5. Endocrine System Flashcards
What are 3 types of hormones based on structure?
Peptide, steroids, amino acid derivative (tyrosine)
Peptide hormones (end in -in or -ine) in terms of solubility, duration of effect, location of their receptors, signaling. What other subgroup of hormones that have same properties?
Peptide hormones are water-soluble –> go directly into bloodstream to target tissue; extracellular receptors since they’re charged and can’t cross cell membrane; they’re first messengers and when they reach to their receptors, second messengers act –> rapid effect; cascade signaling. Catecholamines like nor/epinephrine (amino acid derivatives)
What are some common second messengers? How is cAMP regulated?
Cyclic adenosine monophosphate (cAMP), inositol triphosphate (IP3), calcium. Peptide hormone binds to receptor that triggers adenylate cyclase that regulates cAMP levels
Steroid hormones (end in -one, -ol, or -oid) in terms of solubility, duration of effect, location of their receptors, signaling
Steroid hormones are lipid-soluble –> need carrier proteins to go to target tissue, if bound to carrier proteins the steroid hormones are inactive –> carrier proteins can determine active levels of hormones and trick the body; intracellular receptors since they can cross the cell membrane due to lipid solubility; they deal with gene regulation (transcription/translation) –> long effect; not a cascade, conformational changes (dimerization)
Direct hormones vs tropic hormones. What are examples?
Secreted and act directly on target tissue vs require an immediary to act (they act on other glands to secrete that glands’ hormones). Ex: FSH, LH, ACTH, TSH (tropic) and prolactin, endorphins, GH (direct)
Where do tropic hormones originate? What is an example of a tropic hormone?
Brain and anterior pituitary gland. Ex: GnRH, FSH, LH
What are hormones?
Signaling molecules secreted from glands into bloodstream to target tissues
What’s the alternative name of pituitary? Anterior pituitary? What type of tissue is anterior pituitary made of?
hypophysis. Adenohypophysis. Glandular tissue
Remember the mechanisms of GnRH, CRH, GHRH, PIF
GnRH from hypothalamus –> stimulates anterior pituitary to release FSH/LH –> FSH/LH go to gonads –> gonads release their hormones. CRH from hypothalamus –> stimulates anterior pituitary to release ACTH –> go to adrenal glands –> adrenal glands release their hormones. GHRH from hypothalamus –> anterior pituitary releases GH –> stimulates growth of bones and muscle. PIF = always from hypothalamus –> no prolactin; if hypothalamus stops releasing PIF –> anterior pituitary releases prolactin –> milk PRODUCTION in mammary glands of moms
How does hypothalamus communicate with anterior and posterior pituitary gland?
Anterior via hypophyseal portal system. Posterior via pituitary stock
What hormones are RELEASED from posterior pituitary gland?
Antidiuretic hormone (ADH) for inc reabsorption of water in collecting ducts of kidneys --> CAN CHANGE BLOOD OSMOLARITY, inc plasma osmolarity, inc solute conc in blood. Oxytocin for uterine contractions and milk SECRETION/LETDOWN during lactation in women and bonding THESE HORMONES ARE MADE IN HYPOTHALAMUS BUT SECRETED BY POST PIT
Understand negative feedback loops and give examples
One of the ways hormone conc is controlled. Hypothalamus releases TRH –> TRH stimulates pituitary to release TSH –> TSH stimulates thyroid glands to release T3 (triiodo…) and thyroxine –> thyroid hormones go thru all over body to their receptors; some receptors are found on hypothalamus and pituitary –> when bound, hypothalamus and pituitary stop making hormones. Hypothalamus releases CRF –> CRF stimulates anterior pituitary to release ACTH –> ACTH stimulates adrenal cortex to release cortisol –> cortisol goes to their receptors, too much cortisol goes to anterior pituitary and hypothalamus
What are 3-organ systems called?
Axes
What is acromegaly? Which hormones causes this?
Enlargement of hands, feet and head. GH is active for smaller bones if large bones don’t grow anymore
Understand positive feedback loops and give examples
Release of oxytocin causes uterine contractions –> contractions promote release of oxytocin –> stronger uterine contractions –> more oxytocin, stronger contractions etc. Fevers
What are the 2 major functions of thyroid gland and how are they mediated?
Regulate basal metabolic rate via T3 and T4; promotes calcium homeostasis via calcitonin
How are T3 and T4 produced? Describe regulation of T3 and T4
Iodination of amino acid tyrosine in follicular cells. 3 and 4 refer to number of iodine atoms attached to tyrosine
Increased T3 and T4 –> increased cell respiration, faster degradation of fatty acid and protein synthesis. Negative feedback dec excretion of T3 and T4
How is calcitonin produced?
C-cells aka parafollicular cells in thyroid produce calcitonin in response to high Ca levels in blood to tone down calcium levels in blood via inc Ca excretion from kidneys, inc Ca storage in bone, and dec Ca absorption in gut
What does parathyroid gland do?
Produce parathyroid hormone (PTH); does the exact opposite of calcitonin: raises Ca levels via dec Ca excretion from kidneys, inc Ca resorption in bone, inc Ca absorption in gut. Also does phosphorous homeostasis. And it activates vitamin D, which promotes Ca and phosphorous homeostasis
What is the adrenal cortex? What does it secrete?
Part of adrenal gland that secretes corticosteroids of 3 types: glucocorticoids, mineralocorticoids, cortical sex hormones (these are all steroid hormones)
What are glucocorticoids? Examples?
Regulate glucose levels by inc gluconeogenesis and dec protein synthesis. Controlled by ACTH. Ex: cortisol, cortisone
What are mineralocorticoids? Examples?
Regulate salt and water homeostasis by inc Na & H2O reabsorption in distal tubule and collecting ducts of kidneys and promotes urine excretion. Ex: aldosterone
How is aldosterone secreted?
Under renin-angiotensin-aldosterone system: low bp –> macula densa stimulate juxtaglomerular cells to dilate afferent arteriole —> secrete renin –> renin cleaves inactive plasma protein angiotensinogen into active angiotensin I –> angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II –> angiotensin II stimulates adrenal cortex to secrete aldosterone —> aldosterone acts on distal nephrons —> inc Na+ reabsorption, inc K+ and H+ excretion. When bp = nml –> neg feedback for renin release. Aldosterone has nothing to do with hematocrit, does not change blood osmolarity
What are cortical sex hormones? Examples?
Determine sex. Ex: androgens (male) and estrogen (female)
What is the adrenal medulla? What does it secrete?
Part of adrenal gland that secretes nor/epinephrine. These hormones result in inc vasodilation, heart rate, bloodflow. Epinephrine for short term stress response, cortisol for long term stress response
How does pancreas secrete hormones?
Islets of Langerhans have alpha cells secreting glucagon, beta cells secreting insulin, and delta cells secreting somatostatin
What does glucagon do?
This hormone is secreted when glucose is gone –> inc gluconeogenesis, protein and fat degradation
What does insulin do?
This hormone does opposite of glucagon –> promotes muscle and liver cells to absorb glucose and store as glycogen. Too much insulin can cause hypoglycemia (low blood glucose); too low insulin can cause hyperglycemia (high blood glucose) => DM. Diabetics experience polyuria and polydipsia
Type I vs Type II DM
IDDM, autoimmune B cells results in no insulin production vs NIDDM low receptor activation by insulin
What does somatostatin do?
inhibitor of both insulin and glucagon secretion during times of high blood glucose and protein. Also dec GH
What do gonads do?
Testes secrete testosterone in response to gonadotropins (FSH/LH), ovaries secrete estrogen and progesterone in response to gonadotropins
What does the pineal gland do?
Secretes melantonin to regulate circadian rhythms
Which other organs secrete hormones?
Kidneys secrete erythropoietin to stimulate bone marrow to inc production of erythrocytes (RBC) in response to low oxygen in blood. Heart secretes atrial natriuretic peptide (ANP) to regulate salt and water balance in response to excess blood volume and high bp, dilates afferent arteriole. Thymus secretes thymosin for T-cell development. Liver release insulin-like growth factors in response to GH
Endocrine vs exocrine
Release substances into bloodstream vs release substances onto epithelial surface
How do pancreas and liver act as exocrine organs?
Both secrete enzymes to aid digestion
How do dopamine and prolactin relate?
Dopamine secretion prevents prolactin release
3 types of hormone release
Humoral (bloodstream), hormonal, and neural stimulation
