Lecture 3 - Ca and Mg

Question 1

What are some processes which Ca is involved in?

Answer 1

muscle contraction
nerve conduction
hormone release
blood coagulation.

Question 2

What is the FUNCTION of ca

Answer 2

Calcium assists in maintaining all cells and connective tissues in the body and regulating mitotic transition and cell division.
Essential component in the production of enzyme and hormones that regulate digestion, energy, and fat metabolism.
Neurotransmitter release
Homeostasis-activation of clotting enzyme is the plasma
Preserving bone density- construction, formation and maintenance of bone and teeth

Question 3

Factors on Ca conc

Answer 3

1. Change in plasma protein con
2. Chnages in anions
3. Acid-base abnormality.

Question 4

How is Ca regulated?

Answer 4

bidirectional Ca transport across the plasma membrane of cells and by the membranes of intracellular organelles

Question 5

What systems regulate Calcium balance?

Answer 5

Principle organ systems:
Intestine
Bone
Kidney

Hormones:
Parathyroid hormone (PTH)
Vitamin D
Calcitonin

Question 6

Draw a diagram of how Ca is regulated

Answer 6

Lecture slides

Question 7

Role of PTH

Answer 7

Stimulates renal reabsorption of calcium
Inhibits renal reabsorption of phosphate
Stimulates bone resorption
Inhibits bone formation and mineralization
Stimulates synthesis of calcitriol

Question 8

What is the net effect of PTH

Answer 8

Increase serum Ca, decrease serum phosphate

Question 9

What happens to PTH if there is LOW serum Ca

Answer 9

Low serum [Ca+2] = Increased PTH secretion

Question 10

Role of VITAMIN D

Answer 10

Stimulates GI absorption of both calcium and phosphate

Stimulates renal reabsorption of both calcium and phosphate

Stimulates bone resorption- release calcium from bone matrix

Question 11

Net effect of calcitriol

Answer 11

Increase serum Ca and Phosphate

Question 12

Role of calcitonin

Answer 12

is involved in helping to regulate levels ofcalciumand phosphate in the blood, opposing the action of parathyroid hormone.

It inhibits the activity of osteoclasts, which are the cells responsible for breaking down bone. When bone is broken down, the calcium contained in the bone is released into the bloodstream.

It can also decrease the resorption of calcium in thekidneys, again leading to lower blood calcium levels.

Question 13

What are the different forms of Calcium?

Answer 13

45% in ionized form (the physiologically active form)
45% bound to proteins (predominantly albumin)
10% complexed with anions (citrate, sulfate, phosphate)

Question 14

What is HYPERcalcemia?

Causes?

Answer 14

is a condition in which the calcium level in your blood is above normal.

overactive parathyroid glands.
cancer
certain other medical disorders
some medications taking too much of calcium and vitamin D supplements.

Question 15

What is HYPOcalcemia?

Causes?

Answer 15

is due to the absence or impaired function of the parathyroid glands or impaired vitamin-D synthesis.

Chronic renal failure
decreased vitamin-D synthesis

Question 16

Magnesium, intracelluar or extracellualr?

Answer 16

intracelluar

Question 17

Where is the most Mg found?

Answer 17

60% in the bone

Question 18

What are the determinans on Mg Homeostasis?

Answer 18

gastrointestinal absorption and renal excretion

Question 19

Causes of hypomagnesemia

Answer 19

GI secretions in large amounts

Malnutrition with low dietary intake of Mg

Renal losses from primary renal disorders (decreased tubular reabsorption of Mg from damaged kidneys) or secondary causes

Redistribution of Mg into cells (Insulin)

Pregnant women have been found to be Mg depleted

Drugs causing Mg wastage

Endocrine disorders

Question 20

Physcial findings for Hypomagenesemia

Answer 20

Neuromuscular irritability

• Hyperactive deep tendon reflexes
• Muscle cramps
• Muscle fibrillation
• Dysarthria and dysphagia from esophageal dysmotility

CNS hyperexcitability

• Irritability and combativeness
• Disorientation
• Psychosis
• Vertigo, and seizures

Question 21

If there is low serum Mg, does this indicate hypomag? Why?

Answer 21

Body stores of magnesium may be depleted markedly before the serum level drops, so a deficiency of Mg is clearly present if the serum level is low

Because extracellular magnesium is protein bound, the patient’s protein status is an important consideration in interpreting magnesium levels

Hypocalcemia is caused by magnesium depletion, but the reason is not known

Hypophosphatemia has been found in patients with hypomagnesemia

Question 22

What is the relationship between Hypomagnesemia & Hypokalemia

Answer 22

Hypomagnesemia can cause Hypokalemia

Mg is a cofactor for the Na+/K+ATPase
Without Mg, cellular homeostasis cannot be maintained and K+ loss occurs in the kidneys

HYPOKALEMIA CANNOT BE CORRECTED UNLESS HYPOMAGNESEMIA HAS BEEN CORRECTED

Question 23

Hypocalcemia and chronic renal failure
Characteristic Symptoms
Impairs what processes?

Answer 23

is due to the absence or impaired function of the parathyroid glands or impaired vitamin-D synthesis.

Chronic renal failure is also frequently associated with hypocalcemia
due to decreased vitamin-D synthesis as well as hyperphosphatemia and skeletal resistance to the action of parathyroid hormone (PTH).

Characteristic symptoms of hypocalcemia are latent or manifest muscle cramps and osteomalacia.