The Endocrine System Flashcards
What are hormones?
signaling molecules that are secreted directly into the bloodstream to distant target tissues
What are the types of hormones?
peptides, steroids, amino acid derivatives
Describe peptide hormones
made of amino acids; derived from larger polypeptides that were cleaved during posttranslational modification; they are charged and cannot pass through membranes so they must bind to receptors (first messenger); water soluble and travel in bloodstream without carriers; they work through signaling cascades
Name three common second messengers?
cAMP, inositol triphosphate (IP3) and calcium
Describe steroid hormones
derived from cholesterol and produced primarily by the gonads and adrenal cortex; can easily cross the cell membrane and bind to intracellular receptors which causes a conformational change in the receptor complex so now it can bind to DNA and cause changes in gene regulation; slower but longer lived changes; steroids must be transported by proteins through the bloodstream
How do carrier proteins affect steroid hormones?
they help them transport through the body but make them inactive while attached
Describe amino acid-derivative hormones
less common than peptide and steroid; these are derived from one or two amino acids with modifications
What are four examples of amino acid-derivative hormones?
epinephrine, norepinephrine, triiodothyronine, thyroxine
Direct vs Tropic hormones
Direct hormones are secreted and act directly on the target tissue to change the physiology (like insulin) while tropic hormones use intermediaries; they activate other hormones which then change the physiology and act as direct hormones (like GnRH and LH and FSH)
What hormones does the hypothalamus secrete?
(1) Gonadotropin-releasing hormone (GnRH)
(2) Growth hormone-releasing hormone (GHRH)
(3) Thyroid-releasing hormone (TRH)
(4) Corticotropin-releasing factor (CRF)
(5) Prolactin-inhibiting factor (PIF)
Where is the hypothalamus located?
in the forebrain, directly above the pituitary gland and below the thalamus
What does the hypothalamus do?
connects the nervous and endocrine systems - gets information from the nervous system and controls the hormones the pituitary gland sends out
What is the hypophyseal portal system?
a blood vessel system that directly connects the hypothalamus with the anterior pituitary
What hormones does the posterior pituitary release?
oxytocin and ADH
What hormones are secreted by the anterior pituitary?
FLAT (tropic) PEG (direct) F - FSH L - LH A - ACTH T - TSH P - prolactin E - endorphins G - GH
Where is the thyroid located?
on the front surface of the trachea; butterfly shaped
What is the thyroid’s function?
(1) set the basal metabolic rate
(2) promote calcium homeostasis
What hormones does the thyroid release?
triiodothryonine and thyroxine and calcitonin
What is hypothyroidism?
when thyroid hormones are secreted in insufficient amounts due to a deficiency in iodine or inflammation ; lethargy, decreased body temp, slowed respiratory and heart rate, cold intolerance and weight gain
What is hyperthyroidism?
when thyroid hormones are oversecreted; heightened activity level, increased body temp, increased respiratory and heart rate, heat intolerance and weight loss
What two types of cell is the thyroid made up of?
Follicular cells - produce thyroid hormones
C-cells - produce calcitonin
Where are the parathyroid glands located?
four small pea sized structures that sit on the posterior surface of the thyroid
What hormone does the parathyroid glands secrete?
PTH - parathyroid hormone
Where are the adrenal glands located?
on top of the kidneys
