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Endocrine Physiology > Vephy M4 Part 1 > Flashcards

Vephy M4 Part 1 Flashcards

1
Q

Identify the major hormonal regulator of the reabsorption of phosphate

A

PTH

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2
Q

Mode of action of PTH to phosphte

A

Decreases the rate of tubular reabsorption and increases the renal excretion of phosphate

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3
Q

Other hormones
which inhibit Na/Pi cotransport

A
  1. Calcitonin
  2. Atrial natriuretic peptide
  3. Epidermal growth factor
  4. Transforming growth factors α and β
  5. Parathyroid hormone-related protein
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4
Q

Other hormones
which stimulate Na/Pi cotransport by renal epithelial cells

A
  1. insulin
  2. growth hormone,
  3. insulin-like growth factor-1
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5
Q

rate of reabsorption of renal phosphate is dependent of?

A

availability of Na+

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6
Q

rate of reabsorption of renal phosphate is regulated by?

A

need of the animal for phosphate

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7
Q

Renal excretion of phosphate is regulated by?

A
  1. glomerular filtration rate
  2. maximal rate of tubular reabsorption
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8
Q

Which diet increase saliva production and the total salivary secretion of phosphate

A

high fiber

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9
Q

What are the effects of increased endogenous salivary secretion of phosphate?

A
  1. increased intestinal absorption
  2. increased fecal losses and results in the net loss of phosphate
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10
Q

Ruminants with this kind of diet use this
endogenous fecal loss of phosphate as the principal mechanism to regulate phosphate excretion

A

roughage diet

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11
Q

ruminants given with this feed excrete more phosphate in the urine

A

concentrated diet

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12
Q

Identify the important determinants of phosphate excretion in
ruminants

A
  1. quantity of saliva
  2. regulation of the phosphate concentration in saliva
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13
Q

buffer volatile fatty acids and are nutrients for microorganisms in the rumen

A

Phosphate anions

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14
Q

Parotid saliva in these species contains phosphate at levels of 16-40 mmol/L

A

ruminants

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15
Q

An enzyme present in ruminants in which release the phosphate from the sugar moiety

A

Phytase

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16
Q

Give two nutrients in the diet that antagonize phosphate absorption

A

aluminum & magnesium

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17
Q

Diets with high content of these two substances raise the requirement for phosphorus

A

calcium & fat

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18
Q

Approximately 60-70% of dietary phosphate is absorbed from the intestine by?

A
  1. active transport (Na/phosphate
    cotransporter)
  2. passive diffusion
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19
Q

In ruminants, instead of sodium, the Na/phosphate
cotransporter is coupled with?

A

H+

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20
Q

essential mineral component of the skeleton and plays a central role in maintaining the homeostasis of vertebrate animals

A

calcium

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21
Q

involved in a wide variety of physiological processes
including muscular contraction, blood coagulation, enzyme activity, neural excitability, hormone secretion,
and cell adhesion

A

ionized calcium

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22
Q

Endocrine factors that influence levels of calcium in the body

A

(i) parathyroid hormone
(ii) calcitonin
(iii) calcitriol

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23
Q

bioactive vitamin D
metabolite derived from cholecalciferol (vitamin D3)

A

calcitriol (1,25-dihydroxycholecalciferol; 1,25-dihydroxyvitamin D)

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24
Q

Calcitonin secreted by the which tissues of the thyroid gland

A

parafollicular or C-cells

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25
Q

synthesized and released by the chief cells of the parathyroid glands

A

PTH

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26
Q

Disruption of the normal regulation of calcium balance in animal results to?

A

hypercalcemia or hypocalcemia

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27
Q

What are the pathological effects associated with abnormal levels of calcium in the body?

A
  1. calcification of vital organs & soft tissue
  2. rickets
  3. osteoporosis
  4. reproductive disorders (puerperal tetany, milk fever)
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28
Q

99% of the calcium of the body is present in the inorganic matrix of bone as

A

hydroxyapatite

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29
Q

Aside from the hydroxyapatite, where are most of the remaining calcium sequestered?

A

plasma membrane and endoplasmic reticulum of cells

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30
Q

biologically active form of calcium

A

Ionized form (Ca2+)

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31
Q

these species limit and regulate Ca2+ absorption from the intestinal tract, skin, or gills

A

fishes

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32
Q

hormones that reduce the concentration of Ca2+ in the serum

A

calcitonin and stanniocalcin

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33
Q

Fishes primary role of reducing the loss of body Ca2+ and maintaining serum Ca2+

A

lack of parathyroid glands

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34
Q

Identify the important regulators of total body calcium in terrestrial vertebrates

A

parathyroid glands and the kidneys

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35
Q

Give the two primary functions of calcium

A
  1. structural integrity of bones and teeth
  2. as a messenger or regulatory ion
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36
Q

Influx of Ca2+ into cells can: (2)

A
  1. regulate cellular function by interactions with intracellular calcium-binding proteins (e.g., calmodulin) and
    calcium-sensitive protein kinases
  2. stimulate biologic responses such as neurotransmitter release, contraction, and secretion
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37
Q

Present in cell membrane of chief cells of parathyroid glands and renal epithelial cells that regulate cellular functions once combined with Ca2+

A

G-protein-linked Ca2+-sensing receptor

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38
Q

Identify the 3 forms of extracellular and serum calcium

A

1.) ionized

2.) complexed to anions such as citrate, bicarbonate, phosphate, or lactate (5% of total calcium)

3.) protein-bound

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39
Q

which form of calcium dependent on the pH of the serum and is principally bound to negatively- charged sites on albumin

A

protein-bound

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40
Q

compose the ultra-filterable fraction of Ca2+ and represent the fraction
that is present in the glomerular filtrate

A

ionized and complexed Ca2+

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41
Q

What is the concentration of ionized Ca2+ in the serum in most domestic animals?

A

1.25-1.6 mmol/L (5.0 – 6.4 mg/dl)

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42
Q

Form of calcium that enters the glomerular filtrate and reabsorbed by the renal tubules

A

Ionized and complexed calcium

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43
Q

What are the factors by which kidney s reabsorb approximately 40-fold more calcium than is absorbed by the intestinal tract ?

A
  1. high degree of blood flow
  2. ultrafiltration in the glomerulus
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44
Q

Which part of the nephron 70% of filtered calcium is reabsorbed

A

proximal convoluted tubules

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45
Q

Part of nephron that absorbs about 20% of the filtered calcium

A

thick ascending loop of Henle

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46
Q

10% of the calcium is reabsorbed by which part of the nephron

A

distal convoluted tubule

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47
Q

Give the principal stimulator of calcium reabsorption in the distal
convoluted tubules

A

PTH

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48
Q

Reabsorption of calcium in the distal convoluted tubule is an active transcellular process and requires what?

A

calcium channels

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49
Q

an intracellular calcium-binding proteins

A

calbindins

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50
Q

Give the 3 measurements of calcium excretion in animals

A
  1. calcium and calcium-creatine (Ca/Cr) ratio in the urine
  2. fractional calcium excretion
  3. 24-hour calcium excretion
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51
Q

Name the species that excrete larger amounts of calcium in the urine

A

Horses

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52
Q

a better indicator of calcium excretion because it corrects for errors in
timing of urine collections, concentration or dilution

A

Ca/Cr ratio of the urine

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53
Q

best measured in a fasting animal to eliminate the role of dietary
calcium on renal calcium excretion

A

Fractional calcium excretion

54
Q

Identify the major sources of urinary calcium when there is little gastrointestinal absorption of calcium

A
  1. calcium released from bone
  2. obligate renal calcium loss
55
Q

good measurement of daily calcium loss and may be used to
investigate calcium balance

A

24-hour calcium excretion

56
Q

2 components of calcium absorption from the intestinal tract

A

(a) saturable or transcellular transport
(b) non-saturable or intercellular (paracellular) transport

57
Q

associated with absorption rates of up to 95% of intestinal absorption of calcium

A

Low-calcium diets

58
Q

high-calcium diets have absorption rates of about _____

A

40%

59
Q

percentage of intestinal absorption of calcium is proportional to ___?

A

dietary intake

60
Q

Diets deficient in calcium are associated with normal serum calcium concentrations due to compensation by? (3)

A

(i) bone resorption stimulated by parathyroid hormone

(ii) renal calcium reabsorption

(iii) increased synthesis of 1,25-dihydroxyvitamin D

61
Q

Saturable transport is dependent of?

A

Vitamin D

62
Q

Where does saturable transport occurs predominantly

A

duodenum, less on cecum and colon

63
Q

1,25-dihydroxyvitamin D in the intestinal epithelial cell increases the expression of these calcium binding protein

A

calbindin

64
Q

What stimulates transcellular transport of Ca2+?

A

vitamin D (1, 25-dihydroxyvitamin D)

65
Q

occurs throughout the small intestine and is the main mechanism for calcium absorption in animals deficient in vitamin D

A

non-saturable calcium transport

66
Q

Non-saturable Ca2+ transport is
dependent on the?

A

luminal Ca2+

67
Q

Factors which increase intestinal calcium absorption, directly or indirectly, due to stimulation of 1,25-
dihydroxyvitamin D synthesis, include:

A
  1. parathyroid hormone
  2. growth hormone
  3. testosterone
  4. estrogen
  5. furosemide
68
Q

Factors that reduce intestinal absorption of calcium

A
  1. Glucocorticoids
  2. thyroid hormones
  3. chronic acidosis
  4. luminal conditions that induce the complexation of Ca2+
69
Q

Two sources of Ca2+ in bone that can enter the circulation

A
  1. readily mobilizable calcium salts in the ECF
  2. hydroxyapatite crystals that require digestion by osteoclasts
70
Q

source of calcium in bones that is present in small amounts, it plays a role of fine regulation of serum calcium

A

Mobilizable calcium ion

71
Q

An animal with significant need for calcium from bone, must come from?

A

osteoclastic resorption of hydroxyapatite crystals

72
Q

In ______ _______, stable balance between calcium deposition associated with bone formation and calcium release

A

adult animals

73
Q

In ______ _______, bone has a positive calcium balance due to the relative excess of bone formation

A

young animals

74
Q

Conditions associated with bone resorption and the release of calcium from bone which contributes to the development of hypercalcemia

A
  1. Humoral hypercalcemia of malignancy
  2. osteolytic bone metastasis
  3. primary hyperparathyroidism
75
Q

responsible for sensing serum Ca2+ concentration

A

Ca2+ receptor

76
Q

90% of phosphate in the mammalian body is present as

A

hydroxyapatite

77
Q

How many % of phosphate is present in soft tissues

A

10%

78
Q

major intracellular anion existing in inorganic form

A

phosphate

79
Q

Phosphate plays an integral role in metabolic processes such as (4)

A
  1. energy metabolism
  2. delivery of O2 to tissues
  3. muscle contraction
  4. skeletal integrity
80
Q

What is the major regulators of the phosphate concentration in the serum, in nonruminant animals?

A

kidneys

81
Q

80% of inorganic phosphate in the serum is in what form

A

dibasic form (HPO4)

82
Q

20% of inorganic phosphate in the serum is in what form

A

monobasic form (H2PO4)

83
Q

range of Serum Pi in adult animals

A

2.5-6.0 mg/dl (0.8-1.9 mmol/L)

84
Q

unrealiable indicator of body stores and may be higher in growing animals than in adults

A

serum phosphate

85
Q

In these species, external
parathyroid gland is located a considerable distance and cranial to
the thyroid gland

A

cattle & sheep

86
Q

secrete and release parathyroid hormone

A

chief cells

87
Q

Shape of inactive chief cells

A

cuboidal

88
Q

do not have an active function in the biosynthesis of parathyroid hormone

A

oxyphils

89
Q

increase in numbers in humans in response to long-term stimulation of
the parathyroid glands

A

oxyphil cells & transitional cells

90
Q

Active PTH is packed by which cell organelles

A

Golgi apparatus

91
Q

Identify the phases wherein concentration of calcium exerts an effect on chief cells

A

secreting and involuting phases

92
Q

speed up the rate of secretion and shorten the resting phase of PTH

A

Low levels of intra- and extracellular calcium

93
Q

suppress the rate of PTH secretion and lengthens the resting phase of the
secretory cycle

A

high intra- and extracellular levels of calcium

94
Q

these species have consistently more PTH secretory granules than man and other animals

A

bovine parathyroid cells

95
Q

The correct term for release of insulin from secretory granules in the cells of the pancreatic islet

A

emiocytosis

96
Q

Why do parathyroid glands have a unique mechanism for feedback
control?

A

due to the cellular response to the concentration of calcium and to a lesser extent of magnesium ion

97
Q

What is the influence of serum levels of ionized calcium and interaction with the Ca2+-sensing receptors on chief cells?

A

formation of an inverse sigmoidal-type of relationship between serum Ca2+ and PTH concentrations

98
Q

What are the major inhibitors of PTH synthesis and secretion?

A
  1. increased serum levels of Ca2+
  2. 1, 25-dihydroxyvitamin D.
99
Q

What happens if there is elevation of blood calcium by IV infusion?

A

There is rapid and pronounced reduction in circulating levels of immunoreactive parathyroid hormone.

100
Q

What is likely to happen if the blood
calcium is lowered by infusion of EDTA?

A

brisk and substantial increase in the level of immunoreactive PTH

101
Q

True or False. Concentration of blood phosphate direct regulatory influence on the synthesis and secretion of PTH.

A

False. Because it has no direct regulatory influence on the synthesis and secretion of PTH

102
Q

An elevated blood phosphorus level may lead indirectly to parathyroid stimulation, and this is due to?

A

High levels of phosphorus can lower calcium levels in the body.

103
Q

This ion has an effect on secretory
rate of parathyroid hormone similar to that of calcium, but the effect is not equipotent to that of calcium.

A

Magnesium [Mg2+]

104
Q

Why does Magnesium ion has reduced potency than Ca2+ in terms of PTH stimulation?

A

Because magnesium ion has reduced binding affinity for the Ca2+
-sensing membrane receptors on chief cells.

105
Q

True or False. Calcium ion only controls the rate of biosynthesis and secretion of parathyroid hormone, while magnesium control the other metabolic and intracellular degradative processes occur within chief cells.

A

False. Biosynthesis, secretion of PTH and other metabolic processes of chief cells are controlled by Calcium.

106
Q

It is the principal hormone involved in the minute-to-minute, fine regulation of blood calcium in mammals

A

PTH

107
Q

Give at least five most important biologic effects of PTH

A
  1. elevate the blood concentration of calcium.
  2. decrease the blood concentration of phosphorus.
  3. increase the urinary excretion of phosphorus by a decreased rate
    of tubular reabsorption.
  4. increase the tubular reabsorption of calcium.
  5. increase the rate of skeletal remodeling and the net rate of bone
    reabsorption.
108
Q

facilitates the movement of calcium from bone to the extracellular fluid for the fine adjustment of the calcium concentration in the blood

A

Osteocyte-osteoblast “pump”

109
Q

primarily responsible for the long-term
actions of PTH on increasing bone resorption and overall bone remodeling

A

Osteoclasts

110
Q

a complex, multistep, process that involves the activation of multiple genes and the action of multiple hormones

A

bone resorption

111
Q

a membrane-bound protein on osteoblasts that serves as a common mediator for osteoclastic bone resorption

A

RANK ligand or RANKL (Receptor Activator of Nuclear factor-kappa B Ligand)

112
Q

RANK ligand or RANKL was initially called as?

A

osteoclast differentiation factor or osteoprotegerin ligand

113
Q

novel member of the TNF receptor superfamily that is produced by cells of the osteoblast lineage and is a negative regulator of bone resorption

A

osteoprotegerin / decoy receptor

114
Q

True or False. When soluble
osteoprotegerin binds to the RANK receptor, it prevents the RANK ligand from binding and activating the receptor.

A

True.

115
Q

leads to osteopetrosis associated with decreased osteoclast formation and function

A

Overexpression of osteoprotegerin (OPG)

116
Q

alterations in this ratio may
be a major cause of bone loss in metabolic disorders such as estrogen-deficiency or glucocorticoid- excess

A

RANKL; OPG

117
Q

an organic component phagocytized
by osteoclasts and transported across the cell and released into the ECF

A

hydroxyproline

118
Q

site of action of PTH on the tubular reabsorption of phosphate has been localized to this region

A

PCT

119
Q

True or False. PTH leads to the increased urinary excretion of potassium, sodium, bicarbonate, Camp, and amino acids

A

True.

120
Q

True or False. Capacity of PTH to enhance the renal reabsorption of calcium is of considerably more important than its effect phosphaturia.

A

True. Renal reabsorption of calcium is of considerably more important in the maintenance of calcium homeostasis

121
Q

True or False. Urinary excretion of magnesium and ammonia, and the titratable acidity of the urine are increased by PTH.

A

False. It is decreased by PTH.

122
Q

promotes the absorption of calcium from the gastrointestinal tract in animals

A

PTH

123
Q

The major organ for the degradation of PTH

A

kidney

124
Q

PTH half life

A

less than 5 mins

125
Q

PTH is removed from the circulation by?

A

endopeptidases in hepatic Kupffer cells

126
Q

plays a central role in the pathogenesis of humoral hypercalcemia of malignancy

A

Parathyroid hormone-related protein (PTHrP)

127
Q

True or False. PTHrP is not strictly a calcium-regulating hormone.

A

True.

128
Q

Function of PTHrP is likely as an _________ regulatory factor

A

autocrine or paracrine

129
Q

play a role in stimulating the transport of calcium by alveolar epithelial cells from serum to milk

A

PTHrP

130
Q
A

Endocrine Physiology (5 decks)

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