26 terms

MCAT - Chap 5 - Endocrine System

General hormones (as opposed to local hormones)
released into the blood stream instead of hitting specific tissues
Exocrine glands do what?
Release enzymes to the external environment
-sudoriferous (sweat)
-sebaceous (oil)
-and digestive
Endocrine glands do what?
Release hormones directly into body fluids
Three basic chemistry types of hormones
1. peptide hormones
2. steroid hormones
3. tyrosine derivatives
Peptide hormones (characteristics)
-derived from peptides
-water-soluable (travel freely in blood, not so freely through lipid bilayers of cells/effectors/target cells)
-these guys NEED receptors
Important types of peptide hormones (4)
1. anterior pituitary hormones: FSH, LH, ACTH, hGH, TSH, Prolactin
2. posterior pituitary hormones: ADH and oxytocin
3. parathyroid hormone: PTH
4. pancreatic hormones: glucagon and insulin
Steroid hormones (characteristics)
-derived from cholesterol
-lipids, require protein transport molecule to get through the blood
-usually acts at the transcription level (usually to bump up production of membrane or cellular proteins within the effector)
Important types of steroid hormones (2)
1. glucocorticoids and mineral corticoids of the adrenal cortex (cortisol and aldosterone)
2. gonadal hormones: estrogen, progesterone, testosterone
Tyrosine derivatives (characteristics)
-some membrane-crossing (thyroids), some not able to cross membrane (catecholamines)
-formed in the cytosol or on the rough ER
Important types of tyrosine hormones (2)
1. thyroid hormones (T3 and T4) --> crossers
2. catecholamines formed in the adrenal medulla (epinephrine and norepinephrine) --> signalers
What does ADH do?
-decrease urine output
-increase blood pressure
always digging holes...to keep water in? in your body?
What comes from the anterior pituitary?
1. human growth hormone (hGH)
2. adrenocorticotropin (ACTH)
3. thyroid-stimulating hormone (TSH)
4. follicle-stimulating hormone (FSH)
5. leutenizing hormone (LH)
6. prolactin

--> ALL peptide hormones
Human growth hormone (hGH)
-no specific target cells
-stimulates growth in pretty much everything
-increases transcription and translation
Adrenocorticotropin (ACTH)
stimulates adrenal cortex --> to release glucocorticoids

--> implicated in stress
Thyroid-stimulating hormone (TSH)
stimulates thyroid to release T3 and T4
--> T3 and T4 then have a negative feedback loop effect on both the hypothalamus and the pituitary gland
FSH and LH (follicle-stimulating and lutenizing hormone) ?
all for reproduction business, that's some complicated **** right there
promotes lactation by the breasts

--> before birth, progesterone and estrogen inhibit milk production
Onwards, to the posterior pituitary gland, it releases two types of hormones
1. oxytocin
2. Anti-diuretic hormone (ADH)
-increases uterine contractions during pregnancy
-causes milk to be ejected from breast
-aka vasopressin
-alcohol is an ADH blocker, which is why it increases urine output
Adrenal GlandSSS
1. Adrenal cortex
2. adrenal medulla

--> right above the kidneys
Adrenal Cortex contains what?

Remember: cortex = steroids
1. aldosterone: Na+ absorption, K+ secretion in the kidney
2. cortisol: increases blood glucose levels by stimulating the liver
--> both are steroids
Adrenal Medulla contains what?

Remember: medulla = tyrosine
1) epinephrine:
2) norepinephrine
--> both fight-or-flight hormones
constrict bloodflow to internal organs, encourage bloodflow to skeletal muscles
What does the thyroid release?

Thyroid = tyrosine

Thyroid is also the only one that releases two different types of hormones (tyrosine and peptide)
1) T3 and T4 (lipid soluble) --> increase basal metabolic rate
2) Calcitonin: peptide hormone
--> decreases blood calcium by decreasing osteoclast activity
What does the pancreas release?

Remember: pancreas both endocrine and exocrine gland --> peptide hormones only
1) insulin: lowers blood glucose (pack it on the cells!)
--> cells of the body become highly permeable when bound to insulin
2) glucagon: opposite of insulin
---> breaks down adipose tissues, increases levels of fatty acids in the blood, RAISES blood glucose levels
What does the parathyroid do?
releases parathryoid hormone (wow.)
-peptide, increases blood calcium