3. rebsorption in the kidney (renal tubules) and exretion by the kidney as well
T/F: Renal reabsorption of calcium in the kidney is not efficient.
False; it is very efficient
T/F: the extracellular fluid pool of calcium turns over a lot of calcium in a day (40-50 times a day).
True
What is the cause of kidney stones?
The reabsorption of calcium in the kidney can decrease in hypercalcemia in order to help get rid of calcium, but it can't do enough, so you get kidney stones
Which bone cells help to make the osteoid?
osteoblasts
An organic matrix composed of collagen fibers is the ____?
osteoid
Calcium phosphate occurs in the form of submicroscopic crystals called ________ that deposit on the osteoid.
hydroxyapatite
Where does the exchange of calcium occur in bones?
between the surface of the crystals and the extracellular fluid
T/F: the exchange of calcium is inversely proportional to crystal size.
true; as crystal gets smaller (as we age), the more calcium that is deposited and this might be related to osteoporosis
T/F: 99% of bone calcium phosphate is found in large, non-exchangeable or diffusion-locked crystals
true!
What are odontoblasts?
osteoblasts responsible for bone formation in the teeth
Which bone cells are responsible for bone formation?
osteoBlasts
blast=build
Which bone cells synthesize osteoid on which apatite formation occurs?
osteoblasts
T/F: osteoblast are multinucleate?
false
_______ comprise endosteal membrane that lines cavities within bone?
osteoblasts
_______ are the bone cells responsible for bone reabsorption (destroying bone)?
osteoclasts
T/F: osteocytes are also uninucleate.
true
Which bone cells are multinucleate?
osteoclasts
What are the 3 hormones mainly responsible for maintaining calcium and phosphorous homeostasis?
1. vitamin D3
2. calcitonin
3. parathyroid hormone
Which bone related hormone is a secosteroid?
vitamin D3
Where is vitamin D3 made?
all throughout the body
Where is calcitonin made?
the parafollicular cells of the THyroid gland
Where is parathyroid hormone made?
parathyroid glands
The TSH receptor activates which 2 pathways?
IP3 pathway
cAMP pathway
Elevated PKC and PKA levels increase the synthesis of what 4 things important in the thyroid pathway?
Na-I Symporter
H2O2 production
TPO production
uptake of colloid droplets
T/F: both Hashimoto's and Grave's disease are autoimmune diseases.
True
What is another name for cholecalciferol?
vitamin D3
What are the 2 reasons why people of African heritage have an increased incidence of Rickett's?
they produce less vitamin D3 in their skin
they are lactose intolerant
T/F: Vitamin D3 is active.
False
What is another name for calcitrol?
1,25(OH)2D3 (the active form of vitamin D after all conversions)
T/F: We need UVA sun rays to get Vitamin D.
False; UVB
Why do we not get enough Vitamin D from the sun?
Because most of the sun present all day long is UVA and we actually need UVB, which is related to the angle of the rays. Therefore we just do not get enough, especially in WY
Calcium uptake in the intestines is dependent on which protein?
calbindin
1,25 VitaminD3 stimulates the synthesis of what 2 things?
calbindin
Calcium activated ATPase
T/F: calcium concentrations in the intestine increase when calcium binds to calbindin.
False
Where are the receptors for Vitamin D?
in the nucleus because it is a steroid
Which hormone stimylates cartilage and bone growth?
growth hormone
Which hormone has permissive effects on growth hormone secretion and action?
thyroid hormone
T/F: being deficient in thyroid hormone could potentially cause a person to be short.
true
_____ ______ ______ are mediators of growth hormone action on osteoblasts?
IGFs (insulin-like growth factors)
High levels of _________stimulate PTH release, causing an increase in bone reabsorption and hypercalcemia?
glucocorticoids like cortisol
_______ block further growth of long bones, protect the adult skeleton from reabsorption, may reduce PTH release and prevent hypercalcemia, and effect the closure of the epiphyseal plate?
Estrogens/androgens
____ can prevent osteoporosis after menopause, but may in turn cause stroke?
estrogen/androgens
T/F: calcitonin is secreted by the parathyroid gland.
False
_______ is secreted by the parafollicular or C cells of the thyroid gland?
calcitonin
Which hormone is a hypocalcemic factor?
calcitonin
Which hormone causes a decrease in plasma calcium levels?
calcitonin
How does calcitonin lower plasma calcium levels? (2 ways)
inhibits osteoclasts
antagonizes the actions of PTH on bone (not kidney)
T/F: the parathyroid glands directly sense the level of calcium in the blood.
true
What are the two types of Parathyroid cells?
Chief cells (99%)
Oxyphil cells (fewer)
Which hormone is a hypercalcemic factor?
parathyroid hormone
Which hormone causes an elevation in plasma calcium levels?
PTH
How does PTH elevate plasma calcium levels?
by activating osteoclasts (indirectly) by osteoblasts responding to PTH and then secreting OAF, which activates osteoclasts, which then pull calcium out of bones and into the blood
What is another way that PTH increases plasma calcium levels?
by increasing calcium reabsorption in the ascending loop of Henle and distal convoluted tubule
-does this by increasing the uptake of calcium ATPase and the Na-Ca antiporter
PTH also indirectly increases calcium uptake in the intestines by doing what?
increasin 1,25D3 production in the kidney by stimulating 1-hydroxylase synthesis
What is required for PTH to act on bone?
1,25D3
If calcium blood levels are low, what hormone will be secreted?
PTH
If calcium blood levels are high, what hormone will be secreted and what hormone will be inhibited?
calcitonin released, PTH inhibited
What is the main cause of hypercalcemia in hospitalized patients?
cancer
How does cancer cause hypercalcemia?
PTHrp (PTH related peptide)
OAF (osteoClast act. factor)
What hormone is made in the alpha cells of the pancreas?
glucagon
What hormone is made in the beta cells of the pancreas?
insulin
What hormone is made in the delta cells of the pancreas?
somatostatin
What is the signal transduction mechanism for estrogen, a steroid hormone?
altering transcription of mRNA
Which portion of the pituitary gland produces MSH?
Pars Intermedia of the anterior pit
T/F: The pars tuberalis produces hormones.
False
What hormones does the pars nervosa produce?
oxytoxin
vasopressin (ADH)
What is the rate limiting enzyme of melatonin synthesis?
N-acetyltransferase (NAT)
What would happen if you were in constant darkness for several days?
melatonin would still follow a circadian rhythm of about 25 hours
If the PVN is destroyed, what will be the result?
melatonin not secreted at all during a 24 hour period, but the SCN and eye are still functioning so the activity levels do not change
What will be the result if the optic tract is severed?
object will free run and if the periodicity is 25 hours, the actogram will shift 1 hour to the right every day
What will be the result if the SCN is severed or lesioned?
activity is completely random, no periodicity at all
In females, what ducts atrophy as a result of apoptosis?
Wolffian
Androgens (testosterone) is made by what cells in males?
Leydig
Which cells secrete inhibin in the male?
Sertoli cells
Where are sperm produced?
seminiferous tubules
Where are sperm stored?
epidydimal ducts
Which hormone in the female increases a lot right before ovulation?
estrogen
Which enzyme converts Testosterone to DHT?
5-alpha-reductase
T/F: estrogen production in the follicles is controlled exclusively by LH.
False; also fSH
T/F: Estrogen production in the ovarian follicles involves both thecal and granulosa cells.
True
Which hormone do aromatase and 5-alpha reductase act on?
testosterone
T/F: Testosterone causes breast development in XY females.
False; huge amounts of estrogen does
T/F: Collagenase is secreted by the primordial follicle.
False; only the mature follicle
T/F: LH and FSH are secreted by the same cells.
true; in the ant. pit
T/F: LH and FSH act on the same cells.
false
Which cells in the female are located on the very outer edge of the follicle?
thecal cells
What hormone acts on the thecal cells?
LH
What does LH act to do in the thecal cells?
LH stimulates production of testosterone
Which cells are located in the inner layer of the follicle?
granulosa cells
What hormone acts on the granulosa cells?
FSH
What does FSH act to do in the granulosa cells?
FSH converts testosterone to estrogen
Which hormone stimulates the release of GnRH and is implicated in reproduction/the onset of puberty?
kisspeptin
Explain how it is possible for an XY individual to have XX genitalia?
they are androgen insensitive
they can't produce androgens
they have testes, but no penis or scrotum
they do not have a Wolffian duct
they do not have a Mullerian duct
they have a vagina that is a dead end
Explain how the genitalia of a male fetus develops.
1. SRY gene produces TDF
2. Leydig cells produce Testosterone and MIH
3. Testosterone is converted to DHT by 5-alpha-reductase
4. DHT forms the penis and the scrotum
Explain how it is possible for an XX individual to have XY genitalia.
**Congenital Adrenal Hyperplasia**
the enzyme for producing cortisol is absent so you get overproduction of androgens
no Wolffian duct
lots of Testosterone
large clitoris
intact Mullerian duct
behave like a male
salt wasting pathology
What is the disease marked by high cortisol level?
Cushing's
What is the disease marked by low cortisol levels?
Addison's
What is the disease marked by high TH levels and is autoimmune?
Grave's
What is the disease marked by low TH levels and is autoimmune?
Hashimoto's
What is the disease marked by actual removal of the adrenal glands and therefore low cortisol levels?
Nelson's
T/F: thyroid hormones are water-soluble.
false
T/F: T3 (tri-iodothyronine) has a strong stimulatory effect on TRH secretion.
False
T/F: low cortisol levels cause skin discoloration in Addison's disease.
True
T/F: excess cortisol levels cause skin discoloration in Addison's disease.
False
What are 3 potential causes of goiter?
high iodine levels/increased iodine demand
iodine deficiency
selenium deficiency
Which is more active, T3 or T4?
T3
Which is made in more amounts in our bodies, T3 or T4?
T4 (thyroxine)
T/F: Selenium is an essential element involved in thyroid hormone metabolism.
True
What ion is actively exchanged for iodine at the luminal surface of the follicular cell in the thyroid gland?
Sodium (Na-I symporter)
T/F: Cortisol ameliorates diabetes mellitus.
False; it aggravates it by increasing blood glucose
T/F: Cortisol has an affinity for the aldosterone receptor equal to that of aldosterone.
True
T/F: Eating too much licorice can cause high blood pressure due to an increase in sodium levels.
True
T/F: Cortisol is synthesized from cholesterol and pregnenolone.
True
Angiotensinogen is converted to angiotensin by ______?
renin
Angiotensin I is converted to Angiotensin II by ______?
