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
What hormones are secreted by which parts of the adrenal glands?
Adrenal cortex secretes corticosteroids
Adrenal medulla secretes epinephrine and norepinephrine
What are glucocorticoids?
steroid hormones that regulate glucose levels
What are mineralcorticoids?
steroid hormones that control salt and water homeostasis
What is the renin-angiotensin-aldosterone system?
Triggered by decreased blood pressure.
(1) Juxtaglomercular cells of the kidney secrete renin
(2) Renin cleaves inactive protein angiotensinogen
(3) Now we have active Angiotensin I
(4) Angiotensin I gets converted to Angiotensin II by ACE (angiotensin-coverting enzyme)
(5) Angiotensin II stimulates adrenal cortex to release aldosterone
(6) Blood pressure gets stabilized and renin production decreases
What are corticol sex hormones?
hormones that control sex production stuff - androgens and estrogens
What is the hypothalamic negative feedback mechanism?
The hypothalamus secreted corticotropin-releasing factor (CRF) which stimulates the anterior pituitary to secrete adrenocorticotropic hormone (ACTH). This causes the adrenal cortex to secrete cortisol. Cortisol blocks the ability of the anterior pituitary and hypothalamus to secrete ACTH and CRF, respectively.
What is the calcitonin-PTH mechanism?
PTH increases blood calcium levels; as blood calcium levels rise, calcium then (inhibits PTH) promotes calcintonin production which decreases the calcium levels.
What are the cell types of the pancreas and what do they secrete?
alpha - glucagon
beta - insulin
deta - somatostatin
What are islets of Langerhans?
groups of hormone producing cells in the pancreas that contain a combination of alpha, beta, and delta
What is the insulin mechanism?
Eat food
(1) Blood glucose levels go up
(2) Stimulates insulin secretion
(3) Lowers the blood glucose level
(4) Inhibits insulin
(5) Blood glucose begins to rise agai
What is hypoglycemia?
low blood glucose concentration, which can be caused by excess insulin
What is diabetes mellitus?
aka “hyperglycemia” which is when there is a underproduction or insensitivity to insulin
What are the two types of diabetes mellitus?
Type I (insulin dependent) - autoimmune destruction of the beta-cells of the pancreas (so low insulin production) Type II (non-insulin dependent) - due to receptor level resistance to the effects of insulin; partially due to diet and weight
Where is the pineal gland located?
deep within the brain
