Lab Exam 2
What was the effect of TSH injections on the hypophysectomized rat's BMR? How does the BMR in this case compare with the normal rat's BMR? Was the dose of TSH in the syringe too large, too small, or just right?
TSH injections increased it's BMR, but it was still lower that the normal rat's BMR. The does was too small.
Make a prediction about the basal metabolic rate (BMR) of the remaining rats compared with the BMR of the normal rat
The BMR of both remaining rats will be lower than the normal rat's BMR.
What was the effect of thyroxine injections on the hypophysectomized rat's BMR? How does the BMR in this case compare with the normal rat's BMR
The effect of thyroxine injections on the hypophysectomized rat was an increased BMR. The BMR was below the normal rat's. The dose was too low.
What was the effect of thyroxine injections on the thyroidectomized rat's BMR? How does the BMR in this case compare with the normal rat's BMR?
The effect of thyroxine injections on the thyroidectomized rat was an increased BMR. The BMR was below the normal rat's. The dose was too low
What do you think will happen after you inject TSH into the three rats?
The normal rat will become hyperthyroidic and develop a goiter.
What do you think will happen after you inject thyroxine into the three rats?
The normal rat will become hyperthyroidic but will not develop a goiter.
Propylthiouracil (PTU) is a drug that inhibits the production of thyroxine by blocking the attachment of iodine to tyrosine residues in the follicle cells of the thyroid gland (iodinated tyrosines are linked together to form thyroxine). What do you think will happen after you inject PTU into the three rats?
The normal rat will become hypothyroidic and develop a goiter.
What was the effect of TSH injections on the thyroidectomized rat's BMR? How does the BMR in this case compare with the normal rat's BMR? Why was this effect observed?
There was no effect because there was no thyroid gland.
As a result of the missing hormone(s) in the hypophysectimized rat, what would be some expected symptoms
decreased basal metabolic rate
An injection of TSH to an otherwise normal animal will cause which of the following?
goiter development
An injection of propylthiouracil to an otherwise normal animal will cause which of the following?
goiter development
An injection of thyroxine to an otherwise normal rat will cause which of the following?
hyperthyroidism
Why didn't any of the rats develop a goiter after thyroxine injection?
in all cases, TSH levels were not elevated by the thyroxine injection
What was the effect of thyroid-stimulating hormone (TSH) injections on the normal rat's BMR?
increase in BMR
Thyroxine
most important hormone for maintaining metabolic rate and body temperature
Hypothalamus
primarily secretes tropic hormones that stimulate the secretion of other hormones
Thyroid Stimulating Hormone (TSH)
produced in the pituitary gland
How would you treat a thyroidectomized animal so that it functions like a normal animal
provide the animal T4 supplements
Thyrotropin-releasing hormone (TRH)
secreted by the hypothalamus
Why did the normal rat develop a palpable goiter with the TSH injection?
the TSH receptors on the thyroid gland were excessively stimulated
what was the effect of thyroxine injections on the normal rat's BMR
the effects of thyroxine injections made the normal rat hyperthyroidic
Why did the normal rat develop a palpable goiter with the propylthiouracil injection?
the injection decreased the negative feedback mechanism on TSH
Which of the rats developed a goiter after injection with PTU?
the normal rat
Which of the rats developed a goiter after injection with TSH?
the normal rat and the hypophysectomized rat
Why did the metabolic rates differ between the normal rat and the surgically altered rats?
the normal rat has a higher BMR because it has the glands that stimulate and regulate the release of thyroid hormones
Which rat had the fastest basal metabolic rate (BMR)?
the normal rat injected with thyroxine
if an animal has been hypophysectomized, what effect would you expect to see in the hormone levels in its body
there will be a missing pituitary gland which causes missing TSH
if an animal has been thyroidectomized, what hormone(s) would be missing in its blood
thyroxine
