Introduction to Endocrine System (Creamer) Flashcards
What is autocrine signaling?
Cell secretes a hormone or chemical messenger that binds to self receptors
What is paracrine signaling?
Cell produces a hormone or chemical messenger to induce changes in nearby cells
What is endocrine signaling?
A cell targets a distant cell through the bloodstream. A signaling molecule is released by one cell, then travels through the bloodstream to bind to receptors on a distant target cell elsewhere in the body.
What is neuroendocrine signaling?
Release of a hormone from a nerve cell, typically into the bloodstream, which will have an effect on a cell in the periphery.
What hormones are released from the hypothalamus?
TRH, CRH, GnRH, PIF, GHRH, Somatostasin, Oxytocin, ADH
What hormones are released from the anterior pituitary?
FSH/LH
ACTH
TSH
Prolactin
Endorphins
GH
FLAT PEG
What hormones are released from the posterior pituitary?
Oxytocin & ADH (Vasopressin)
What hormones are released from the thyroid?
T3, T4 &Calcitonin
What hormones are released from the parathyroid?
PTH
What hormones are released from the pancrease?
Insulin & Glucagon
What hormones are released from the adrenal medulla?
Norepinephrine & Epinephrine
What hormones are released from the kidney?
Renin & Calcitriol
What hormones are released from the adrenal cortex?
Cortisol
Aldosterone
Adrenal Androgens
What hormones are released from the testes?
Androgens (especially testosterone) & inhibin
What hormones are released from the ovaries?
Estradiol
Progesterone
What hormones are released from the corpus luteum?
Estradiol
Progesterone
What hormones are released from the placenta?
HCG
Estriol
Progesterone
hPL
What are the three general classes of hormones?
Protein/peptide
Steroid
Amines
Peptide hormones
- Synthesis
- Secretion
- Do they bind to circulating proteins
- Halflife & clearance
- Synthesized from preprohormone
- Stored in secretory vesicles in the cell of endocrine gland where they are released once gland is stimulated
- Very little
- Short half life & rapid metabolic clearance
Steroid hormones
- Synthesis
- Secretion
- Do they bind to circulating proteins
- Halflife & clearance
- Synthesized from cholesterol
- Lipid soluble so they diffuse through cell
- Yes
- > proteins, < amines & slower metabolic clearance rate
What glands synthesize and secretes steroid hormones?
Adrenal Cortex
Gonads
Corpus Luteum
Placenta
What are the two types of endocrine amines and what are they derived from?
Catecholamines & Thyroid hormones
Tyrosine
Catecholamine hormones
- Synthesis
- Secretion
- Do they bind to circulating proteins
- Halflife & clearance
- Synthesized in cytosol
- Act through cell-membrane associated receptors
- Yes
- Longest half life and have very slow metabolic clearance rates
Thyroid hormones
- Synthesis
- Secretion
- Do they bind to circulating proteins
- Halflife & clearance
- Synthesized and stored in thyroid gland
- Secrete through follicles and act through Nuclear receptors
- Yes
- Longest half life and slowest metabolic clearance rate
If a hormone has a high protein binding rate, does it have a slow or fast metabolic clearing rate?
Slow (Long-acting)
What is positive feedback?
- Positive feedback is a process in which the end products of an action cause more of that action to occur in a feedback loop. This amplifies the original action
What is an example of positive feedback?
Ovulation
Labor Contractions
What is negative feedback?
Occurs when high level of a particular hormone inhibits further secretion of that hormone, or where the result of a certain action may inhibit further performance of that action.
What is an example of major endocrine axes?
Hypothalamus –> Anterior Pituitary —>Target Tissue
What is the first tier of the endocrine axes?
Hypothalamus
How is the first tier (hypothalamus) of the endocrine axes regulated
It is regulates at the level of neural input. Example is the Suprachiamatuc nucleus (SCN)
What is the function of the suprachiasmatic nucleus (SCN)?
Impose a circadian rhythm
What is the function of the pineal gland?
Release melatonin which influences SCN on day/night cycle
What is up-regulation?
Increase number of receptors or sensitivity of target tissue when hormone levels are low
What are ways to cause up-regulation?
Increase synthesis of new receptors
Decrease the rate of degradation of existing receptors
Activate current receptors
What is down-regulation?
Reducing number of receptors or sensitivity of target tissue when hormone levels are high
What are ways to cause down-regulation?
Decrease receptor synthesis
Increase the rate of degradation of existing receptors
Deactivate current receptors
What are the major mechanisms of hormone action on target cells
- Adenylyl cyclase
- Phospholipase C
- Steroid hormone
- Guanylyl cyclase
- Tyrosine kinase
What is the Adenylyl cyclase mechanism
GPCR
1st messenger: hormone
Primary effector: adenylyl cyclase
2nd messenger: cAMP –> 5’ AMP
Secondary effector: Protein Kinase A
What hormones use the adenylyl cyclase mechanism
ACTH
LH
FSH
TSH
What is the Phospholipase C mechanism
GPCR
1st messenger: hormone
Primary effector: Phospholipase C
2nd messenger: IP3/DAG/Ca2+
Secondary effectpr: PKC or calmodulin
What hormones use the Phospholipase C mechanism
GnRH, TRH & oxytocin
How do steroid hormones work?
After steroid hormones bind to cytosol/nuclear receptors, the complex binds to DNA to activate certain genes to produce new protein (hormone).
What hormones use the steroid hormone mechanism
Glucocorticoids
Estrogen
Progesterone
Testosterone
Aldosterone
Thyroid hormones
What is the Guanylyl cyclase mechanism
Conversion of GTP to cGMP. cGMP activates cGMP kinase resulting in the relaxation of smooth muscles
What hormones use the guanylyl cyclase mechanism
Atrial natriuretic peptide (ANP)
Nitric Oxide (NO)
What do the tyrosine kinase receptors do
When activated they phosphorylate downstream proteins
What hormones use the Tyrosine kinases mechanism
Insulin
Growth hormone
Prolactin