Lecture 61 - Endocrine 3

Question 1

what are the 4 functions of calcium?

Answer 1

1. bone and teeth structure
2. muscle function
3. nerve transmission
4. hemostasis

Question 2

what two blood tubes contain chelating agents? What does this mean?

Answer 2

purple top (EDTA) and blue top (citrate)

chelate calcium so clots are unable to form

Question 3

what role does calcium play in protein hormone synthesis

Answer 3

exocytosis - helps secretory vesicles bind with the plasma membrane

Question 4

Ionized calcium

Answer 4

non-protein bound (biologically active)

Question 5

total calcium

Answer 5

ionized and protein-bound calcium (albumin)

Question 6

what are the 5 functions of phosphate

Answer 6

1. bone and teeth structure
2. muscle function
3. acid-base balance
4. energy provision
5. nucleic acids

Question 7

inorganic phosphate

Answer 7

simple form found in bone and teeth

Question 8

organic phosphate

Answer 8

contain phosphate and carbon
found in ATP, DNA, etc.

Question 9

T/F: protein-bound Ca is biologically active

Answer 9

FALSE

Question 10

what is the distribution of calcium in the body? list from most stores to the least

Answer 10

1. hydroxyapatite in bone
2. intracellular
3. extracellular

Question 11

what are the 3 hormones involved in calcium homeostasis

Answer 11

1. parathyroid hormone
2. calcitonin
3. vitamin D

Question 12

what 3 organs play a role in calcium homeostasis

Answer 12

1. bone (reservoir)
2. GI (in)
3. kidneys (out)

Question 13

the parathyroid hormone works to

Answer 13

increase calcium

Question 14

how does PTH increase blood calcium

Answer 14

increase resorption by kidneys, stimulate release from bone

Question 15

summarize vitamin D metabolism in 5 steps

Answer 15

1. UVB hits skin
2. supports conversion of pre-vitamin D to vitamin D3
3. vitamin D3 hydroxylated in the liver
4. 25-hydroxyvitamin D (calcidiol) hydroxylated in the kidneys
5. 1,25-hydroxyvitamin D (calcitriol) is ACTIVE

Question 16

what enzyme coverts calcidiol to calcitriol

Answer 16

1a-hydroxylase

Question 17

PTH ____ the activity of 1a-hydroxylase

Answer 17

increases

Question 18

PTH ____ tubular resorption of calcium

Answer 18

increases

Question 19

PTH ____ tubular resorption of phosphate

Answer 19

decreases

Question 20

what two hormones increase osteoclastic activity

Answer 20

PTH and calcitriol

Question 21

describe how metabolic bone disease correlates to calcium homeostasis

Answer 21

• inappropriate diet (low Ca/high P)
• bone resorption and production of fibrous tissue (swollen, weak bones)

Question 22

an 8y/o castrated male labrador comes into the clinic with PU/PD. Diagnostic tests identify high calcium and low phosphate. what may cause this?

Answer 22

primary hyperparathyroidism (excessive PTH from mass continues to raise calcium)

Question 23

what is the function of calcitonin

Answer 23

1. functionally oppose PTH
2. decrease bone resorption and osteoclastic activity
3. increased renal excretion of Ca and P

Question 24

calcitonin ___ blood calcium

Answer 24

decreases

Question 25

what effect does PTH have on Ca and P?

Answer 25

increase Ca and decrease P

Question 26

T/F: PTH enhances P loss via the kidney

Answer 26

TRUE

Question 27

what produces calcitonin

Answer 27

parafollicular ("C") cells

Question 28

what do "C" cells look like on histology

Answer 28

pale staining, large ovoid nuclei

Question 29

calcitonin exerts its effect mostly by affecting which organ

Answer 29

bone

Question 30

which hormone would increase in a cow with mild fever (hypocalcemic tetany)?

Answer 30

PTH

Question 31

what are the 3 steps to protein-based hormone synthesis

Answer 31

1. synthesis (pre-pro-) 2. packaging (pro-) 3. storage (target hormone)