Calcium & Phosphate Homeostasis

Question 1

Hypocalcemia

Answer 1

• Low extracellular Ca2+
• Reduces the activation threshold for Na+ channels –> easier to evoke AP
• Results in increased membrane excitability (spontaneous APs)
• Generation of spontaneous APs is the basis for hypocalcemic tetany (spontaneous muscle contractions due to low EC Ca2+)
• Produces tingling and numbness (on sensory neurons) and spontaneous muscle twitches (on motor neurons and muscle)

Question 2

Hypercalcemia

Answer 2

• Opposite of hypocalcemia mechanism (decrease in membrane excitability)
• Nervous system becomes depressed and reflex responses are slowed

Question 3

Symptoms of Hypocalcemia

Answer 3

• Hyperreflexia
• Spontaneous twitching
• Muscle cramp
• Tingling
• Numbness

Question 4

Indicators of Hypocalcemia

Answer 4

• Chvostek Sign: twitching of the facial muscles elicited by tapping
• Trousseau Sign: carpopedal spasm upon inflation of a BP cuff

Question 5

Symptoms of Hypercalcemia

Answer 5

• Decreased QT interval
• Constipation
• Lack of appetite
• Polyuria (excessive urination)
• Polydipsia (excess thirst)
• Muscle weakness
• Hyporeflexia
• Lethargy
• Coma

Question 6

If increase in plasma protein concentration (albumin), then have ___ in total Ca2+ concentration.

Answer 6

Increase

Question 7

Change the fraction of Ca2+ complexed with a ions – if increase phosphate concentration then ____ in ionized (free) Ca2+ concentration

Answer 7

Decreased

Question 8

In order to maintain Calcium homeostasis, ___ must get rid of same amount of Ca2+ that ___ takes in

Answer 8

• Kidneys
• GI