Changes

*Milk Production  

*Milk Production  

*Bone Functioning  

*Bone Functioning  

||[[Endocrine System - Calcium Homeostasis - Anatomy & Physiology|Answer article]]

||[[Calcium Homeostasis - Anatomy & Physiology|Answer article]]

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|<big>Which Three hormones affect calcium homeostasis, and what organs synthesize them?

|<big>Which Three hormones affect calcium homeostasis, and what organs synthesize them?

*Calcitriol aka Active Vitamin D3 - activated in the kidney

*Calcitriol aka Active Vitamin D3 - activated in the kidney

*Calcitonin - from the C Cells of the thyroid gland.

*Calcitonin - from the C Cells of the thyroid gland.

||[[Endocrine System - Calcium Homeostasis - Anatomy & Physiology#Calcium Metabolism|Answer article]]

||[[Calcium Homeostasis - Anatomy & Physiology#Calcium Metabolism|Answer article]]

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|<big>Give the 4 Actions of PTH.

|<big>Give the 4 Actions of PTH.

*Increases calcium absorption from the gut indirectly, by activating Vitamin D3.

*Increases calcium absorption from the gut indirectly, by activating Vitamin D3.

*Decreases calcium and magnesium excretion in the kidneys at the expense of phosphorus

*Decreases calcium and magnesium excretion in the kidneys at the expense of phosphorus

||[[Endocrine System - Calcium Homeostasis - Anatomy & Physiology#PTH Actions|Answer article]]

||[[Calcium Homeostasis - Anatomy & Physiology#PTH Actions|Answer article]]

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|<big>What are the sources of Vitamin D?

|<big>What are the sources of Vitamin D?

* Dietary - Vitamin D3 is from animal food sources, Vitamin D2 is from plant food sources.

* Dietary - Vitamin D3 is from animal food sources, Vitamin D2 is from plant food sources.

*Skin - 7-dehydrocholesterol is converted to vitamin D3 by Ultraviolet radiation at wavelength 300nm in the skin.

*Skin - 7-dehydrocholesterol is converted to vitamin D3 by Ultraviolet radiation at wavelength 300nm in the skin.

||[[Endocrine System - Calcium Homeostasis - Anatomy & Physiology#Calcitriol|Answer article]]

||[[Calcium Homeostasis - Anatomy & Physiology#Calcitriol|Answer article]]

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|<big>Describe the synthesis of Active Vitamin D3 (Calcitriol)

|<big>Describe the synthesis of Active Vitamin D3 (Calcitriol)

*In the liver it's converted to '''25-hydroxycholecalciferol''' - 25(OH)Vitamin D3.  

*In the liver it's converted to '''25-hydroxycholecalciferol''' - 25(OH)Vitamin D3.  

*Within the kidney, 25-hydroxycholecalciferol is further 'hydroxylated' using the enzyme '1-a-Hydroxylase'. to create '''1,25-dihydroxycholecalciferol''' = ACTIVE VITAMIN D3.

*Within the kidney, 25-hydroxycholecalciferol is further 'hydroxylated' using the enzyme '1-a-Hydroxylase'. to create '''1,25-dihydroxycholecalciferol''' = ACTIVE VITAMIN D3.

||[[Endocrine System - Calcium Homeostasis - Anatomy & Physiology#Calcitriol|Answer Article]]

||[[Calcium Homeostasis - Anatomy & Physiology#Calcitriol|Answer Article]]

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|<big>What are the actions of Calcitriol?

|<big>What are the actions of Calcitriol?

*'''Decreases Calcium and Phosphorous excretion via the kidney''' - Calcitriol acts on the renal tubular epithelial cells to increase calcium and phosphorous reabsorption from the nephron. This action is WEAK compared to the PTH action (which acts to reabsorb calcium but lose phosphorous from the nephron).

*'''Decreases Calcium and Phosphorous excretion via the kidney''' - Calcitriol acts on the renal tubular epithelial cells to increase calcium and phosphorous reabsorption from the nephron. This action is WEAK compared to the PTH action (which acts to reabsorb calcium but lose phosphorous from the nephron).

*'''Normal bone functioning (osteoclast and osteoblast functions)''' - Calcitriol is needed for normal bone absorption and deposition. Without Vitamin D3, bone is not resorbed in response to PTH.

*'''Normal bone functioning (osteoclast and osteoblast functions)''' - Calcitriol is needed for normal bone absorption and deposition. Without Vitamin D3, bone is not resorbed in response to PTH.

||[[Endocrine System - Calcium Homeostasis - Anatomy & Physiology#Calcitriol|Answer Article]]

||[[Calcium Homeostasis - Anatomy & Physiology#Calcitriol|Answer Article]]

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|<big>What is the function of Calcitonin and how does it work?

|<big>What is the function of Calcitonin and how does it work?

**Slow Phase - puts calcium into bone by reducing formation of new osteoclasts.

**Slow Phase - puts calcium into bone by reducing formation of new osteoclasts.

There are also slight (insignificant) effects on the kidney and GIT.

There are also slight (insignificant) effects on the kidney and GIT.

||[[Endocrine System - Calcium Homeostasis - Anatomy & Physiology#Calcitonin|Answer Article]]

||[[Calcium Homeostasis - Anatomy & Physiology#Calcitonin|Answer Article]]

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|<big>How does the body raise blood calcium levels:

|<big>How does the body raise blood calcium levels:

*By increasing PTH concentration  

*By increasing PTH concentration  

*By increasing Active Vitamin D3

*By increasing Active Vitamin D3

||[[Endocrine System - Calcium Homeostasis - Anatomy & Physiology#Summary|Answer article]]

||[[Calcium Homeostasis - Anatomy & Physiology#Summary|Answer article]]

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|<big>How does the body lower blood calcium levels:

|<big>How does the body lower blood calcium levels:

*By reducing Vitamin D activation  

*By reducing Vitamin D activation  

*By increasing Calcitonin synthesis and secretion.

*By increasing Calcitonin synthesis and secretion.

||[[Endocrine System - Calcium Homeostasis - Anatomy & Physiology#Summary|Answer article]]

||[[Calcium Homeostasis - Anatomy & Physiology#Summary|Answer article]]

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