Lecture 17 - Ca & PO4

Question 1

plasma calcium is regulated by

Answer 1

parathyroid hormone (PTH)
vitamin D

Question 2

calcium can bind to

Answer 2

nerve axons - affecting action potential frequency

Question 3

when plasma acidosis occurs, there are less Ca than H bound to albumin

Answer 3

increase free Ca on the nerve axon
decrease # of neuronal AP
decrease muscle contraction
WEAKNESS

Question 4

when plasma alkalosis occurs, there are more Ca than H bound to albumin

Answer 4

decrease free Ca on the nerve axon
increase # of neuronal AP
increase muscle contraction
twitching

Question 5

hypocelcemic tetany: carpopedal spasm

Answer 5

hyperventilation
low plasma CO2
respiratory alkalosis
decreased free Ca
increased freq. of motor neuron action potentials
skeletal muscle contraction
tetany

Question 6

physiological role of phosphorus

Answer 6

major intracellular anion, ATP, co-factor, modifies proteins and/or enzyme activity
intracellular buffer in acid-base balance
DNA, RNA, membrane phospholipids

Question 7

bone remodeling

Answer 7

calcified matrix: hydroxyapatite crystals within osteoid
osteoid: collagen-based matrix
resportion = formation (is good)

Question 8

amorphous crystals
1st bone pool

Answer 8

4-5 g
liquid solution on surface of newly formed bone
fast exchange with ECF
osteolysis: initial burst of Ca

Question 9

hydroxyapatite crystals
2nd bone pool

Answer 9

1000 g
mineralized bone
slow exchange with ECF
bone resorption: release Ca and PO4 into plasma

Question 10

osteoblasts

Answer 10

build bone

Question 11

osteocytes

Answer 11

detect worn-out bone

Question 12

osteoclasts

Answer 12

chew up bone

Question 13

PTH stimulates osteoblasts to

Answer 13

secrete M-CSF and osteoprotegerin which can bind to RANKL

secrete collagen and osteocalcin -> osteoid

Question 14

after binding of RANKL and M-CSF,

Answer 14

preosteoclasts mature to osteoclasts (chew)

Question 15

Osteoclasts chew the bone and released

Answer 15

Ca and P enter plasma

Question 16

osteocytes detect worn out bone,

Answer 16

secrete RANKL, and attract osteoclasts

Question 17

PTH favors bone

Answer 17

breakdown

Question 18

Vitamin D favors bone

Answer 18

formation

Question 19

PTH fxn

Answer 19

acute regulation of plasma ionized calcum

Question 20

vitamin D fxn

Answer 20

long-term maintenance of strong bones

Question 21

Calcium sensing receptors (CaSR) on PTH cheif cells sense

Answer 21

extracellular free Ca conc

Question 22

decrease in plasma Ca…

Answer 22

increases plasma PTH

Question 23

plasma Ca primary stimulus

Answer 23

decreased ionized ca stimulates PTH secretion
increased ionized Ca inhibits PTH secretion

Question 24

Lithium stimulates…

Answer 24

PTH secretion: right-shift of curve

Question 25

1,25(OH2)- vitamin D3 inhibits gene expression to

Answer 25

increase synthesis of CaSR decrease synthesis of PTH

Question 26

Vitamin D3 is synthesized from 7-dehydrocholesterole

Answer 26

to previtamin D3

Question 27

melanin can impede converstion because it

Answer 27

absorbs the same uv wavelengths in sunlight

Question 28

previtamin D3 is converted to

Answer 28

Vitamin D3

Question 29

vitamin D3 is converted to

Answer 29

25-OH-vitamin D3 in the liver | amt of vitamin D3 due to diet ## Footnote little biological activity long half-life indicator of vitamin D status synthesis not regulated

Question 30

25-OH-vitamin D3 is converted to

Answer 30

1,25(OH)2-D3 (active) and 24,25-(OH)2-D3 (inactive) in the kidney

Question 31

when converting to 1,25(OH)2-D3 (active)

Answer 31

vitamin D def 1,25(OH)2-D3 def Ca def hypocalcemia increase PTH secretion hypophosphatemia phosphate def

Question 32

when converting 24,25(OH)2D3 (inactive)

Answer 32

vitamin D sufficiency 1,25(OH)2-D3 normocalcemia hypercalcemia normophosphatemia hyperphosphatemia

Question 33

Vitamin D3 physiological effects

Answer 33

increase phosphate absorption and calcium absorption in intestine and Ca and PO4 reabsorption in kidneys the Ca and P go to plasma

Question 34

hormones that favor bone formation and bone mass

Answer 34

insulin GH IGF-1 estrogen testosterone calcitonin

Question 35

hormones that favor increased bone resorption and decreased bone mass

Answer 35

parathyroid hormone plasma cortisol above normal range plama thyroid hormone above normal

Question 36

hyperparathyroidism: due to tumor: high PTH, high Ca, low phosphate due to persistent hypocalcemia: high PTH, low or normal ca, low phosphate

Answer 36

increase bone resportion increase renal Ca reabsorption increase intestinal Ca absorption decrease renal P reabsorption increase urinary Ca and P

Question 37

hyperparathyroidism with chronic renal failure

Answer 37

high PTH and low or normal Ca

Question 38

hypoparathyroidism

Answer 38

1. hypocalcemia: decrease bone resorption decrease renal Ca reabsorption decrease intestinal Ca absorption 2. hyperphosphatemia: increased renal P reabsorption

Question 39

when plasma albumin is above normal range, *plasma free calcium* is

Answer 39

within the normal range

Question 40

when plasma free calcium is below normal range, *plasma free calcium* is

Answer 40

within the normal range

Question 41

when plasma albumin is above the normal range, *plasma total calcium* is

Answer 41

above the normal range

Question 42

when plasma albumin is below the normal range, *plasma total calcium* is

Answer 42

below the normal range