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Medicine Sem 1 > Physiology week 13 > Flashcards

Physiology week 13 Flashcards

1
Q

What is calcium important for

A
  • muscle contraction, nere impulse transmission and blood clottin
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2
Q

What are the effects of abnormal levels of calcium

A

Hypercalcemia: Depresses the nervous system.
Hypocalcemia: Increases nervous system excitability.

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3
Q

Explain the distibution of calcium

A
  • ECF - 0.1%
    -Cells and organelles 1%
    -Stored in bones 99%
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4
Q

Explain phosphate distribution

A
  • Bones - 85%
    -Cells- 14-15%
    -ECF - less than 1 %
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5
Q

Name the three forms in which calcium exists as in the plasma
- Whether they are diffusible or nont

A

-Bound to plasma proteins , non-diffusible
-Bound to anionic substances , diffusible
-Ionized calcium , diffusible

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6
Q

Name the 2 forms in whcih inoranic phosphate exists as in the plasma

A
  • HP04 2-
    -H2P04 2-
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7
Q

and alkaline pH Explain the effect of an acidic pH on the 2 forms of inorganic phosphate

A

Acidic pH: Increases H₂PO₄⁻, decreases HPO₄²⁻.
Alkaline pH: Opposite effect.

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8
Q

Large changes in extracellular phopshate levels lead to..

A
  • Minimal psyhcological effects
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9
Q

Changes in calcium levels cause..

A
  • Significant immediate effects
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10
Q

What is the effect of Hypocalcemia

A
  • Tetany
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11
Q

What is calcium absorption facilitated by

A
  • Vitamn D
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12
Q

How is phosphate absorbed

A
  • Absorbed into the blood from the gut
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13
Q

What happens to phosphate during excretion

A
  • Phospate is combined with non absorbed calcium in the feces
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14
Q

Name the 2 types of bone

A

-Cortical(compact) bone
-Trabecular(spongy) bone

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15
Q
A
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16
Q

What is the structure of cotical (compact) bone
Where is it found

A
  • Has a dense outer layer forming 80% of bone mass
  • SHafts of long bones
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16
Q

What is the function of the cortical(compact bone)

A

supports body weight

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17
Q

Where is the Trabecular bone found

A
  • At the ends of long bones,joints and vertebrae
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17
Q

What is the structure of the Trabecular(Spongy)bone +
What does it contain

A
  • Has a porous inner bone, forming 20% of bone mass
    -Red bone marrow for RBC production
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18
Q

What is the bone composed of

A
  • Organic Matrix
19
Q

What is the organic matrix in the bone composed of and functions

A
  • 90-95% of collagen fibers, providing tensile strength
  • The remainder is groundsubstances ( proteoglycans like chondroitin sulfate ) that aid calcium salt deposition and bone repair
20
Q

Name the 2 types of bone strength

A
  • Tensile strength
    -Compressional strength
21
Q

What provides tensile strength

A
  • Collagen fibers alligned along tension lines
22
Q

What provides compressional strength

A
  • Calcium salts
23
Q

What causes precipitation of hydroxyapatite

A
  • High enough calcium and phosphate concentrations
24
Q

What prevents precipitation in tissues other than the bone

A
  • Inibitiors such as : Pyrophosphate
25
Q

Explain the initial stage of bone calcification

A

-Osteoblasts secrete collagen monomers and ground substance (proteoglycans).
-Collagen fibers form, creating osteoid
-Some osteoblasts become trapped in osteoid, becoming osteocytes.

26
Q

What happens after the initial stage of bone calcification

A
  • Calcium starts precipitates
27
Q

Explain the calcium salt precipation step in bone calcifictaion

A

Begins on collagen fibers, forming minute nuclei that grow into hydroxyapatite crystals over time.
Initial salts deposited are amorphous (noncrystalline) compounds.
Amorphous salts can quickly supply calcium when needed.

28
Q

What is the role of pyrophosphate in bone precipitation

A
  • Inhibits hydroxyapatite crystalization
29
Q

What is pyrophosphate regulated by

A

-TNAP
-NPP1
-ANK

30
Q

What is the function of TNAP as a regulator of pyrophosphate

A
  • Breaks down pyrophosphate allowing calcification
31
Q

What is the function of NPP1 as a regulator of pyrophosphate

A
  • Produces extracellular pyrophosphate
32
Q

What is the function of ANK as a regulator of pyrophosphate

A
  • Transports pyrophosphate fromm the cell interior to the surface
33
Q

What is the effect of low TNAP in relation to calcification

A

Results in poor bone mineralization

34
Q

What is the effect of low NPP1 and ANK on calcification

A
  • Leads to excessive calcification
35
Q

What is the role of Exchangeable calcium in bone

A

Maintains equillibrium with extracellular calcium ions

36
Q

Where is exchangeable calcium present

A
  • Tissue cells like the ones in the liver and gastrintestinal tract
37
Q

Where are osteoblasts found

A

on bone surfaces and trabecular cavities

38
Q

What is the function of osteoblast cells

A
  • Bone depostition
39
Q

What is the function of osteoclasts

A
  • Bone resorption
40
Q

Explain the mechanism of Bone resorption by osteoclasts

A
  • Form a ruffedl border to secrete:
    -Proteolytic enzymes
    -Acids
  • Then the bone particles are phagocytosed,dissolved and released into the blood
41
Q

What is the function of PTH in relation to bone resporption and deposition

A
  • PTH indirectly stimualtes osteoclasts activity by acting on osteoblasts
42
Q

What is the function of Osteoprotegrin(OPG) in relation to bone resorption
+ what produces it

A
  • Inhibits bone resorption by binding to to RANKL preventing osteoclast maturation
  • Produced y Osteoblasts
43
Q

What is the function of RANKL and what is it secretd by

A

Binds to RANK receptors on osteoclacts promoting osteoclasts maturation

44
Q

Name 4 hormones that have influences on bone remodelling

A

-PTH and vitamin D
-Glucocorticoids
-Estrogen

45
Q

What is the funcion of the hormones PTH and vitamin D togther

A
  • Stimulates RANKL production and inhibits (osteoptoegrin ) OPG
46
Q

What is the function of Glucoorticoids

A

-Increases RANKL and decreases OPG increasing bone resorption

47
Q

What is the function of Estrogen

A

-Increases OPG reducing bone , decreasing bone resorption

Medicine Sem 1 (33 decks)

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