L10 Flashcards
(145 cards)
1
Q
What role does calcium play in intracellular signaling?
A
Acts as a messenger
2
Q
How is calcium involved in hormone secretion?
A
Key for insulin release
3
Q
What function does calcium have in blood clotting?
A
It’s a cofactor
4
Q
How does calcium affect neural excitability?
A
Relies on calcium
5
Q
What role does calcium play in muscle contraction?
A
Relies on calcium
6
Q
What is calcium’s role in bone?
A
Building and maintaining
7
Q
What is the effect of calcium on plasma membranes and cells?
A
Affect the resting membrane potentials
8
Q
Where is calcium located in the body?
A
- Extracellular matrix
- Extracellular fluid
- Intracellular
9
Q
Where is most of the calcium trapped?
A
Bones
10
Q
What percentage of calcium is in the ECF?
A
0.1%
11
Q
Where is calcium absorbed?
A
Small intestine
12
Q
How is excess calcium outputted?
A
Urine
13
Q
What percentage of calcium is in the cells?
A
0.9%
14
Q
What is the ability of calcium?
A
To move between bone to the ECF and then from the ECF to in and out of cells as well
15
Q
What happens to dietary calcium intake?
A
It goes in through our small intestine, eventually to the ECF and then carried through to bone
16
Q
What happens to too much calcium?
A
It gets filtered through the kidneys and goes out into our urine
17
Q
What percentage of calcium is fine tuned with hormones?
A
1%
18
Q
What is the importance of the small intestine?
A
Where the calcium is absorbed
19
Q
What is the main form of calcium in bone?
A
Hydroxyapatite
- Trapped through crystals
20
Q
Is bone static or dynamic?
A
Dynamic
21
Q
What two components are in hydroxyapatite?
A
Calcium and phosphate
22
Q
What does bone contain?
A
Blood vessels and nerves
23
Q
What is a small fraction of calcium in bone?
A
Ionized and readily exchangeable
24
Q
What is bone constantly doing?
A
Being formed and resorbed
25
What is the main component of bone?
Calcium
26
What is the function of osteoblasts?
Bone forming cells
27
What do osteoclasts do?
Break down bone
28
What is the role of osteocytes?
Maintain bone
29
What are osteocytes previously?
Osteoblasts
30
What do osteocytes maintain?
Bone in its immediate vicinity
31
What is making bone?
Creating calcium phosphate complexes
32
What happens to osteoblasts when trapped by bone matrix?
Become osteocytes
33
Which cells lay down matrix?
Osteoblasts
34
Which cells are responsible for bone resorption?
Osteoclasts
35
What is the calcium turnover rate in infants?
100% per year
36
What is the calcium turnover rate in adults?
18% per year
37
What is the ruffled border?
A structure that eats away at bone
38
How do osteoclasts attach to the bone matrix?
Like a suction cup
39
What do osteoclasts secrete?
HCl
40
What is the role of proteases?
Break down bone
41
What happens to calcium during bone resorption?
It becomes ionized
42
What is the function of Carbonic Anhydrase (CA)?
Produces bicarbonate and protons
43
Where does the ionized calcium go?
Into the bloodstream
44
What is the purpose of secreting HCl?
To eat away at the bone
45
What is the bone remodeling cycle?
Osteoclasts resorb, osteoblasts form
46
What is bone remodeling for?
Microfracture repair
47
How long does the bone dynamics cycle take?
Around 100 days
48
What is the ultimate goal of bone remodeling?
Repair old bone and replace with new tissue
49
What is RANK?
Receptor activator of nuclear factor kappa B
50
What is RANKL?
RANK ligand
51
What does OPG do?
Blocks RANKL/RANK interaction
52
What is the role of RANK receptor on osteoclasts?
Promotes differentiation
53
What happens when RANKL binds to RANK?
Promotes osteoclast differentiation
54
What secretes OPG?
Osteoblasts
55
What is the function of osteoclast precursors?
To differentiate into active osteoclasts
56
What is the effect of blocking RANKL?
Turns off or reduces osteoclast activity
57
What type of molecule is Denosumab?
Monoclonal antibody
- Mimics the effect of OPG
58
What does Denosumab bind to?
RANKL
59
Can Denosumab bind to osteoclasts?
No
60
What is the overall effect of Denosumab?
Prevents bone loss
- Reduces the number of osteoclasts differentiated
61
What are the three hormones that control plasma calcium levels?
PTH, Calcitriol, Calcitonin
62
What are the three primary target sites of these hormones?
Bones, kidneys, digestive tract
63
Where is PTH released from?
Parathyroid glands (chief cells)
64
What is the main function of PTH?
Increases plasma Ca2+ concentration
65
What stimulates the release of PTH?
Low plasma Ca2+
66
Why are the parathyroid glands essential for life?
Calcium is essential for life
67
Where are the parathyroid glands located?
Posterior view, stuck to thyroid gland
68
What happens if the parathyroid glands are removed?
It is fatal
69
How do the parathyroid glands sense calcium levels?
Sensed by glands
70
What happens to PTH levels when calcium levels are around 1.3 mM
Very little PTH in blood
71
What happens to PTH levels as calcium decreases below 1.2 mM?
Huge spike in PTH
72
What does the graph indicate about parathyroid cells' sensitivity?
Exquisitely sensitive to changes
- Parathyroid cells are very sensitive to calcium levels
73
What is the primary goal of the parathyroid glands when calcium levels drop?
To correct it
74
What type of receptor is used to monitor extracellular calcium?
Large G protein-coupled receptor
75
What happens when calcium is bound to the calcium-sensing receptor?
Keeps PTH from being released
76
What is the role of Vitamin D3 receptor in this process?
Reduces need for PTH
77
What is the effect of calcium binding on PTH synthesis and secretion?
Inhibits pathways
78
What happens to the pathways when there is no calcium bound to the receptor?
They disengage
79
What is the main function of the calcium-sensing receptor?
Monitor extracellular calcium
80
What is the ultimate effect of the pathways when calcium is bound to the receptor?
Reduced PTH synthesis
81
What is the role of the nucleus in this process?
Increases Vitamin D3 receptor
82
What are the two primary organs that PTH acts on directly?
Bone and kidney
83
What does PTH do to RANKL and OPG in bone?
Increases RANKL, decreases OPG
84
What is the effect of PTH on calcium reabsorption in the kidneys?
Increases reabsorption
85
What does PTH stimulate in the kidneys?
Calcitriol synthesis
86
What is the overall effect of PTH on plasma calcium levels?
Increases plasma calcium
87
What is the role of osteoblasts in PTH's action on bone?
Acts on osteoblasts
88
What is the destination of calcium that is reabsorbed in the kidneys?
Into the bloodstream
89
What does PTH increase in osteoblasts?
cAMP
90
Increased cAMP leads to what changes in expression?
Increased RANKL, decreased OPG
91
What is the result of increased RANKL?
More osteoclasts are formed
92
What process is promoted by osteoclast formation?
Bone resorption
93
What is the overall effect of PTH on bone?
Bone resorption
94
What does reducing OPG lead to?
More active osteoclasts
95
What is the role of osteoblasts in this process?
Stimulate signaling pathways
96
What is the active form of Vitamin D?
Calcitriol
97
Which organs are crucial for calcitriol development?
Skin, liver, kidney
98
What does Vitamin D go through to become calcitriol?
Multiple enzymatic steps
99
What does calcitriol target to increase serum calcium?
Intestine, bone, kidney
100
What is the initial precursor for Vitamin D in the skin?
7-dehydrocholesterol
101
What is required to convert the precursor into cholecalciferol?
Sunlight
102
Where does the first conversion of cholecalciferol occur?
In the liver.
103
What enzyme is activated by PTH in the kidneys?
The enzyme that converts 25-hydroxycholecalciferol to calcitriol in the kidney
104
What is the active form of Vitamin D?
Calcitriol
105
What is the main function of calcitriol in the small intestine?
Increases calcium uptake
106
What other actions does calcitriol have?
Renal calcium reabsorption and mobilization from bone
107
What helps with calcium absorption when you eat?
Vitamin D3 hormone
108
What is the role of Vitamin D3 hormone?
Helps with absorption.
109
What type of hormone is calcitriol?
Lipophilic
110
What receptor does calcitriol bind to in the cell?
Vitamin D nuclear receptor (VDR)
111
What does VDR form a heterodimer with?
Retinoic acid receptor (RXR)
112
Where does the VDR-RXR complex go after binding?
To the nucleus
113
What does the complex find in the nucleus?
Vitamin D response element
114
What does the binding to the response element increase?
Expression of mRNA
115
What happens to calcium levels in the blood during a deficit?
They decrease
116
What hormone is released when calcium levels are low?
Parathyroid hormone (PTH)
117
What is the effect of PTH on bone?
It causes the release of calcium
118
How does PTH affect calcium loss in urine?
It decreases calcium loss
119
What hormone increases calcium absorption from the intestine?
Calcitriol
120
What is the combined effect of PTH and calcitriol?
Increased blood calcium
121
What is the role of bone in correcting calcium deficit?
Releases calcium into the blood
122
How does the kidney contribute to correcting calcium deficit?
By reabsorbing calcium
123
What happens to phosphate when bone is broken down?
It is released
124
How does PTH affect phosphate reabsorption in the kidney?
It decreases reabsorption
125
What is the effect of calcitriol on phosphate absorption in the intestine?
It increases absorption
126
How does calcitriol affect phosphate reabsorption in the kidney?
It increases reabsorption
127
What is the role of calcitriol in phosphate control?
To help make bone
128
What is the role of PTH in phosphate control?
To release calcium from bone
129
Where is calcitonin secreted from?
C cells of the thyroid gland
130
What type of hormone is calcitonin?
Peptide hormone
131
What triggers the release of calcitonin?
High plasma calcium
132
What kind of receptors do C cells have?
Calcium-sensing receptors
133
What is another name for C cells?
Parafollicular cells
134
Do C cells release thyroid hormones?
No
135
Where are the parathyroid glands located?
Posterior view, facing back body
136
What is the overall effect of calcitonin on calcium levels?
"Tones down" calcium levels
137
What is a potential role of calcitonin in humans?
Protect the skeleton during pregnancy and lactation
138
How does calcitonin affect osteoclast activity?
Reduces activity
139
What is the effect of calcitonin on bone resorption?
Inhibits bone resorption
140
How does calcitonin affect osteoblasts?
Stimulates them to deposit calcium
141
What happens to calcium in the kidneys due to calcitonin?
Inhibits reabsorption
142
What condition occurs when there is too much calcium?
Hypercalcemia
143
What are some symptoms of hypercalcemia?
- GROANS: Constipation
- MOANS: Fatigue, lethargy, depression
- BONES: bone pain
- STONES: kidney stone
- Psychiatric OVERTONES: Depression and confusion, weakness
144
What condition occurs when there is too little calcium?
Hypocalcemia
145
What are some symptoms of hypocalcemia?
- C = Convulsions
- A = Arrhythmias
- T = Tetany
- S = Spasms, Seizures, & Stridor
