Tetany

Tetany

Q. 1 In tetany the increased membrane excitability is caused by:
 A Decreased release of  inhibitory neurotransmitter from nerve terminals
 B Depolarization of  the nerve and  muscle membranes
 C Spontaneous   release   of   calcium   from   the sarcoplasmic reticulum
 D Activation of sodium channels at more negative membrane potentials
Q. 1 In tetany the increased membrane excitability is caused by:
 A Decreased release of  inhibitory neurotransmitter from nerve terminals
 B Depolarization of  the nerve and  muscle membranes
 C Spontaneous   release   of   calcium   from   the sarcoplasmic reticulum
 D Activation of sodium channels at more negative membrane potentials
Ans. B

Explanation:

Membrane excitability is  related  to  the  ease  with which depolarization opens Na+  channels. The opening of the Na+ channel in response to depolarization is, in part, related to the extracellular Ca2+ concentration; the lower the extracellular Ca2+ concentration, the easier it is for Na + channels to open when the membrane depolarizes. Hyperventilation (lowering arterial CO2  tension) decreases extracellular Ca+ concentration by increasing arterial pH. When pH rises, H+ is released from plasma proteins in exchange for Ca and ionized Ca+ concentration decreases.


Q. 2

In tetany hyperexcitability is due to

 A

Low ca ++ causes T permeability to Na+

 B

Prevent K. release

 C

Prevent Na* & IC- release

 D

I.Ca+‘ produce generation of AP

Q. 2

In tetany hyperexcitability is due to

 A

Low ca ++ causes T permeability to Na+

 B

Prevent K. release

 C

Prevent Na* & IC- release

 D

I.Ca+‘ produce generation of AP

Ans. A

Explanation:

A i.e. Low Ca++ CausesT Na+ permeability

  • A decrease in extra cellular Ca++ Concentration increases the excitability of nerve and muscle cells by decreasing the amount of depolarization necessary to initiate the change in Na+ & IC’ conductance that produce the action potentialQ. In fact Ca++ needs to fall only 50% below the normal before spontaneous discharge occur from peripheral nerves, often causing tetany.
  • The voltage gated calcium channels are slightly permeable to Na+ as well as Ca++;when they are activated both Na+ and Ca++ flow to interior of the fiber. When there is deficit of Ca2+ in ECF, Na+ channels become activated (opened) by very little change of membrane potential (from its very negative resting level to a less negative level). Therefore nerve fibers become highly excitable. Sometime discharging repetitively without provocation rather than remaining in resting stage.
  • Conversely, an increase in ECF Ca++ stabilizes the membrane by decreasing excitability.

Q. 3

The immediate treatment of 10 kg weight infants presented with tetany –

 A

IV Diazepam

 B

IV calcium gluconate with cardiac monitoring

 C

IV slow phenobarbitone

 D

Wait and watch

Q. 3

The immediate treatment of 10 kg weight infants presented with tetany –

 A

IV Diazepam

 B

IV calcium gluconate with cardiac monitoring

 C

IV slow phenobarbitone

 D

Wait and watch

Ans. B

Explanation:

Ans. is ‘b’ i.e., IV calcium gluconate with cardiac monitory

Quiz In Between


Q. 4

A post-Thyroidectomy patient develops signs and symptoms of Tetany. The management is –

 A

i.v Calcium gluconate

 B

Bicarbonate

 C

Calcitonin

 D

Vitamin D

Q. 4

A post-Thyroidectomy patient develops signs and symptoms of Tetany. The management is –

 A

i.v Calcium gluconate

 B

Bicarbonate

 C

Calcitonin

 D

Vitamin D

Ans. A

Explanation:

Ans. is ‘a’ i.e., i.v. calcium gluconate

  • As this patient is having severe symptom of hypocalcemia, he should be promptly treated with I.V. calcium gluconate
  • Now, how will we be able to differentiate between mild and severe symptoms of hypocalcemia. Nowhere I could find specifically differentiated symptom as mild & severe. However, by reading various textbooks, what I consider as mild and severe symptoms is as follows :
  • Mild symptoms of hypocalcemia

numbness or tingling in the perioral area, hands & feet.

– feeling of anxiety

  • Severe symptoms

mental status change

– overt tetany

– muscle cramps

– muscle spasms

– hypotension

prolongation of QT interval on ECG

– severe tetany causing adductor spasm of the vocal cords, laryngospasm

– seizures


Q. 5

Tetany is not seen in:   

March 2005

 A

Malabsorption

 B

Hyperventilation

 C

Antiestrogen therapy

 D

Thyroid Surgery

Q. 5

Tetany is not seen in:   

March 2005

 A

Malabsorption

 B

Hyperventilation

 C

Antiestrogen therapy

 D

Thyroid Surgery

Ans. C

Explanation:

Ans. C: Antiestrogen therapy

Causes of hypocalcemia:

  • Hypoparathryoidism
  • Hyperventilation
  • Vitaminn D deficiency
  • Acute pancreatitis
  • Hypomagnesemia
  • Small bowel resection
  • Secondary hypoparathyroidism, including surgery of the thyroid/parathyroid, trauma, infection, burns, cancer
  • Frequent vomiting
  • Excessive ingestion of alkali
  • Respiratory alkalosis
  • Chronic alcoholism
  • Small bowel bypass
  • Strychnine
  • Hyperaldosteronism
  • Chelation of calcium
  • Low Vitamin D, from causes such as malnutrition, malabsorption, kidney disease, infection and drugs
  • Severe diarrheoa
  • Low calcium diet

Quiz In Between



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