PhysioEx Exercise 4 Activity 1
Metabolism
-broad range of biochemical reactions occuring in the body -includes catabolism and anabolism
Thyroid Stimulating Hormone (TSH)
-controlled by pituitary gland -causes thyroid gland cells to secrete T3 and T4; stimulates thyroid growth -target tissue: thyroid gland
What is a goiter?
A goiter is an abnormal enlargement of the thyroid gland from too much TSH being released.
The steps you described above are part of a negative feedback system.A) Explain what this means (i.e. what is a negative feedback system?).
A negative feedback system reverses a change in a controlled condition to maintain the body's equilibrium/homeostasis.
What does it mean if a hormone is a tropic hormone?
A tropic hormone stimulates an endocrine gland to secrete a hormone.
In your own words, describe the effect of injected propylthiouracil on the metabolic rate of each of the 3 rats. A) Normal rat B) Thyroidectomized rat C) Hypophysectomized
A) Normal rat - PTU caused a decrease in the BMR since it inhibits thyroxine production. The rat became hypothyroidic and a goiter was present. B) Thyroidectomized rat - No change since there was no thyroid C) Hypophysectomized rat - Because the pituitary gland was removed, TSH was not able to be produced. Changes in metabolism occurred because the negative feedback mechanism could not be followed through due to the missing organs unable to secrete hormones.
Which treatment(s) caused a goiter in each of the following rats? A) Normal rat B) Thyroidectomized - *Explain WHY there was or was not a goiter present in this rat. C) Hypophysectomized
A) Normal rat - TSH & PTU B) Thyroidectomized - There was no thyroid gland present, so TSH is not able to stimulate the thyroid for the production of thyroxine, so a goiter was not present. C) Hypophysectomized - TSH
In this activity you used a thyroidectomized rat and a hypophysectomized rat. Describe what each of these conditions mean. A) Thyroidectomized B) Hypophysectomized
A) Thyroidectomized - the thyroid gland was surgically removed B) Hypophysectomized - the pituitary gland was surgically removed
f an animal has been hypophysectomized, what effect would you expect to observe in the hormone levels in its body?
Because the pituitary gland was removed, TSH levels would be extremely low or nonexistent and this would trigger a decrease in BMR.
In your own words, describe the effect of injected TSH on the metabolic rate of each of the 3 rats. A) Normal rat B) Thyroidectomized rat C) Hypophysectomized rat -
Due to the increase of TSH, the amount of thyroxine increased which resulted in an increased BMR. The rat became hyperthyroidic. B) Thyroidectomized rat - Since the thyroid was surgically removed, the TSH injections did not affect the thyroidectomized rat's BMR because the thyroid gland was unable to be stimulated. The BMR remained consistent with the 1st trial where there was no injection C) Hypophysectomized rat - hyperthyroidism developed and a goiter was present.
How does thyrotropin releasing hormone (TRH) travel from the hypothalamus to the pituitary gland?
Hypothalamic-pituitary portal system.
Describe the role of the hypothalamus in the production of thyroxine.
Hypothalamus stimulates the anterior pituitary to produce TSH, which stimulates the Thyroid gland to produce thyroxine.
What is the role of the hypothalamus in the production of thyroid stimulating hormone (TSH)?
Hypothalamus stimulates the anterior pituitary to produce TSH.
How could you treat a thyroidectomized rat so that it functions like a " normal" rat? How would you verify that your treatments were safe and effective?
Inject it with thyroxine
Propylthiouracil inhibits the production of thyroxine by blocking the attachment of iodine tot he amino acid tyrosine. What naturally occurring problem in some parts of the world does this drug mimic?
Iodine Deficiency
Using a water-filled manometer, you observed the amount of oxygen consumed by rats in a sealed chamber. What happened to the carbon dioxide the rat produced while in the sealed chamber?
It was absorbed by soda lime rocks
What is propylthiouracil (PTU)?
It's 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
Why didn't the administration of propylthiouracil have any effect on the metabolic rate of either the thyroidectomized rat or the hypophysectomized rat?
PTU inhibits the production of thyroxine. These rats do not have a pituitary or thyroid gland, so they do not produce thyroxine. PTU would have no effect.
What was the effect of propylthiouracil (PTU) injections on the normal rat's BMR? Why did this rat develop a palpable goiter?
PTU injections caused the normal BMR (1704 mL O2/kg/hr) to decrease to a hypothyroidic rate of 1488mL O2/kg/hr. Since PTU inhibits thyroxine, the rat developed a palpable goiter.
. You were asked to "palpate the thyroid" of each rat after. What does this mean (i.e. what would you have done to a live rat in a real experiment?)? A) WHY did you do this? (i.e. what were you looking for?)
Palpating the thyroid means touching the neck of the individual being examined with varying pressure to determine the growth of the thyroid. The researcher would have had to "pinch" the rat's neck or use one finger to trace down its neck to feel the thyroid gland. A) You could be looking for a goiter or anything usual such as texture, tenderness, growth, or lumps.
How would you treat a thyroidectomized animal so that it functions like a "normal" animal?
Provide the animal T supplements.
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?
Since the thyroid was surgically removed, the TSH injections did not affect the thyroidectomized rat'sBMR because the thyroid gland was unable to be stimulated. The BMR remained consistent with the1st trial where there was no injection (1549.18 mL O2/kg/hr).
In your own words, describe the effect of injected thyroxine on the metabolic rate of each of the 3 rats. A) Normal rat B) Thyroidectomized rat C) Hypophysectomized rat
Since there was an increase in thyroxine levels, the rat developed hyperthyroidism. This causes the BMR to increase and a goiter developed. B) Thyroidectomized rat - The oxygen levels increased, which caused the BMR to increase as well, but a goiter was not found. C) Hypophysectomized rat - The oxygen levels increased, which caused the BMR to increase as well, but a goiter was not found.
Name the hormone released by the thyroid gland involved in metabolism.
T4
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? Was the dose of thyroxine in the syringe too large, toosmall, or just right?
The BMR of the hypophysectomized rat dramatically changed as well. Initially, the rat was hypothyroidic (1573.77 mL O2/kg/hr), and it became hyperthyroidic (1942.62 mL O2/kg/hr) after the thyroxine injection. Therefore, thyroxine caused an increase in the rat's BMR. The normal rat's BMR(2040 mL O2/kg/hr) was greater than that of the hypophysectomized rat's BMR (1942.62 mL O2/kg/hr).So, the dose of thyroxine was too small. A goiter did not develop.
this case compare with the normal rat's BMR? Was the dose of thyroxine in the syringe too large, too small, or just right?
The BMR of the thyroidectomized rat drastically changed. Initially, the rat was hypothyroidic (1549.18mL O2/kg/hr), and it became hyperthyroidic after the injection (1918.03 mL O2/kg/hr). Therefore,thyroxine caused an increase in the rat's BMR. The normal rat's BMR (2040 mL O2/kg/hr) was greater than that of the thyroidectomized rat (1918.03 mL O2/kg/hr). So, the dose of thyroxine was too small. A goiter did not develop.
Explain HOW you determined basal metabolic rate (BMR).
The BMR was calculated by taking the ml of O2 consumed and multiplying it by 60 to convert minutes to hours. The unit of measurement would now be O2/ hr. This value was then divided by the rat's weight in kg to calculate the BMR, which is measured in O2/kg/hr
case compare with the normal rat's BMR? Was the dose of TSH in the syringe too large, too small, or just right?
The TSH injections increased the hypophysectomized rat's BMR. Initially, the rat was hypothyroidic(1573.77 mL O2/kg/hr) and after the injection, it became hyperthyroidic (1942.62 mL O2/kg/hr).However, the normal rat had a higher BMR (2040 mL O2/kg/hr), so the dodge was too small.
Why did the normal rat develop a palpable goiter with the TSH injection?
The TSH receptors on the thyroid gland were excessively stimulated.
12What was the effect of PTU injections on the hypophysectomized rat's BMR? How does the BMR, in this case, compare with the normal rat's BMR? Why was this effect observed?
The effects of PTU injections could not be observed because the hypophysectomized rat's pituitary gland was removed. The hypophysectomized rat's BMR (1549.18 mL O2/kg/hr) was higher than that of the normal rat's BMR (1488 mL O2/kg/hr). The BMR of the hypophysectomized rat did not change from the initial trial with no injection.
What was the effect of PTU 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?
The effects of PTU injections could not be observed because the thyroidectomized rat's thyroid gland was surgically removed. The thyroidectomized rat's BMR (1549.18 mL O2/kg/hr) was higher than that of the normal rat's BMR (1488 mL O2/kg/hr). The BMR of the thyroidectomized rat did not change from the initial trial with no injection.
Which of the following statements is true?
The hypothalamus primarily secretes tropic hormones that stimulate the secretion of other hormones.
Describe the steps involved in the release of thyroxine (beginning with the hypothalamus).
The hypothalamus stimulates the anterior pituitary gland by releasing TRH. The anterior pituitary gland releases TSH, which stimulates the thyroid and results in the release of thyroxine.
Why did the normal rat develop a palpable goiter with the propylthiouracil injection?
The injection decreased the negative feedback mechanism on TSH.
Why did the metabolic rates differ between the normal rat and the surgically altered rats? How well did the results compare with your prediction?
The metabolic rates differentiated between the normal rat and the surgically altered rats as a result of the surgical removal of endocrine glands (the thyroid and pituitary gland). Hormones that were specifically stimulated and secreted by these glands, thyroid hormones and TSH, were unable to besynthesized and/or secreted.
Which rat had the fastest basal metabolic rate (BMR)?
The normal rat, when injected with thyroxine, had the fastest BMR.
what would happen to the fluid levels of the manometer (and, thus, the results of the metabolism experiment) if the rats in the sealed chamber were engaged in physical activity (such as running in a wheel)?
The rats metabolism would be increased, so they would use more oxygen.
What was the effect of thyroxine injections on the normal rat's BMR?
There was an increase in thyroxine levels, so the rat developed hyperthyroidism. There was an increase in BMR from 1704 O2/kg/hr to 2040 O2/kg/hr. A goiter did not develop.
Why didn't the administration of TSH have any effect on the metabolic rate of the thyroidectomized rat?
This rat has no thyroid to be stimulated. The thyroid has been removed
If an animal has been thyroidectomized, what hormone(s) would be missing in its blood?
Thyroxine would be missing from the blood since it is secreted by the thyroid gland.
What was the effect of thyroid-stimulating hormone (TSH) injections on the normal rat's BMR?
When TSH was injected, the rat's BMR increased from 1704 mL O2/kg/hr initially to 1920 mL O2/kg/hr afterward. This increase resulted in the rat becoming hyperthyroidic and developing a goiter.
What happens when thyroxine levels are high?
When thyroxine levels are high, the hypothalamus is inhibited from producing TRH and notifies the anterior pituitary gland to inhibit the production of TSH.
What happens when thyroxine levels are low?
When thyroxine levels are low, the hypothalamus secretes more TRH to stimulate the anterior pituitary gland to secrete more TSH. TSH stimulates the secretion of thyroxine from the thyroid gland.
What can cause a goiter?
When too much TSH is released, a goiter develops.
Which of the following statements about metabolism is false?
You correctly answered: All of the energy from metabolism is ultimately stored in the chemical bonds of ATP.
Catabolism
breakdown of more complex substances into simpler ones with release of energy
Anabolism
building up of small molecules into larger, more complex ones via enzymatic reactions
hypothalamic pituitary portal system
contains a single port vein that connects 2 capillary beds. primarily secretes tropic hormones
As a result of the missing hormone(s) in the hypophysectomized rat, what would be an expected symptom?
decreased basal metabolic rate.
Thyrotropin-releasing hormone (TRH)
directly linked to thyroxine and TSH production
An injection of TSH to an otherwise normal animal will cause which of the following?
goiter development
n injection of propylthiouracil to an otherwise normal animal will cause which of the following?
goiter development.
Define metabolism in your own words.
he process of all chemical reactions (catabolic and anabolic) within the body to maintain life.
An injection of thyroxine to an otherwise normal rat will cause which of the following?
hyperthyroidism.
when circulation levels of thyroxine are low
hypothalamus secretes more TSH, which further stimulates the secretion of thyroxine from the thyroid gland
. What specifically did you measure (in order to determine basal metabolic rate) when you placed each rat into the chamber?
ml of O2 consumed was measured when the rat was placed in the chamber.
thyroxine
most important hormone for maintaining metabolism and body heat
Why didn't any of the rats develop a goiter after thyroxine injection?
n all cases, TSH levels were not elevated by the thyroxine injection.
hypothalamus
primary endocrine gland vital participant in thyroxine and tsh production
Thyroid-stimulating hormone (TSH) is
produced in the pituitary gland.
Thyrotropin-releasing hormone (TRH) is
secreted by the hypothalamus.
Thyroxine is
the most important hormone for maintaining the metabolic rate and body temperature.
