Topic 11 Endocrine System: Endocrine Glands Flashcards
- Hypothalamus
- Anterior Pituitary
- Posterior Pituitary
- Pineal Gland
- Thyroid
- Parathyroid
- Thymus
- Adrenal Gland
- Pancreas
- Testis
- Ovaries
- Gastrointestinal Hormones
Types of Endocrine Glands
a. Monitors the external environment and internal conditions of the body. The hypothalamus contains neurosecretory cells that link the hypothalamus to the pituitary gland, and is therefore considered the link between the endocrine and nervous system
b. The hypothalamus helps to regulate the pituitary via negative feedback mechanisms and by the secretion of releasing and inhibiting hormones.
c. Hormones Secreted:
d. ADH (vasopressin) and oxytocin to be stored in the posterior pituitary
e. Gonadotropin releasing hormone (GnRH) from neurons, which stimulates the anterior pituitary to secrete FSH and LH
- Hypothalamus
- Mainly regulates hormone production by other glands and is regulated itself by the hypothalamus
- Anterior Pituitary
a. Direct (non-topic) hormones: directly stimulate organs
b. Tropic Hormones
Hormones in Anterior Pituitary
- hGH - aka somatotropin, stimulates bone and muscle growth. Stimulates growth in almost all cells of the body, and does by increasing episodes of mitosis, cell size, rate of protein synthesis, and use of fatty acids for energy. hGH also mobilizes fat stores, decreases use of glucose, increases protein transcription/translation, and decreases protein/amino acid breakdown
a. Direct (non-topic) hormones: directly stimulate organs
- Prolactin
- Melanocyte stimulating hormone (MSH)
- Endorphins
Types of Direct (non-topic) hormones
- Stimulates milk production in females from mammary gland cells. The hypothalamus can inhibit prolactin release. Suckling stimulates the hypothalamus, which stimulates the anterior pituitary → release of prolactin. There is no milk production before birth due to inhibitory effects on it by progesterone and estrogen
Prolactin
- Stimulates melanocytes to produce and release melanin
Melanocyte stimulating hormone (MSH)
- Inhibit perception of pain (is technically a neurohormone)
Endorphins
- Stimulate other endocrine glands
b. Tropic Hormones
- ACTH
- TSH
- LH
- FSH
Types of Tropic Hormones
- Release glucocorticoids via second messenger cAMP. Release of ACTH is stimulated by many types of biological stress, and glucocorticoids are stress hormones
ACTH
- Stimulates thyroid gland which in turn increases in size, cell number, and rate of secretion of hormones T3 and T4. T3 and T4 concentrations have a negative feedback effect on TSH release at both the anterior pituitary and hypothalamus
TSH
- In females, stimulates formation of corpus luteum, and in males, it stimulates interstitial cells of testes to produce testosterone
LH
- In females, stimulates maturation of ovarian follicles to secrete estrogen, and in males, stimulates maturation of seminiferous tubules and sperm production
FSH
- Composed mainly of support tissue from nerve endings extending from the hypothalamus. Does not synthesize hormones, but stores ADH and oxytocin produced by the hypothalamus.
- Posterior Pituitary
a. ADH/Vasopressin
b. Oxytocin
Types of Posterior Pituitary
- Increases reabsorption of water by increasing permeability of the nephron’s collecting duct → water reabsorption and increased blood volume and pressure. Coffee and alcohol block ADH, therefore increasing urine volume
a. ADH/Vasopressin
- Secreted during childbirth, increases strength of uterine contractions and stimulates milk ejection by stimulating contraction of smooth muscle cells in the uterus and mammary glands
b. Oxytocin
- Neural cell bodies of the hypothalamus synthesize the hormones, and are transported down axons to the posterior pituitary where they are released into the blood
Note
- Secretes melatonin which plays a role in the circadian rhythm
- Pineal Gland
- Note that the hypothalamus, pituitary gland, and pineal gland are the endocrine glands in the human brain
Note
- Located on the ventral surface of the trachea, just in front of the trachea
- Thyroid
a. Thyroxine (T4) and triiodothyronine (T3)
b. Calcitonin
c. Disorders of thyroid
Thyroid Types
- Lipid soluble tyrosine derivatives
a. Derived from tyrosine and necessary for growth and neurological development in children, as well as increasing basal metabolic rate (BMR) in the body (negative feedback on TSH)
b. These hormones contain iodine
c. Hypothyroidism - under secretion → low heart rate, respiratory rate, and BMR
d. Hyperthyroidism - over secretion → increased BMR and sweating (both hypo and hyperthyroidism lead to goiter, or enlargement of thyroid gland)
a. Thyroxine (T4) and triiodothyronine (T3)
- Peptide hormone that tones down Ca2+ in blood
a. Stimulates osteoblast activity, which builds up bone by using up the Ca2+ in the blood
b. Decreases plasma Ca2+ by inhibiting its release from bone
c. Decreases osteoclast activity and number
b. Calcitonin
a. Achondroplasia: results in dwarfism
b. Progeria: premature aging, wrinkled skin, arthritis, and arteriosclerosis
c. Disorders of Thyroid
- The thyroid is the only gland that produces more than one category of hormone (tyrosine and peptide). The adrenal cortex and adrenal medulla are considered separate glands
Note
- Four pea-shaped structures attached to the back of the thyroid
- Parathyroid
a. Parathyroid hormone (PTH)
Type of Parathyroid
- Antagonistic to calcitonin
a. Raises Ca2+ concentrations in blood by stimulating release from bone. This increases osteocyte absorption of Ca2+ phosphate from bone, and stimulates osteoclast proliferation
b. Increases renal Ca2+ reabsorption and renal phosphate excretion
c. Increases Ca2+ phosphate uptake from gut by increasing renal production of vitamin D- derived steroid
d. Secretion is regulated by Ca2+ plasma concentration, and parathyroid glands grow or shrink accordingly
a. Parathyroid Hormone (PTH)
- Involved in immune response, secretes thymosins that stimulate WBCs to become T cells that identify and destroy infected body cells
- Thymus
- rest on top of the kidneys and consist of
- Adrenal Gland
a. Adrenal cortex (outer portion)
9. Adrenal Medulla (inner portion)
Types of Adrenal Cortex
- Glucocorticoids (cortisol and cortisone)
- Mineralocorticoids (aldosterone)
- Cortical Sex Hormones
Parts of Adrenal Cortex
- Raise blood glucose levels, which stimulates gluconeogeneis in the liver, and degrades adipose tissue to fatty acids for use as energy
- Also causes degradation of non hepatic proteins and decrease in non-hepatic amino acids. This results in a corresponding increase in liver/plasma proteins, and amino acids
- Cortisol is a stress hormone
- Glucocorticoids (cortisol and cortisone)
- increases reabsorption of Na+ and excretion of K+ in kidneys
- Acts on the distal convoluted tubule and collecting duct of nephron to increase Na/Cl reabsorption and K+/H+ secretion.
- This net gain in particles in the plasma causes passive reabsorption of water in the nephron → rise in blood volume/pressure (secondary effect)
- Has the same effect, but to a lesser extent, on sweat glands, salivary glands, and intestines
- Mineralocorticoids (aldosterone)
- Androgens are male sex hormones; a small amount is secreted, which is significant in females but not in males, since they have testes producing much more
- Cortical Sex Hormones
a. Epinephrine and norepinephrine
Parts of Adrenal Medulla
- (adrenaline and noradrenaline) - fight or flight catecholamines
a. The “fight or flight” response affects target tissue similar to the role in the sympathetic NS, but lasts longer; considered stress hormones
b. Glycogen → glucose, vasoconstrictor to internal organs + skin, but vasodilator to skeletal muscle; increases heartbeat and blood pressure
c. Increase metabolic activities (glycogenolysis, lipolysis)
d. Increase blood flow to the brain
a. Epinephrine and norepinephrine
- Has bundles of cells called Islet of Langerhans which contain two cell types: alpha and beta; also has delta cells
- Pancreas
a. Alpha cells secrete glucagon
b. Beta cells secrete insulin
c. Delta cells release somatostatin
Parts of Pancreas
- Catabolic, and released when energy is low, thus raising blood glucose levels
a. Stimulates liver to convert glycogen → glucose
b. Stimulates gluconeogenesis in liver
c. Adipose tissue → blood lipids
a. Alpha cells secrete glucagon
- Anabolic, released when blood levels of carbohydrates/proteins are high, thus lowering blood glucose levels
a. Stimulates liver (and most other body cells) to absorb glucose
b. Liver and muscle cells convert glucose → glycogen
c. Fat cells convert blood lipids → adipose tissue storage
d. Works on most body cells (except for neurons of brain and a few others) to become highly permeable to glucose
e. Insulin is derived from pre-proinsulin and pro-insulin. These precursor molecules undergo hydrolysis reaction that modify them to active insulin. Specific protease enzymes cleave two peptide bonds → allows mature insulin to form
b. Beta cells secrete insulin
- Somatostatin inhibits both insulin and glucagon. Possibly increases nutrient absorption time. Suppresses release of GI hormones, which decreases the rate of gastric emptying and rate of blood flow to intestines
c. Delta cells release somatostatin
a. Testosterone
Part of Testis
- Spermatogenesis, secondary sex characteristics
a. Testosterone
a. Estrogen
b. Progesterone
c. Male and Female Development
Topics on Ovaries
- Menstrual cycle, secondary sex characteristics
a. Estrogen
- Menstrual cycle, pregnancy, regulates formation of internal reproductive structures
b. Progesterone
- In XX organism, the Mullerian duct differentiates into oviduct, and Wolffian ducts degenerate. In XY, Wolffian develops into male reproductive structures, and Mullerian duct degenerates.
a. SRY genes are present on Y chromosomes; in its absence, ovaries develop. In its presence, sertoli cells form, which produce a signal that inhibits formation of Mullerian ducts.
b. The Leydig cells that form from the presence of the Y chromosome produce testosterone that causes Wolffian duct to further develop
c. Male and Female Development
a. Gastrin
b. Secretion
c. Cholecystokinin
Types of Gastrointestinal Hormones
- Breaks down food in stomach, stimulates secretion of HCl
a. Gastrin
- Small intestine; when acidic food enters from stomach, this neutralizes acidity of chyme by stimulating the release of alkaline bicarbonate from the pancreas
b. Secretion
- Small intestine; presence of fats causes contraction of gall-bladder and release of bile, which is involved in the digestion of fats and tells pancreas to release enzymes for digestion
c. Cholecystokinin