L17

Question 1

Free plasma ___ is a regulated variable controlled by negative feedback loops

Answer 1

calcium

Question 2

Vitamin D is a ___ while PTH is a ____

Answer 2

steroid; peptide

Question 3

What two molecules regulate plasma calcium?

Answer 3

1) PTH
2) Vit D

Question 4

Where in the body does Calcium and PO4 get absorbed in the body?

Answer 4

Intestines

Question 5

Where in the body does filtration and reabsorption of Calcium and PO4 occur?

Answer 5

Kidney

Question 6

Where in the body does resorption and formation of Calcium and PO4 occur?

Answer 6

Bone

Question 7

___: the breakdown and assimilation of old bone in the cycle of bone growth (stealing calcium from the bone)

Answer 7

Resorption

Question 8

____: Storing calcium in bone

Answer 8

Formation

Question 9

Of the total plasma calcium, ___ and ___ are regulated

Answer 9

free calcium; ionized calcium

Question 10

______ calcium can be changed under acid-base disturbances

Answer 10

Free/Ionized calcium
(not 45% of total calcium of total)

Question 11

What does calcium bind to in order to affect action potential frequency?

Answer 11

Ca binds to nerve axons

Question 12

Under acidotic conditions, are more/less calcium molecules bound to albumin?

Are more/less calcium molecules bound to the nerve axons?

Answer 12

Acidotic conditions:
- LESS calcium bound to albumin
- MORE calcium bound to nerve axons

Question 13

Under alkalotic conditions, are there more/less calcium molecules bound to albumin?

Are more/less calcium molecules bound to nerve axons?

Answer 13

Alkalosis:
- MORE calcium bound to albumin
- LESS calcium bound to nerve axons

Question 14

Under what conditions does hypocalcemic tetany occur?

Answer 14

• Hyperventilation (low plasma CO2) = respiratory Alkalosis
• Decreased free calcium
• Increased frequency of motor neuron AP (skeletal muscle contraction)

Question 15

In adults, fatigued or microdamaged bone is replaced by new bone in a continual process called ______

Answer 15

remodeling

Question 16

What are the three stages of remodeling?

Answer 16

1) Resorption: dissolution or removal of bone, ~2 wks

2) Reversal: prepare bone surface for osteoblast attachment, ~4-5 wks

3) Formation: laying down of new bone, ~4 months

Question 17

_____ : small pool of calcium phosphate (Ca)3(HPO4)2 crystals in solution on the surface of new bon

Answer 17

Amorphous crystals

Question 18

What type of crystals are a liquid solution on the surface of newly formed bone and allow for FAST exchange (minutes) of calcium with the extracellular fluid AND transiently buffers ↓/↑ in free ionized calcium via osteolysis?
A. Hydroxyapatite crystals
B. Amorphous crystals

Answer 18

B. Amorphous crystals

Question 19

_____ are large pool of the mineral Ca10(PO4)6(OH)2
interspersed within the osteoid (bone matrix)

This calcium pool ___ exchanges
with the extracellular fluid

Answer 19

Hydroxyapatite crystals

slowly

Question 20

Which crystals allow for bone resorption (releasing Ca/PO4) and makes up mineralized bone?

Answer 20

Hydroxyapatite crystals

Question 21

___ is a bone cell that “cyts” in the bone and detects worn out bone

Answer 21

Osteocytes

Question 22

Answer 22

Question 23

PTH binds to its receptor on an osteoblast, leading to secrete what two molecules?

Answer 23

1) M-CSF
2) OPG (osteoprotegerin)

Question 24

What two molecules bind to RANKL?

Answer 24

M-CSF and OPG

Question 25

RANKL is secreted by____ A. Osteoblast B. Osteoclast C. Osteocyte

Answer 25

C. Osteocyte

Question 26

___ secrete collagen and osteocalcin needed to form the osteoid

Answer 26

Osteoblast

Question 27

What leads the pre-osteoclast to mature into an osteoclast?

Answer 27

Binding of RANKL and M-CSF

Question 28

How do osteoclasts break down bone?

Answer 28

Secrete acids, phosphatase, and enzymes - following this, calcium and phosphate enter into the plasma

Question 29

What are the three roles of osteocytes?

Answer 29

1) Detect worn out bone 2) Secrete RANKL 3) Attract osteoclasts

Question 30

PTH favors ___ of bone while Vit D favors ___ of bone

Answer 30

PTH = breakdown Vit D = formation

Question 31

Which peptide is responsible for acute regulation of plasma ionized calcium? Which molecule is responsible for long-term maintenance of strong bones?

Answer 31

PTH Vit D

Question 32

Which receptors on the parathyroid chief cells sense extracellular calcium levels?

Answer 32

Calcium sensing receptors (CaSR)

Question 33

Under what conditions is parathyroid hormone (PTH) secreted?

Answer 33

Low calcium

Question 34

The normal range of free calcium is the steepest ___ of the curve

Answer 34

Question 35

Why do individuals taking lithium often have greater bone breakdown?

Answer 35

Lithium stimulates PTH secretion and leads to a right shift of the curve - Secretion of PTH even under high calcium conditions

Question 36

1,25 (OH)2-Vitamin D3--the active form of Vitamin D--inhibits gene expression to: 1) Increase synthesis of ____ 2) Decrease synthesis of ____

Answer 36

Increase synthesis of CaSR Decrease synthesis of PTH

Question 37

What is the clinical indicator of Vit D?

Answer 37

25-OH-Vit-D3

Question 38

Where is Vit D3 converted to 25-OH-Vit-D3? Where is 25-OH-Vit-D3 into 1,25-(OH)2-D3 and 24,25-(OH)2-D3?

Answer 38

Liver Kidney

Question 39

Which is the active form of 25-OH-Vit-D3? A.1,25-(OH)2-D3 B. 24,25-(OH)2-D3?

Answer 39

A.1,25-(OH)2-D3

Question 40

Where is pro-vit D made? What is it converted to? What stimulus is required for conversion?

Answer 40

-Dermis -Pre-Vit D -Stimulus: UV Light

Question 41

Previtamin D is slowly (days) converted to ______ by ____ energy.

Answer 41

vitamin D3 (cholecalciferol) thermal energy

Question 42

Vitamin D3 is hydroxylated in the liver to ____

Answer 42

25-OH-vitamin D3

Question 43

What is the major circulating and storage form of vitamin D? A. Pro-Vit D3 B. Pre-Vit D3 C. Cholecalciferol (Vit D3) D. 25-OH-Vit D3 E. 1,25-(OH)2-D3

Answer 43

D. 25-OH-Vit D3 (calcidiol)

Question 44

Where is the Vit D receptor?

Answer 44

On the osteoblast

Question 45

In the kidney, the conversion of 25-OH-Vitamin D to the active ____ by renal ____ is tightly regulated.

Answer 45

1,25-(OH)2- vitamin D 1α hydroxylase

Question 46

Where are Vit D receptors located?

Answer 46

Surface of osteoblast

Question 47

Activation of Vit D will lead to protein synthesis - what two proteins?

Answer 47

1) Osteoid formation 2) Calcium binding protein