Lecture 8: Introduction to Endocrine System 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?
Feedback loops of hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs
What is neuroendocrine signaling?
Release of a hormone from a nerve cell that has an effect on another cell
What hormones are released from the hypothalamus?
TRH CRH GnRH GHRH Somatostatin Dopamine
What hormones are released from the anterior pituitary?
FSH LH ACTH TSH MSH Prolactin Growth Hormone
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?
Testosterone
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 type of hormones?
Protein/peptide
Steroid
Amines
What are characteristics of peptide hormones?
Synthesized from preprohormone
Stored in secretory vesicles
Water soluble
Membrane receptors
What are characteristics of steroid hormones?
Synthesized from cholesterol
Lipid soluble
Cytosol or nuclear receptors
What synthesizes and secretes steroid hormones?
Adrenal Cortex
Gonads
Corpus Luteum
Placenta
What are amines derived from?
Tyrosine
What are catecholamines?
Synthesized in cytosol
Cell-membrane associated receptors
What are thyroid hormones?
Synthesized and stored in thyroid gland
Nuclear receptors
If a hormone has a high protein binding rate, does it have a slow slow or fast metabolic clearing rate?
Slow (Long-acting)
What is an example of hormone secretion via neural mechanism?
Sympathetic preganglionic innervation of adrenal medulla to release catecholamines
What is positive feedback?
Hormones continue to secrete other hormones, amplifying its effect greatly
Not common
Where is positive feedback found?
Ovulation
Labor Contractions
What is negative feedback?
Hormone secretion will inhibit or balance other hormones to have controlled effects
What is an example of major endocrine axes?
Hypothalamus –> Anterior Pituitary —>Target Tissue
What is the first tier of the endocrine axes?
Hypothalamus
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?
Reduce number of receptors or sensitivity or 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 different pathways do GPCR receptors activate?
1) Adenylyl cyclase and cAMP
2) Phospholipase C and IP3/DAG/Ca2+
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 happens when cGMP kinases are activated?
Relaxation of vascular smooth muscles (NO)
