Endocrine System Part 1 Flashcards
Exocrine glands secrete products through
ducts
Endocrine glands secrete hormones into the
blood
Major endocrine glands
- Pituitary
- Pineal gland
- Thyroid gland
- Parathyroid glands
- Adrenal glands
Hypothalamus controls the
pituitary gland
hypothalamus secretes
- thyrotropin-releasing hormone (TRH)
- Oxytocin
- Vasopressin (ADH)
- somatostatin (SST)
thymus secretes
thymopoietin and thymosins
hearts secretes
atriopeptin
kidneys secrete
calcitriol and erythropoietin
GI tract secretes
CKK, GIP, gastrin, secretin, VIP
pancreatic islets secrete
Glucagon, insulin, somatostatin, pancreatic polypeptide
testes secrete
Androgens
* Spermatogenesis
* Growth
* Secondary sexual characteristics
ovaries secrete
Estrogen
* Oogenesis – egg development
* Breast development
* Ovulation
Progesterone
* From corpus luteum in ovary
* Promotes secretion from endometrium
* Matures breasts for lactation
pituitary gland secretes
- follicle-stimulating hormone (FSH)
- lutenizing hormone (LH)
- adrenocorticotropic hormone (ACTH)
- thyroid-stimulating hormone (TSH)
- Prolactin
- growth hormone (GH)
- melanocyte-stimulating hormone (MSH)
pineal
melatonin
thyroid secretes
calcitonin
parathyroid secretes
parathyroid hormone (PTH)
adrenal glands secrete
Cortex: corticosteroids
Medulla: epinephrine, norepinephrine
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Three major chemical classes of hormones:
- Amines
- Peptides and proteins
- Steroids
Amine Hormones
Derived from the amino acid tyrosine
Catecholamines
* Epinephrine & Norepinephrine
* From adrenal gland (medulla)
Dopamine
* From hypothalamus
Thyroid hormones (Like steroids- fat-soluble)
* T3 & T4 (thyroxine)
* From thyroid gland Tyrosine
Peptide and Protein Hormones
- Synthesized as a preprohormone
- Cleaved to a prohormone in rough ER
- Cleaved to active hormone in Golgi
- Hormone and other fragments secreted together
pancreas secretes
- insulin
- glucagon
- renin (Kidney)
- angiotensin (Liver)
- atrial natriuretic peptide (ANP)
(Heart)
Steroid Hormones
- From a cholesterol precursor (lipids)
- Produced by adrenal cortex and gonads (testes/ovaries)
- Stimulated by anterior pituitary hormones
- Via G-protein coupled receptor
Calcitrol synthesis (Active Vitamin D3)
- Cholesterol-derived precursor (obtained from the diet)
- Converted to Vitamin D3 in skin
- Energy from UV light
- Hydroxyl groups added in liver and kidneys
- Active hormone is 1,25-dihydroxyvitamin D3
- AKA Calcitrol
Peptide & catecholamine hormones
– Hydrophilic
– Water-soluble
– Dissolved in plasma
Steroid and thyroid hormones
– Poorly soluble
– Mostly bound to plasma proteins
– Small concentrations dissolved in plasma
(“free hormones”)
– Only free hormones interact with target cells
Blood concentration depends on:
- Rate of secretion
- Rate of removal
Clearance rates:
- Peptides & Catecholamines
- Minutes to an hour
- Steroids (bound to carrier)
- Hours to days
