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Human Physiology (BIOL 2410/2420) > Calcium regulation > Flashcards

Calcium regulation Flashcards

1
Q

Where is calcium found in the body?

A

99% Bone
0.9% intracellular
0.1% ECF bound to proteins or free form

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2
Q

What are some of the functions of calcium?

A
  1. Neuromuscular excitability
  2. Required to stimulate secretion of substances
  3. Cell-Cell integrity of tight junctions
  4. Cofactor for clotting blood
  5. Required for structural form of bone and teeth
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3
Q

How is calcium absorbed in the extracellular fluid, bone, kidney, and cell?

A
  1. From diet, calcitriol, PTH, and prolactin pulls Ca++ from intestine into extracellular fluid
  2. Calcitonin calcifies ECF Ca++ into bone, while parathyroid hormone/calcitriol/cortisol returns it to ECF
  3. Filtration from blood allows Ca++ take up into kidney, some are reabsorbed via PTH and some leave via urine
  4. In the cell, Ca++ goes in via electrochemical gradient and leaves via active transport
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4
Q

What is bone made of?

A

Hydroxyapatite crystals (precipitate of 3Ca++ and 2PO4—) between a collagen matrix.

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5
Q

What is the difference between osteocyte, osteoblasst, osteoclasts?

A

Osteocyte: mature bone cells

Osteoblast: deposite collagen matrix

Osteoclast: break bone to form Ca++

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6
Q

What is the parathyroid hormone?

A

PTH is produced in the parathyroid glands on the thyroid and has an extremely sensitive negative relationship with plasma Ca++

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7
Q

How is vitamin D3 created?

A

Cholecalciferol is given OH2 by enzyme regulated by PTH pt at iPr group on top right hand side, and on the hexane on the bottom to form calcitriol

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8
Q

What is the fast and slow rate of exchange of calcium from the bone into the plasma?

A

Fast: exchange from bone fluid’s pool of Ca++ into blood vessel

Slow: dissolution of bone into bone fluid and exchange into blood vessel

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9
Q

How does PTH influence the kidney?

A

Increase in PO4 urination = decrease in blood PO4 = increase in solubilisation of bone = increase in bone fluid calcium

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10
Q

What is a secosteroid?

A

Steroid derived from cholesterol

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11
Q

How does vitamin D aid in the take up of Ca+ from the gut?

A
  1. Ca++ enters apical side of gut epithelium through TRPV5/6 via electrochemical gradient
  2. Calbindin D binds to Ca++ and carries it to basolateral side of enterocyte to drop it off at PMCA1 and NCX1
  3. PMCA1 exchanges ATP to move Ca++ into interstitial space, NCX1 moves Ca++ into interstitial space via antiport with Na+
  4. 1,25(OH2)2D3, aka calcitriol, enters gut nucleus and promotes synthesis of TRPV5/6, calbindin D, NCX 1 and PMCA1
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12
Q

How is vitamin D regulated with PTH

A
  1. Sunlight converts 7-dehydrocholesterol in skin to Vitamin D3 (Cholecalciferol)
  2. In the liver, Cholecalciferol is converted to 25-OH-D3 or Calcidiol.
  3. Calcidiol moves to kidney and PTH influences its conversion to 1,25-(OH2)-D3 or calcitriol.
  4. Calcitriol promotes uptake of Ca2+ from the gut, bone and kidney.
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12
Q

What are the cells in the parathyroid gland?

A

Cuboidal follicular cells: line the thyroid follicles and produce and release thyroid hormones

Colloid: thyroglobulin that fills the lumen of the follicles in the gland.

Sinusoidal capillaries: molecule exchange

Parafolicular cells: produce calcitonin

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13
Q

What does the parathyroid secrete to low plasma Ca2+ and high plasma Ca2+

A

Low plasma Ca++: increase in PTH

High plasma Ca++: increase in calcitonin

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13
Q

Where are osteoblasts and osteoclasts derived from?

A

Osteoblasts: stromal cells in bone marrow

Osteoclasts: Macrophages in bone marrow

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13
Q

What main messengers do osteoblasts produce and what are their functions?

A

RANKL: act as ligands for macrophages triggering differentiation to osteoclasts and survival of osteoclasts, which decreases bone mass

Osteoprotegerin (OPG): production stimulated by estradiol; acts as RANKL inhibitor which decreases osteoclast action and increases bone bass

14
Q

What is osteoporosis?

A

Reduced bone mineral density prevalent in pre and post menopausal woman. 1% bone mass is lost every year

15
Q

What is therapy for osteoperosis?

A
  1. Exercise
  2. Ca++ supplements
  3. Hormone replacement therapy
  4. Calcitonin
  5. Selective estrogen receptor modulators (SERMS)
  6. activators of nongenotropic estrogen like signaling (ANGELS)
16
Q

What are the two types of thyroid hormones and where are they made?

A

Tetraiodothyronine (T4) and Triiodothyronine (T3) are dervied from thyroglogulin in the follicular cells and colloid of the thyroid gland.

17
Q

What are the parts of a thyroid hormone?

A

Iodinated outer phenyl ring, ether link, and Iodinated inner tyrosyl ring.

18
Q

How to classify the three types of thyroid hormone?

A

T4: all rings are iodinated

T3: first ring is half Iodinated, second ring is fully iodinated

Reverse T3: first ring is fully iodinated, second ring is half iodinated.

19
Q

How does TSH stimulate

A
  1. TSH from pituitary enters thyroid cell and causes signal cascade (cAMP) necessary for thyroglobulin synthesis from DNA, which is released into the colloid space.
  2. Na+/I- brings in iodide which through peroxide reeaction becomes inorganic I which is released into the colloid space.
  3. Inorganic I and thyroglobulin undergo oxidative coupling to form DIT and MIT which combine in certain sequences to form T4 or T3.
  4. T4 and T3 are taken up via endocyrosis and released into the blood to target tissues
20
Q

How does thyroid hormone become deiodinated?

A

Type I deiodinase: deiodinates reverse T3

Type II deiodinase: deiodinates only the outer ring (T4 toT3)

Type II deiodinase: deiodinates only the inner ring (T4 to reverse T3)

21
Q

What is the calorigenic action of thyroid hormone?

A

Regulator of basal metabolic rate and conversion of food energy to heat and storage

22
Q

What is the sympathomimetic/cardiovascular effect of thyroid hormone?

A

Promotes role of catecholamines which increase heart rate and stroke volume which increases cardiac output.

23
Q

What is the difference between chronotropic and inotropic effects

A

Chronotropic effects are changes to the heart rate or rhythm

Inotropic effects change the force or energy of heart muscle contractions

24
Q

How does the thyroid hormone promote growth?

A

In synergism with growth hormones and somatomedins in normal growth and neural development.

25
Q

What is goiter?

A

Overstimulation of thyroid gland due to hypothyroidism or hyperthyroidism. Occurs when

26
Q

What are difference between hypothyroidism and hyperthyroidism?

A

Hypothyroidism: low basal metabolic rate, slow pulse, low body temp, weight gain

Hyperthyroidism: high basal metabolic rate, rapid pulse, increased body temp, weight loss

27
Q

What is melatonin?

A

Primary hormone synthesized by tryptophan and released in scotophase (dark) and photophase (light)

28
Q

What is the suprachiasmatic nucleus?

A

interaction between PER genes and CLOCK proteins that link the pineal and optic tract

29
Q

How does photophase inhibit pineal gland?

A
  1. Light hits melanopsin protein in retina
  2. sends sensory information to the superchiasmatic nucleus to the brain stem and down to the spinal cord.
  3. From the spinal cord, the preganglionic neuron synapses with the superior cervical ganglion
  4. Postganglionic sympathetic neuron inhibits noradrenergic stimulation of the pineal gland which reduces melatonin secretion

Human Physiology (BIOL 2410/2420) (15 decks)

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