Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BMS 460 FINAL > Lecture 33 > Flashcards

Lecture 33 Flashcards

1
Q

What function is calcium involved in?

A
  • Enzyme activation/inactivation
  • Intracellular second messenger
  • Exocytosis
  • Nerve conduction
  • Muscle contraction
  • Structural integrity of bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How much calcium is taken up by each system that stores/takes up calcium?

A
  • GI: +175mg/day (due to diet)
  • Kidneys: -175mg/day (lost in urine)
  • Bone: 0mg/day
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How much calcium does bone hold?

A

Holds about 99% or 1 kg of calcium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the chemical name for calcitrol?

A

1,25-(OH)2-D

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How does parathyroid hormone affect calcium?

A
  • Acts directly on bone and kidney to increase calcium
  • Through stimulation of calcitrol synthesis
  • Inhibits renal tubular reabsorption of phosphate which increases urinary phosphate secretion and decreases plasma levels.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where are parathyroid glands found?

A

On the posterior surface of the thyroid gland between capsule and surrounding connective tissue.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How many parathyroid glands are there?

A

4 major ones, may be a few accessory glands found in mediastinum or neck.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What do the 4 parathyroid glands derive from?

A

The third and fourth branchial pouches.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does the third branchial pouch differentiate into?

A
  • Inferior parathyroid glands
  • Thymus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does the fourth branchial pouch differentiate into?

A
  • Superior parathyroid glands
  • Ultimobranchial body
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two cell types within parathyroid glands?

A

Chief cells and oxyphil cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the function of a chief cell?

A

Synthesize and secrete PTH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the function of an oxyphil cell?

A

Unclear, appears to be a transitional form of chief cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the unique characteristics of oxyphil cells?

A
  • High amounts of mitochondria
  • Acidophilic staining in hematoxylin-eosin preparations
  • DOES NOT SECRETE PTH
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What signals chief cells to secrete PTH secretion?

A

A calcium sensing receptor (CaSR) senses a reduction in serum calcium levels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does increased parathyroid hormone affect serum calcium concentrations.

A

Serum calcium is increased.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is DiGeorge Syndrome (velo-cardio-facial syndrome)?

A

Absence of parathyroid glands and thymus which is caused by the deletion of a piece of chromosome 22 - “Catch-22”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does DiGeorge Syndrome present?

A

Features vary but is associated with hypocalcemia and may include birth defects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How is the immune system affected by velo-cardio-facial syndrome?

A

Infections are common in children due to an absent/hypoplastic thymus, which leads to problems with T-cell-mediated response

20
Q

What happens when calcium binds to CaSR?

A

The G-protein starts a signaling cascade that inhibits the PTH gene.

21
Q

How does calcitrol affect chief cells?

A
  • Directly inhibits PTH gene
  • Activates CaSR gene (follows central dogma, with preCaSR being the term for the pre-post translational modified protein)
22
Q

What happens when PTH gene is not inhibited?

A

PreproPTH is created from the gene, which then travels to the rough ER to be transformed into proPTH and then to PTH which is excreted via exocytosis.

23
Q

Other than repressing the gene, how does calcium sensing affect PTH secretion?

A

The downstream signaling pathway that is activated by the G protein inhibits the secretion of PTH.

24
Q

What is the signaling cascade that is caused by CaSR?

A

The G proteins inhibit adenylyl cyclase and stimulate phospholipase C (PLC) activity which results in suppression of PTH gene, accelration of intracellular degradation of PTH and inhibition of PTH release.

25
Q

How does the activation of PLC affect the intracellular workings of the chief cells?

A

Production of the second messengers inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG) from phosphoinostides (PIP2)

26
Q

How does second messengers in chief cells inhibit release of PTH?

A
  • IP3 increases levels of cytosolic calcium via the release of intracellular stores
  • DAG stimulates protein kinase C (PKC) activity
  • Elevated calcium and stimulated PKC inhibit release of granules containing PTH
27
Q

Why does high cytoplasmic calcium contrast in its mechanism vs. other secretory cells?

A

It inhibits the fusion of vesiles with the membrane of the parathyroid cell, which inhibits PTH.

28
Q

How do inactivating mutations of one allele of CaSR affect chief cells?

A
  • Prevents increased serum calcium, leading to increased PTH
  • Familial benign hypercalcemia (familial hypocalciuric hypercalcemia)
29
Q

What are the effects of familial benign hypercalcemia?

A
  • Severe if both alleles are inactivated
  • Skeletal changes of unremitting hyperparathyroidsim
  • Requires immediate parathyroidectomy in newborns
30
Q

How do activating mutations of CaSR affect chief cells?

A
  • Chief cells assume serum calcium is elevated when it is not, leading to decreased PTH
  • Hypocalcemia
31
Q

What are the effects of hypocalcemia?

A

Seizures can occur

32
Q

How to treat hypocalcemia?

A

Treat with supplemental PTH

33
Q

How can CaSR be affected by autoimmunity?

A
  • Inactivated - syndrome similar to familial benign hypercalcemia
  • Activated - hypoparathyroidism
34
Q

How does PTH affect bone?

A

Promotes calcium and phosphate resorption from bone by acting on stromal osteoblasts in the bone marrow to demineralize and release calcium

35
Q

How does PTH affect kidneys?

A
  • Promotes calcium reabsorption in proximal tubules of the renal cortex and in the distal nephron
  • Promotes phosphate excretion from the renal tubule.
  • Stimulates biosynthesis of active calcitrol which increases calcium absorption in the intestinal mucosa
36
Q

How does PTH affect the GI tract?

A

Promotes calcium absorption from the GI tract

37
Q

What reaction in the skin account for the first step of vitamin D activation?

A

7-dehydrocholesterol reacts with sunlight to form vitamin D3.

38
Q

What is plasma vitamin D made of?

A

Dietary vitamin D2/D3 and vitamin D3 from skin.

39
Q

What does the liver do with plasma vitamin D?

A

It combines with 25-hydroxylase to create 25-OH D.

40
Q

What do the kidneys do with 25-OH D?

A

It combines with 1-hydroxylase to create 1,25-(OH)2D (calcitrol)

41
Q

What are the three proteins that directly account for intestinal absorption of calcium?

A
  • Calcium-binding protein
  • Calcium-stimulated ATPase
  • Alkaline phosphatase
42
Q

25-Hydroxycholecalciferol has what effect secondary effect on the process of vitamin D activation?

A

Inhibits the further production of 25-hydroxycholecalciferol (25-OH D) in the liver to prevent excessive action of vitamin D3.

43
Q

Some calcium is secreted back into the small intestine

A

TRUE

44
Q

Where does calcitonin come from and where does it end up?

A

It comes from the kidney and ends up in the bones.

45
Q

What is released from bones to the extracellular fluid along with PTH?

A
  • Calctriol
  • Cortisol
46
Q

Components of total serum calcium under normal condition:

A
  • Albumin (4 Ca2+)
  • Phosphorus citrate (1 Ca2+)
  • Free Ca2+
  • Normal levels of PTH

BMS 460 FINAL (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions