Please help..with...Exercise 4: Endocrine System Physiology Worksheet

1.   What was the effect of thyroxine on the normal rat’s metabolic rate?  How does it compare to the normal rat’s baseline metabolic rate?  >>Barely increased. The normal rat had a normal secreting of thyroxine by the thyroid gland.
2.   Why was this effect seen? >>Injecting thyroxine into the blood will raise the amount of the hormone, inhibiting the over production of TRH by the hypothalamus.

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Exercise 4 Activity 2 (All):  Determining the Effect of Thyroxine on Metabolic Rate

1.   What was the effect of thyroxine on the normal rat’s metabolic rate?  It caused the rate to increase. How does it compare to the normal rat’s baseline metabolic rate?  The injected rat’s metabolic rate was much higher than the baseline rat.
2.   Why was this effect seen?  Because it already has thyroxin and when you add more of it then it goes even quicker.
3.   What was the effect of thyroxine on the thyroidectomized rat’s metabolic rate?  Thyroxine caused the rate to increase How does it compare to the thyroidectomized rat’s baseline metabolic rate?  The injected rat’s metabolic rate was slightly higher than the baseline rat. Metabolic rate was raised to try to reach normal rates even though the rate was still lower than the baseline.
4.   Why was this effect seen?   It has its pituitary gland saw some hormones are there.
5.   What was the effect of thyroxine on the hypophysectomized rat’s metabolic rate?  Thyroxine caused the rate to increase. How does it compare to the hypophysectomized rat’s baseline metabolic rate?  The injected rat’s metabolic rate was much higher than the baseline rat.
6.   Why was this effect seen? The injected thyroxine compensated for the thyroxine lost when the pituitary gland was removed. The pituitary gland did not produce TSH, therefore the thyroid gland did not produce thyroxine.

Thanks KK