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Physiology II > L17 > Flashcards

L17 Flashcards

1
Q

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

A

calcium

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2
Q

Vitamin D is a ___ while PTH is a ____

A

steroid; peptide

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3
Q

What two molecules regulate plasma calcium?

A

1) PTH
2) Vit D

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4
Q

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

A

Intestines

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5
Q

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

A

Kidney

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6
Q

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

A

Bone

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7
Q

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

A

Resorption

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8
Q

____: Storing calcium in bone

A

Formation

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9
Q

Of the total plasma calcium, ___ and ___ are regulated

A

free calcium; ionized calcium

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10
Q

______ calcium can be changed under acid-base disturbances

A

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

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11
Q

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

A

Ca binds to nerve axons

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12
Q

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

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

A

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

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13
Q

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

Are more/less calcium molecules bound to nerve axons?

A

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

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14
Q

Under what conditions does hypocalcemic tetany occur?

A
  • Hyperventilation (low plasma CO2) = respiratory Alkalosis
  • Decreased free calcium
  • Increased frequency of motor neuron AP (skeletal muscle contraction)
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15
Q

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

A

remodeling

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16
Q

What are the three stages of remodeling?

A

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

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17
Q

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

A

Amorphous crystals

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18
Q

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

A

B. Amorphous crystals

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19
Q

_____ 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

A

Hydroxyapatite crystals

slowly

20
Q

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

A

Hydroxyapatite crystals

21
Q

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

A

Osteocytes

22
Q
A
23
Q

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

A

1) M-CSF
2) OPG (osteoprotegerin)

24
Q

What two molecules bind to RANKL?

A

M-CSF and OPG

25
Q

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

A

C. Osteocyte

26
Q

___ secrete collagen and osteocalcin needed to form the osteoid

A

Osteoblast

27
Q

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

A

Binding of RANKL and M-CSF

28
Q

How do osteoclasts break down bone?

A

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

29
Q

What are the three roles of osteocytes?

A

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

30
Q

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

A

PTH = breakdown
Vit D = formation

31
Q

Which peptide is responsible for acute regulation of plasma ionized calcium?

Which molecule is responsible for long-term maintenance of strong bones?

A

PTH
Vit D

32
Q

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

A

Calcium sensing receptors (CaSR)

33
Q

Under what conditions is parathyroid hormone (PTH) secreted?

A

Low calcium

34
Q

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

A
35
Q

Why do individuals taking lithium often have greater bone breakdown?

A

Lithium stimulates PTH secretion and leads to a right shift of the curve

  • Secretion of PTH even under high calcium conditions
36
Q

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

1) Increase synthesis of ____
2) Decrease synthesis of ____

A

Increase synthesis of CaSR
Decrease synthesis of PTH

37
Q

What is the clinical indicator of Vit D?

A

25-OH-Vit-D3

38
Q

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?

A

Liver

Kidney

39
Q

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

A

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

40
Q

Where is pro-vit D made?
What is it converted to?

What stimulus is required for conversion?

A

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

41
Q

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

A

vitamin D3
(cholecalciferol)

thermal energy

42
Q

Vitamin D3 is hydroxylated in the liver to ____

A

25-OH-vitamin D3

43
Q

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

A

D. 25-OH-Vit D3 (calcidiol)

44
Q

Where is the Vit D receptor?

A

On the osteoblast

45
Q

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

A

1,25-(OH)2-
vitamin D

1α hydroxylase

46
Q

Where are Vit D receptors located?

A

Surface of osteoblast

47
Q

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

A

1) Osteoid formation
2) Calcium binding protein

Physiology II (23 decks)

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