Regulation of Calcium and Phosphate Metabolism Flashcards
1
Q
- _ contains most of the Ca2+ stores in the body
- _ is the biologically active form of Ca2+
- of the 60% . of unfilterable Ca2+, 10 % are _ and 50% are
A
- Bones/Teeth
- Free, ionized
- 10% is complexed to anions
- 50% are free ionized
2
Q
- What are symptoms of hypocalcemia?
A
- Hyperreflexia
- Spontaneous twitching
- Muscle cramps
- Numbness and tingling
- Tetany
3
Q
- What are two indicators of hypocalcemia?
A
- Chvostek sign: twitching of the facial muscles elicited by tapping on facial nerve
- Trousseau sign: Carpopedal spasm upon inflation of blood pressure cuff
4
Q
- What are symptoms of hypercalcemia?
A
- Decreased QT interval
- Constipation
- Lack of appetite
- Polyuria
- Polydipsia
- Muscle weakness
- Hyporeflexia
- Lethargy
- Coma
5
Q
- Hypocalcemia results in _ membrane excitability and is the basis for hypocalcemic tetany
- Hypercalcemia results in _ membrane excitability
A
- Hypocalcemia-increased membrane excitability (reduces activation threshold for Na+ channels, easier to evoke AP)
- Decreased (Nervous system becomes depressed and reflexes are slowed)
6
Q
Changes in calcium conentration can occur via what 3 primary ways?
A
- Changes in plasma protein concentration
- Increase in plasma protein, increase in total Ca2+ concentration and vice versa
- No change in Ca2+ ionized (protein changes are usually more chronic issues)
- Changing anion concentration
- Increase in Pi concentration will decrease Ca2+ ionized concentration
- Acid-Base Abnormalities
- Alters ionized concentration by changing the fraction of Ca2+ bound to Albumin
7
Q
- Changes in calcium levels during acidemia
- Changes in calcium levels during alkalemia
A
- Acidemia
- Increase in free ionized Ca2+ cuz less is bound to Albumin (H+ is taking Ca2+’s binding spots(
- Alkalemia
- Decrease in free ionized Ca2+ because more is bound to Albumin (often is accompanied by hypocalcemia)
8
Q
- What three organs are important in maintaining Ca2+ homeostasis?
- What three hormones are important in maintainin Ca2+ homeostasis?
A
- Bone, kidney, intestine
- PTH, Vitamin D, Calcitonin
9
Q
- Identify the following hormones in their role in Ca2+ homeostasis
A
- Vitamin D
- PTH
- Vitamin D
- Calcitonin
- PTH (promotes reabsorption of Ca2+ and excretion of PO43-)
10
Q
- What is the relationship between Ca2+ and PO43- concentration in the ECF?
- Most Pi is distributed in _
- The 1% that is in the plasma, some is _, some _ bound and some _
A
- Inversely proportional to one another (high ca2+, low Pi)
- Both are regulated by the same hormones
- Most is distributed in bone (85%)
- Ionized (84%), Protein bound, Complexed to cations
11
Q
- PTH is secreted by _ cells in the _ gland
- _ is the stimuli for secretion
- Synthesis of PTH
- Synthesized as a _
- Eleaved to form _
- Transported to golgi and cleaved to form _
- 84 aa’s long with most biologically active portion of the hormone being located towards the _ terminus of the AA
A
- Chief cells, Parathyroid
- Decreased serum Ca2+
- preprohormone
- prohormone
- PTH
- N terminus (AAs 1-34)
12
Q
-
Regulation of PTH gene expression and secretion
- Increased Ca2+ levels in the blood are sensed by the _ receptor and activate _ and _ downstream signaling pathways to inhibit PTH gene transcription and exocytosis of PTH
- _ inhibits PTH gene transcription and promotes transcription of _ gene
A
- CaSR
- Gq and Gi (note Gq is inhibitory in this case)
- 1,25 Vitamin D-promotes CaSR gene transcription
13
Q
-
Chronic hypercalcemia
- _ PTH synthesis and storage, and _ breakdown of stored _ and release of inactive fragments into the bloodstream
-
Chronic hypocalcemia
- _ PTH synthesis and sotrage
- _ of parathyroid glands (2ndary _)
-
Magnesium
- Parallels PTH secretion
-
Severe Hypomagnesemia (EX: Alcoholism)
- _ of PTH storage, synthesis and secretion
A
- Decrease, increase breakdown of stored PTH
- Increase PTH synthesis and storage
- Hyperplasia (2ndary hypoparathyroidism)
- Decrease
14
Q
- PTH acts on the bone and kidney tubule via which type of receptor?
A
- GPCR (Gs)
- Increased cAMP and adenylyl cyclase and PKA
15
Q
- Action of PTH in the bone
- Action of PTH on the kidney
- Action of PTH on the intestine
A
- Increase bone resorption
- Increased reabsorption of Ca2+, Increased excretion of Pi and cAMP in the urine
- Indirectly increases absorption of Ca2+ from intestine d/t actions of Vitamin D
16
Q
Function of Vitamin D
Properties of its synthesis
Has a _ receptor with what two receptor components
A
- Functions
- Increase Ca2+ and Pi plasma concentrations
- Increase Ca2+ and Pi product to promote mineralization of new bone
- Has actions on intestine, kidney, and bone
- Synthesis
- Made as a prohormone
- Hydroxylated at least twice to form an active metabolite
- Regulated by (-) feedback
- Has nuclear receptor (with Vitamin D receptor component and Retinoid X component)