Hormonal Control of Ca2+ Homeostasis Flashcards
What is the importance of Ca2+ in the body?
- Structural component of bones and teeth
- Blood clotting
- Maintains transmembrane potential of cells
- Muscle contraction
- Second messenger in hormonal and neurocrine signal transduction
Ca2+ plays a vital role in various physiological processes, highlighting its significance in maintaining overall health.
Where is the majority of body calcium found?
In bone, approximately 99% of calcium is tied up in the mineral phase
The remaining 1% exists in a pool that can rapidly exchange with extracellular calcium.
What are the three major target organs for calcium regulation?
- Bone
- Intestine
- Kidney
These organs play critical roles in maintaining calcium homeostasis through various processes.
What is the process of breaking down and assimilating calcium called?
Resorption
This process involves the mobilization of Ca2+ from bone into the bloodstream.
What hormone increases circulating [Ca2+]?
Parathyroid hormone (PTH)
PTH is a key regulator of calcium levels in the blood.
What hormone decreases circulating [Ca2+]?
Calcitonin (CT)
Calcitonin functions to lower blood calcium levels by inhibiting osteoclast activity.
What is the primary function of parathyroid hormone (PTH)?
To raise [Ca2+] in blood
PTH acts on bones, kidneys, and indirectly on the intestine to increase calcium levels.
What hormone acts to facilitate absorption of Ca2+ from the small intestine?
Vitamin D (1,25-DHC)
Vitamin D is essential for calcium absorption and is activated by PTH in the kidneys.
What condition is characterized by low blood calcium concentration?
Hypocalcemia
Hypocalcemia can lead to various health issues, including muscle spasms and bone problems.
What is primary hyperparathyroidism most commonly due to?
A parathyroid tumor (adenoma)
This condition leads to uncontrolled secretion of PTH and elevated blood calcium levels.
What triggers the release of calcitonin?
Elevated blood Ca2+ levels
Calcitonin is released to counteract high calcium levels by promoting calcium deposition in bones.
What is milk fever caused by?
A severe drop in blood calcium concentration
This condition is common in postpartum cows due to high calcium demands for milk production.
Fill in the blank: The main function of calcitonin is to _______ bone resorption.
inhibit
By inhibiting osteoclasts, calcitonin helps to decrease blood calcium levels.
What is secondary hyperparathyroidism often caused by?
- Kidney disease
- Inadequate nutrition (e.g., low calcium or vitamin D)
These conditions lead to excessive secretion of PTH to compensate for low blood calcium levels.
True or False: PTH and Vitamin D work together to enhance calcium absorption.
True
Both hormones facilitate calcium absorption from the intestine and mobilization from bone.
What happens to calcium levels during parturition in cows?
Calcium concentrations abruptly drop
This drop triggers an increase in PTH concentrations to maintain calcium levels.
What condition is indicated by concentrations within the red area?
Clinical hypocalcemia
Adapted from Hernández-Castellano et al. (2017)
What is the DCAD method used for?
Preventing Milk Fever
DCAD stands for Dietary Cation-Anion Difference
What dietary change can help prevent Milk Fever?
Feeding a calcium-deficient diet
This can stimulate PTH secretion
How does higher dietary magnesium affect blood pH?
It helps reduce blood pH
Magnesium is crucial for metabolic processes
What happens if total absorbed dietary calcium is substantially less than required?
Stimulates secretion of PTH
This aids in bone Ca resorption and intestinal Ca absorption
What are anionic salts?
Minerals with a high proportion of anions
Anions are negatively charged
What is the effect of lowering dietary cations and increasing dietary anions before parturition?
Lowers the pH of blood
This enhances tissue responsiveness to PTH
What is the role of anionic salts in the diet?
Reduces Dietary Cation-Anion Difference
This action helps in Milk Fever prevention
What is the common method for treating Milk Fever?
IV injection of calcium salts
Usually calcium borogluconate
What should be administered slowly to avoid cardiac arrest?
Blood calcium levels
Rapid administration can be dangerous
What supplements can be given around parturition?
Calcium and phosphorus supplements (oral gels)
These help maintain calcium levels
Fill in the blank: Anions are ______ charged.
negatively
Cations are positively charged
True or False: The DCAD method involves increasing dietary cations.
False
It involves decreasing dietary cations and increasing anions
