Brainscape's Knowledge GenomeTM

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


See full index

Metabolism > Session 11 - incomplete > Flashcards

Session 11 - incomplete Flashcards

0
Q

In what form, where and within what ranges is calcium carefully regulated?

A
  • Plasma concentration of free ionised calcium (Ca2+)

- 1.0 - 1.3 mmol/L

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

In what cellular processes does calcium play a critical role?

A
  • Hormone secretion
  • Muscle contraction
  • Nerve conduction
  • Exocytosis
  • Activation/inactivation of many enzymes
  • Intracellular second messenger (carries information from cell membrane to cell interior)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where is most calcium in the body located?

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

What is the physiologically active form of calcium?

A
  • Ca2+ (free ionised calcium in plasma)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In what form does calcium exist in the plasma?

A
  • Free ionised species (Ca2+) (45%)
  • Bound to/associated with a anionic sites on serum proteins, especially albumin (45%)
  • Complexed with low-molecular-weight organic anions (eg citrate and oxaloate (10%)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the total normal concentration of all forms of calcium in the plasma?

A
  • 2.2-2.7 mmol/L
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the importance of phosphate?

A
  • Part of the adenosine triphosphate molecule

- Therefore plays a crucial role in: cellular energy metabolism; activation/inactivation of enzymes

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

Is phosphate strictly regulated?

A
  • No

- Fluctuates during the day eg after meals

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

How are calcium and phosphate linked?

A
  • Are both the major components of hydroxyapatite crystals [Ca10(PO4)6(OH)2], which constitute the major portion of the mineral in bone
  • Regulated by the same hormones: parathyroid hormone (PTH); 1,25-dihydroxyvitamin D (calcitriol) and to a lesser extent calcitonin. Hormones act on the bone, kidneys and the gastrointestinal tract to control levels of these two ions in the plasma. Actions of these hormones on calcium and phosphate are opposed ie a particular hormone may raise levels of one ion while lowering the other
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the key hormones involved in the control of calcium levels in serum?

A
  • Parathyroid hormone (PTH)

- Vitamin D (active form calcitriol)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What effect do certain hormones have on serum calcium levels?

A
  • Parathyroid hormone and vitamin D (calcitriol): raise serum calcium concentrations
  • Calcitonin: lowers serum calcium in animals during pregnancy to protect maternal skeleton (lower serum calcium -> lower osteoclast activity); released from thyroid gland (if thyroid gland is removed there is no effect of calcium homeostasis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is serum calcium regulated by hormones?

A
  • Changes in Ca2+ concentration alters PTH by negative feedback
  • Detected by unique G-protein receptors in chief cell surface
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens when [Ca2+] is high?

A
  • Increased Ca2+ -> binds to G-protein receptor -> stimulates Phospholipase C (PLC) -> inhibits adenylate cyclase -> reduced cAMP -> reduced PTH release
  • Reverse happens when Ca2+ is low
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which hormone controls the short term regulation of serum calcium?

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

What hormone controls the long term regulation of serum calcium?

A
  • Calcitriol (active form of Vitamin D)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is vitamin D and what types are there?

A
  • Group of biologically inert prohormones that must undergo 2 hydroxylation reactions to be activated
  • Vitamin D2 (ergocalciferol) and D3 (cholecalciferol)
16
Q

Where does Vitamin D come from?

A
  • Formed in the skin

- Absorbed in the gut from the diet

17
Q

What happens to vitamin D in the body and why?

A
  • Converted to calciferol (25-hydroxyvitamin D) in the liver
  • Vitamin D has a shorter half life than calciferol (~2 weeks)
  • Is then converted to its final from calcitriol in the kidney
18
Q

Is vitamin D regulated?

A
  • No

- But final conversion to calcitriol in the kidneys is regulated by PTH (hormones are linked)

19
Q

How is Vitamin D2 produced and what is its action?

A
  • Absorbed by gut

- No action (is a prohormone)

20
Q

Where is Vitamin D3 produced and what is its action?

A
  • Skin in the presence of UV light

- No action (is a prohormone)

21
Q

Where is Calciferol produced and what is its action?

A
  • Liver (1st hydroxylation of Vitamin D)

- No action (prohormone)

22
Q

Where is Calcitriol produced and what is its action?

A
  • Kidney (2nd hydroxylation of Vitamin D)

- ⬆️ Ca2+ absorption (binds to Ca2+ in the gut)

23
Q

Where is parathyroid hormone produced and what is its function?

A
  • Parathyroid gland
  • ⬆️ conversation of calciferol -> calcitriol
  • ⬆️ Ca2+ release from bone
  • ⬆️ Ca2+ reabsorption in kidney
24
Q

What does PTH a do in the kidney?

A
  • Affects tubular cells in kidney causing increased Ca2+ reabsorption in the distal convoluted tubule (DST)
  • Pi is removed from the circulation by the inhibition of reabsorption of the promimal convoluted tubule, which prevents calcium stones forming
25
Q

What causes hypocalcaemia and what does it cause?

A
  • Causes hyper-excitability in the nervous system, including the neuromuscular junction leading to paraesthesia (tingling sensation), then tetany (involuntary muscle contraction), paralysis and even convulsions
  • Caused by low amount of Ca2+ bound to neuromuscular junctions, allowing Na+ to depolarise it much more readily
26
Q

What does hypercalcaemia cause?

A
  • Formation of kidney stones (renal calculi)
  • Constipation
  • Dehydration
  • Kidney damage
  • Tiredness
  • Depression
    (Moans, Stones, Groans)
27
Q

What is the treatment for hypercalcaemia?

A
  • Fluids to treat dehydration from excess fluid loss in urine
  • Removal of benign tumour in one of the parathyroid glands (as hyperparathyroidism -> hypercalcaemia)
28
Q

When is parathyroid hormone related peptide produced (PTHrP)?

A
  • Peptide hormone produced in tumours which may lead to hypercalcaemia
  • PTHrP is secreted by some cancer cells leading to humoral hypercalcaemia of malignancy (HHM)
  • Commonly seen in patients with breast/prostate cancer and occasionally with myeloma
29
Q

What can the measurement of parathyroid hormone related peptide help?

A
  • Determining the cause of otherwise unexplained hypercalcaemia
30
Q

What does PTHrP do in the body?

A
  • Is similar to PTH
  • ⬆️ calcium release from bone
  • ⬇️ renal calcium excretion
  • ⬇️ renal phosphate reabsorption
  • Does not increase C-1 Hydroxylase activity and therefore doesn’t increase calcitriol concentration

Metabolism (11 decks)

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