IGCSE Biology Paper-3: Specimen Questions with Answers 272 - 272 of 358

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The boxes on the left contain the names of parts of the body that produce hormones.

The boxes in the center contain the names of hormones.

The boxes on the right contain functions of these hormones.

Rate of Breathing

Question 272 (1 of 4 Based on Passage)


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Where does thyroid gland located in our body and what is the function of it?


Thyroid Gland

  • It is single and bilobed gland present on either side of trachea below larynx the 2-lobes remain connected by a non-glandular tissue called Isthmus.
  • It is endodermal in origin
  • It is the largest endocrine gland in the body (weighing ~35 gm) .

Calcitonin (Or Thyrocalcitonin)

  • It is proteinaceous and non-iodinized hormone (Iodine absent) .
  • It is secreted from C (clear) – cells or Parafollicular cells (outside thyroid follicles)
  • It is hypocalcimic factor and decreases the amount of Ca2 + in the blood.
  • It is angonistic to PTH (Para-thyroid hormone) .

Thyroxine (T4)

  • It is Tetra-ido-thyronine and is secreted from the cells of thyroid follicles. T4 with T3 are stored as a colloidal material in the follicles.
  • Thyroxine regulates basic metabolic rate (BMR) - stimulating heartbeat, breathing rate etc.
  • It causes demineralization of bones in adults (by stimulating osteoclasts - the bone eating cells) .
  • It causes hyperglycemia by stimulating glycogenolysis and Gluconeogenesis.
  • It causes nervous excitation also.
Stimulating Heartbeat

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