Brainscape's Knowledge GenomeTM

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


See full index

Endocrine Physiology > Calcium Haemostasis > Flashcards

Calcium Haemostasis Flashcards

1
Q

Roles of calcium

A 
Signalling
Blood clotting
Apoptosis
Skeletal strength 
Membrane excitability
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does Ca2+ decrease the permeability of?

A

Na+

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

Hypocalcaemia effect on membrane excitability

A

Increases neuronal Na+ permeability leading to hyperexcitation of neurones

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

In extreme cases what can hypocalcaemia lead to (in respect to membrane excitability)?

A

Tetany - if spreads to larynx and resp muscles - asphyxiation

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

Hypercalcaemia effect on membrane

A

Decreases neuronal Na+ permeability which will reduce excitability and depress neuromuscular activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What can hypercalcaemia trigger in extreme cases?

A

Cardiac arrhythmias

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

Distribution of calcium in the body

A

99% bones (1g)

  1. 9% intracellular fluid
  2. 1% extracellular fluid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where is the calcium found in intracellular fluid?

A

Mostly stored in the mitochondria and sarcoplasmic reticulum.
Free [Ca2+]ic very low

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

Where is calcium found in the extracellular fluid?

A

Nearly half ECF Ca2+ is bound to protein

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

How much of calcium in the body is free in solution and physiologically active?

A

0.05%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is most of the calcium stored in bone stored in the form of? And what does this mean is also important in determining calcium balance?

A

Hydroxyapatite

Phosphate homeostasis is also important

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

Level of calcium in the plasma

A

2.2 - 2.6mM (0.1%)

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

What does calcium have a high affinity for?

A

Proteins

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

How much of calcium is bound to plasma proteins in the plasma?

A

40%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Remaining 10% of plasma calcium ions that are neither bound to plasma proteins nor free are bound to what?

A

Plasma anions

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

How much of the calcium in the plasma is freely ionised and therefore physiologically active?

A

50%

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

What is the amount of calcium that is bound to protein dependent on?

A

pH of the ECF

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

What conditions does binding capacity of Ca2+ increase under?

A

Alkalotic conditions

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

What happens to calcium binding in acidosis?

A

Binding capacity reduces

Free [Ca2+] rises

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Total body calcium = ?

A

Ca2+ from diet - Ca2+ excretion at kidney and faeces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Main function of bone

A

Role in maintaining Ca2+ balance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does the bone do when calcium levels are low? What does this lead to?

A

Release calcium at the expense of bone strength

Leads to brittle and weak bones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Function of osteoblasts

A

BONE BUILDING CELLS

Lay down a collagen extracellular matrix which they then calcify

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Function of osteocytes

A

Regulate the activity of osteoblasts and osteoclasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What do osteoblasts differentiate to form?

A

Osteocytes

26
Q

Function of osteoclasts

A

Secrete H+ ions to dissolve the calcium salts and also provide proteolytic enzymes to digest the extracellular matrix

27
Q

What are the two key hormones that act to increase [Ca2+]plasma?

A 
Parathyroid hormone (PTH)
Calcitriol
28
Q

What is parathyroid hormone produced by?

A

Parathyroid glands

29
Q

What is calcitriol and active form on?

A

Vit D3

30
Q

What type of hormone is parathyroid hormone (PTH)?

A

Polypeptide hormone

31
Q

What type of hormone is calcitriol?

A

Steroid hormone

32
Q

What is calcitriol produced from and by?

A

From vitamin D

Liver and kidneys

33
Q

How many parathyroid glands are there?

A

4

34
Q

Where do the parathyroid glands lie?

A

On the posterior surface of the thyroid gland

35
Q

What is parathyroid hormone (PTH) released in response to?

A

A decrease in free [Ca2+] in the plasma

36
Q

What is done to increase free [Ca2+] by PTH?

A

Stimulates osteoclasts to release Ca2+ and phosphate from bone
Inhibiting osteoblasts to reduce Ca2+ deposition in bone
Increasing reabsorption of Ca2+ from the kidney tubules, therefore decreasing its excretion in the urine
Increases renal excretion of phosphate.
Stimulates the kidney to synthesise calcitriol from vitamin D

37
Q

How long does it take for the effects to be seen from PTH stimulating osteoclasts to release Ca2+ and phosphate into bone?

A

12 - 24 hours

38
Q

How does increasing the renal excretion of phosphate lead to an increased free [Ca2+] in the plasma?

A

It prevents Ca2+ from being deposited back into the bone, a process requiring phosphate

39
Q

Where does calcitriol promote calcium absorption?

A

Gut

Kidney

40
Q

What does calcitriol complement the action of and what does this do?

A

PTH

Increases [Ca2+] plasma

41
Q

Sources of Vitamin D3

A

Cholesterol derivatives from UV sunlight on the skin
Fatty fish e.g. tuna
Fish liver oils
Egg yolks

42
Q

Formation of calcitriol from Vit D3 is stimulated by what?

A

Prolactin in lactating woman

43
Q

Functions of calcitriol

A

Increase absorption of Ca2+ from the gut
Facilitates renal absorption of Ca2+
Mobilises calcium stores in bone by stimulating osteoclast activity

44
Q

What controls the active transport system which moves Ca2+ from the intestinal lumen to the blood?

A

Calcitriol

45
Q

What does prolactin stimulate the synthesis of? Why?

A

Calcitriol

Increased demand for Ca2+ for milk production in lactation

46
Q

The circulating level of what controls the proportion of dietary calcium absorbed from the intestine?

A

Calcitriol

47
Q

What is the level of vitamin D to be classified as Vitamin D deficiency?

A

< 20ng/ml

48
Q

Over what age is vitamin D deficiency more common in and why?

A

> 65 y/o

Reduced gut absorption, reduced Ca2+ mobility

49
Q

Pathology of Vit D deficiency leading to weak bones (rickets/osteomalacia)?

A 
Vit D deficiency 
Intestinal malabsorption of Ca2+
Decreases [Ca2+] plasma
Which promotes PTH 
Which promotes phosphate deficiency 
Aggravates Ca2+ loss from bone
50
Q

What two populations are most at risk of Vit D deficiency?

A

Elderly

Asian

51
Q

Pigmented skin and vit D relationship

A

Pigmented skin less able to make vit D3 in response to UV light

52
Q

What is vit D deficiency implicated in?

A

MS
Cancer
Arthritis
CVD

53
Q

What is the key hormone which acts to decrease [Ca2+] plasma?

A

Calcitonin

54
Q

What type of hormone is calcitonin?

A

Peptide hormone

55
Q

Where is calcitonin produced from?

A

Thyroid gland

56
Q

What is the secretion of calcitonin stimulated by?

A

Increased [Ca2+] plasma

57
Q

What is any excess of calcitonin overridden by and what does this mean?

A

PTH

Not important to humans really

58
Q

Cortisol effects on bone formation

A

Inhibits osteoblasts, increases renal excretion of Ca2+ and phosphate and reduces intestinal absorption of Ca2+
This over time can produce osteoporosis

59
Q

Insulin effect on bone formation

A

Increases bone formation

Antagonises effects of cortisol

60
Q

Oestrogen effect on bone formation

A

Promotes bone formation via oestrogen receptors on osteoblasts

61
Q

GH on bone formation

A

Constant stimulus for bone formation

62
Q

Prolactin effect on bone formation

A

Promotes calcium absorption from the gut by stimulating synthesis of calcitriol

Endocrine Physiology (8 decks)

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