gland; secretes cortisol (a glucocorticoid), aldosterone (mineralocorticoids), and sex hormones (gonadocorticoids). Stimulated by the anterior pituitary gland. Long term stress response.

Mineralocorticoids

Secreted by the adrenal cortex and targets the distal tubule of the kidneys. It is important in increasing blood pressure by stimulating kidneys to increase the absorption of sodium into the bloodstream (higher solute concentration = more water drawn from the nephrons = higher blood pressure) A long term response to stress (increases deliver of O2 and other nutrients to cell.) Secreted by the Adrenal Cortex, Eg. aldosterone.

Gonadocorticoids

A hormone that promotes secondary sexual characteristics. Found in the Adrenal Cortex.

Adrenal Medulla

A gland that secretes epinephrine and norepinephrine, which are fight or flight hormones that raise blood glucose levels. Stimulated by the hypothalamus.

Insulin

A hormone secreted by the islets of langerhans that targets the liver, muscle cells, and other organs. Makes cells more permeable to glucose after a meal, decreasing blood glucose concentration. Promotes the temporary storage of glucose as glycogen in the liver. Secreted by the pancreas.

Non-target hormones.

Affect many cells in the body. Eg. Insulin.

Target Hormones

Affect a particular type of cell. Eg. Gastrin.

Exocrine Glands

Secrete chemical substances into ducts that lead either to other organs or out of the body, does not secrete directly into bloodstream like the endocrine glands.

interstitual fluid

The ECF (Extracellular Fluid) that fills the narrow spaces between cells of tissues.

Homeostasis

A tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry, such as blood glucose, around a particular level. In terms of hormones:

-Hormone levels fall = Nervous system triggers hormone release from endocrine glands.

-Hormone levels rise = Nervous system triggers endocrine glands to stop releasing hormones

Hypothalamus Pituitary Complex

The "command center" of the endocrine system that secretes several hormones that directly produce responses in target tissues, as well as hormones that regulate the synthesis and secretion of hormones of other glands. In addition, the hypothalamus-pituitary complex coordinates the messages of the endocrine and nervous systems.

Tropic Hormones

Hormones that stimulate other glands to release their hormones. Released from hypothalamus and pituitary glands.

Peptide Hormone

Hormones made of short chains of linked amino acids such as oxytocin.

Amine Hormone

Also called monoamine hormone. A hormone composed of a single amino acid that has been modified into a related molecule. Eg. norepinephrine's carboxyl group is replaced with a benzene ring.

Protein Hormone

Long chains of linked amino acids such as hGH.

Steroid Hormones

Hormones derived from the lipid cholesterol such as testosterone and progesterone.

PEG

Non-tropic hormones found in the Anterior Pituitary Gland: Prolactin, endorphin, growth hormone.

FLAT

Tropic Hormones found in the Anterior Pituitary Gland: follicle-stimulating hormone, Luteinizing Hormone, Adrenocorticotropic Hormone, Thyroid Stimulating Hormone.

Parathyroid

In the neck; controls the calcium levels in your body, and normals the bone growth. Stimulated by calcium.

Ovaries

Glands that produce the egg cells and hormones in a female. Also produce estrogen and progesterone. Stimulated by the anterior pituitary gland.

Estrogen

A hormone that stimulates uterine lining growth and promotes development of the female secondary sexual characteristics, targets the female reproductive system and causes the development of female sex characteristic while maintaining the functioning of the reproductive system. Secreted by the ovaries.

Progesterone

A hormone that promotes the growth of uterine lining and prevents uterine muscle contraction. Targets the mammary glands and the uterus, prepares the uterus for pregnancy.Secreted by the ovaries.

Testes

2 small organs that are found inside the scrotum, are responsible for making sperm and are also involved in producing a hormone called testosterone. Stimulated by the anterior pituitary gland.

Testosterone

A hormone that promotes sperm formation and the development of male secondary sexual characteristics. Targets organs, muscles, skin, and hair. Causes development of male sex characteristics, larger and stronger muscles, tougher skin. Secreted by the testes.

Water Soluble Hormone

Protein, peptide, or amino acid derivatives, cannot cross the lipid membrane, binds to receptor sites ON the cell membrane. Eg. hGH, epinephrine, insulin, adrenaline, noradrenaline, TSH.

Fat Soluble Hormone

Cholesterol based, diffuse across lipid membrane, bind to receptor sites INSIDE the cell.

Eg. sex hormones, glucocorticoids, mineralcorticoids.

Releasing Factors

Hormones secreted by the hypothalamus, stimulate endocrine glands to produce particular hormones. Eg. gonadotropin releasing hormone (GnRH), corticotropin releasing hormone (CRH), thyroid releasing hormone (TRH), growth hormone releasing hormone (GHRH).

Inhibiting Factors

Hormones secreted by the hypothalamus, prevent endocrine glands from producing particular hormones. Eg. growth hormone inhibiting hormone (GHIH), prolactin inhibiting factor (PIF).

Beta Cells

Cells within the pancreas that secrete insulin, decreasing the levels of blood glucose.

Alpha Cells

Cells within the pancreas that secrete glucagon, increasing the levels of blood glucose.

Islets of Langerhans

Specialized clusters of cells in the pancreas that secrete hormones in the bloodstream responsible for glucose regulation. Secretes both insulin and glucagon which have antagonistic effects).

Non-tropic hormone

A hormone that directly influences non-endocrine tissues.

Negative Feedback

Returns a system to homeostasis, inhibits or counteracts the stimulus that sets off the response.

Eg. Blood sugar, after eating, blood sugar rises, releasing insulin from pancreas. This stimulates cells to become permeable to sugar, causing blood sugar levels to fall and insulin production to cease.

Positive Feedback

Takes the body further from homeostasis, exaggerates or increases the stimulus that sets off a response; often to accomplish a discrete physiological event (e.g. birth).

Eg. Continued exposure to cold causes the body to draw heat from extremities towards critical systems which leads to even further cooling.

antidiuretic hormone (ADH)

A hormone that promotes retention of water by kidneys. When blood plasma becomes too concentrated, receptors in the hypothalamus send a neural signal to the posterior pituitary gland to release ADH. This targets nephrons, making them more permeable to water thus allowing more water reabsorption. After this is done, a signal is sent to stop secreting ADH.

Diabetes Insipidis

When a person is unable to produce ADH leading to large urine volumes leading to ion loss in the blood. Can be corrected by administering ADH.

Portal System

A blood pathway that begins and ends in capillaries, carries releasing hormones from the hypothalamus to the anterior pituitary and these hormones either stimulate or inhibit the release of hormones from this gland.

Neurosecretory Cells

Neurons that secrete neurohormone rather than neurotransmitter.

Hyposecretion of hGH

Leads to dwarfism, fatigue, and anxiety.

Hypersecretion of hGH

Leads to gigantism and acromegaly.

Gigantism

Occurs when the pituitary glands secrete excessive amounts of hGH during childhood.

Pituitary Dwarfism

Occurs when there is insufficient hGH production during childhood leading to extremely small stature but typical adult proportions.

Acromegaly

When someone who reaches adulthood and complete skeletal growth but still has an overproduction of hGH. The excess hGH can no longer cause an increase in height, so the bones and soft tissues of the body widen. Thus, over time, the face widens, ribs thicken, and feet and hands enlarge. Also can lead to cardiovascular diseases, sugar intolerance, diabetes, breathing problems, muscle weakness, and colon cancer.

GHRH

Growth hormone-releasing hormone, secreted by the hypothalamus.

Somatostatin

Inhibits secretion of growth hormone (GH) and thyroid-stimulating hormone (TSH).

Hyposecretion of Thyroxine

Leads to cretinism in children and myxedema in adults.

Cretinism

Lack of thyroxine from birth or before birth. Could be from lack of thyroid gland or lack of iodine in other, leads to severe and irreparable mental defects, stunted growth and reduced growth/function of many organs

Myxedema

Caused by extreme deficiency of thyroid secretion; also known as adult hypothyroidism, leads to goiter formation and low energy.

Grave's Disease

An autoimmune disorder that is caused by hyperthyroidism and is characterized by goiter and/or exophthalmos. Body attacks thyroid leading to swelling of muscles around eyes.

Hypersecretion of Thyroxine

Leads to grave's disease, anxiety, insomnia, heat intolerance, irregular heartbeat, and weight loss.

Goiter

The enlargement of the thyroid gland.

Hyposecretion of Calcitonin

Leads to elevated calcium levels in the blood and increased activity of skeletal muscles and neurons.

Hypersecretion of Calcitonin

Leads to low calcium in blood leading to osteoporosis which is low bone mass due to a more porous bone = higher fracture risk.

Calcium

Essential for healthy teeth and skeletal development, also plays a role in blood clotting, nerve conduction, and muscle contraction.

Hyposecretion of PTH

Leads to decreased calcium concentration in the blood (later leading to osteoporosis) and tetany (muscular spasm).

Hypersecretion of PTH

Leads to increased calcium concentration in the blood. Activates vitamin D and leads to the absorption of calcium from food in intestine.

Bone

Dense, hard connective tissue composing the skeleton, made of calcium phosphate.

Hyposecretion of Testosterone

Lack of secondary sex characteristics.

Hypersecretion of Testosterone

Exaggerated sex characteristics, agression.

Epinephrine and Norepinephrine

Produced by the adrenal medulla, targets liver, muscle, heart, lungs, vessels and brain. Regulates "Fight or flight". Increases breathing, heart rate, blood pressure, blood flow to heart/muscles/brain, glycogen converted to glucose in the liver, and glucose released to the bloodstream. Causes bronchioles and pupils to dilate. Rapid response due to being regulated by nervous system.

Hypersecretion of Epinephrine and Norepinephrine

Leads to hypertension, hyperglycemia, and nervousness.

Neuroendocrine Structure

The adrenal medulla is considered the following because, In the developing embryo, sympathetic neurons and adrenal medulla cells are both formed from nervous system tissue.

Adrenocorticotropic Hormone

Secreted by the anterior pituitary gland, targets the adrenal cortex, stimulates the production of cortisol and aldosterone.

Cortisol

Stress hormone released by the adrenal cortex, a glucocorticoid, Prolonged cortisol exposure leads to elevated blood glucose levels and decreased inflammation throughout the body.

Hyposecretion of Glucocorticoids

Causes Addison's disease.

Hypersecretion of Glucocorticoids

Causes Cushing's disease.

Addison's Disease

Results from damage to the adrenal cortex, causing the body to produce inadequate amounts of mineralocorticoids and glucocorticoids.

Cushing's Disease

Elevated cortisol, causes a high blood glucose concentration, weight gain, sweating, and "moon face".

Hyposecretion of Insulin

Causes diabetes type I (Diabetes type II develops if cells become insensitive to insulin).

Hypersecretion of Insulin

Causes hypoglycemia (low blood sugar). Leads to fatigue and tiredness.

Glucagon

A hormone that raises blood glucose levels by converting glycogen to glucose. Secreted by alpha cells of the islets of Langerhans which targets the liver, promoting the breakdown of glycogen in the liver which is then released into the bloodstream (increasing blood glucose concentration) Secreted by the pancreas.

Hyposecretion = hypoglycemia

Hypersecretion = hyperglycemia

Diabetes Mellitus

Causes blood glucose levels to rise sharply after meals (hyperglycemia). Cells cannot properly obtain the glucose they require for metabolism; individuals become fatigued. Body compensates by metabolising fats and proteins instead of glucose. These are more difficult to break down, and release ketones, a toxic by-product which causes bad breath. Excess glucose in the bloodstream is excreted through urine; high amounts of urine are produced due to changes in osmotic gradient (can lead to frequent urination and thirst).

Untreated = blindness, kidney failure, nerve damage, gangrene, and alpha cell death.

Type 1 Diabetes

Diagnosed in childhood. Immune system produces antibodies that attack and destroy the beta cells of the pancreas. Leads to decreased insulin production. Treated with daily insulin injections.

aka Juvenile diabetes/insulin dependent diabetes.

Type 2 Diabetes

Develops over time. Cell receptors stop responding to insulin, or beta cells produce less insulin. Often associated with poor diet and lack of exercise (not always though; genetic predisposition). Treated with either insulin injections before meals (if insulin production is low) OR diet, exercise and sulfonamides (if cells do not respond appropriately to insulin).

Aka adult onset/non-insulin dependent diabetes.

Type 2 can develop into type 1.

Makes up 90% of all diabetes.

Diabetes Insipidus

Occurs when there is a hyposecretion of ADH. Affected individuals produce large volumes of urine, resulting in the loss of ions from the blood. Continuous risk of dehydration. Can occur during pregnancy, as components of the placenta are known to break down ADH. Treated by administering ADH.

Oskar Minkowski

In 1889, removed part of the pancreas from a dog which then caused the dog to develop diabetes.

Frederick Banting

Isolated insulin from islands of langerhans of dogs.

Insulin Pump

A portable, battery-powered device that delivers insulin through the abdominal wall in measured amounts mimicking the patterns of insulin release.