Endocrine System Physiology

Lab 28B: Endocrine System Physiology

Computer Simulation

Introduction

The endocrine system is the second greatest control system of the body and has many effects on the tissues and organs. The thyroid gland, which is a part of the endocrine system, releases a hormone that maintains metabolism. This hormone is thyroxine. Thyroxine production is controlled by thyroid stimulating hormone, which is released by the pituitary gland. TSH stimulates the thyroid gland to produce thyroxine. In this experiment, the effects of TSH and thyoxine on metabolic rate are investigated.

Estrogen is a hormone produced by the ovaries that helps the uterus to develop. The removal of the ovaries eliminates the source of estrogen and the uterus cannot develop properly. In one of the following experiments, the effect of hormone replacement therapy is investigated.

Insulin regulates blood glucose levels and is produced by the pancreas. When the pancreas does not produce insulin, the cells cannot absorb glucose from the blood. This results in diabetes mellitus type I. In one of the following experiments, the effects of insulin treatment are investigated for type I diabetes.

Hypothesis

Experiment 1: Determining Baseline Metabolic Rates

I hypothesize that the metabolic rate will be greater for the normal rate, then the thyroidectomized rat. The hypox rate will have the lowest metabolic rate.

Experiment 2: Determining the Effect of Thyroxine on Metabolic Rate

I hypothesize that metabolic rate will increase with the injection of thyroxine.

Experiment 3: Determining the Effect of TSH on Metabolic Rate

I hypothesize that the injection of TSH will increase the metabolic rate of the all the rats except for the thyroidectomized rat.

Experiment 5: Hormone Replacement Therapy

I hypothesize that the rat receiving estrogen injections will have heavier more developed uterine tissue.

Experiment 7: Comparing Glucose Levels Before and After Insulin Injection

I hypothesize that glucose levels of the diabetic rat will be closer to the glucose levels of the normal rat after the insulin injection.

Materials and Methods

The materials used for this lab were the PhysioEx 6.0, the Human Anatomy & Physiology Lab Manual and the computer.

Experiment 1: Determining Baseline Metabolic Rates

A normal rat was placed in the chamber and weighed. The clamp was then closed and the timer set to 1 minute. After 1 minute the manometer and syringe were connected and the clamp was opened. Air was injected into the tube until the fluid in each arm of the U-tube was level. The amount of O2 used in an hour was calculated and the metabolic rate for the normal rate was obtained. This process was repeated for the thyroidextomized rat and the hypopysectomized rat.

Experiment 2: Determining the Effect of Thyroxine on Metabolic Rate

A normal rat was injected with thyroxine and placed in the chamber and weighed. The clamp was then closed and the timer set to 1 minute. After 1 minute the manometer and syringe were connected and the clamp was opened. Air was injected into the tube until the fluid in each arm of the U-tube was level. The amount of O2 used in an hour was calculated and the metabolic rate for the normal rate was obtained. This process was repeated for the thyroidextomized rat and the hypopysectomized rat.

Experiment 3: Determining the Effect of TSH on Metabolic Rate

A normal rat was injected with TSH and placed in the chamber and weighed. The clamp was then closed and the timer set to 1 minute. After 1 minute the manometer and syringe were connected and the clamp was opened. Air was injected into the tube until the fluid in each arm of the U-tube was level. The amount of O2 used in an hour was calculated and the metabolic rate for the normal rate was obtained. This process was repeated for the thyroidextomized rat and the hypopysectomized rat.

Experiment 5: Hormone Replacement Therapy

A control rat was given 7 injections of saline over 7 days and an experimental rat was given 7 injections of estrogen over 7 days. The uteruses from each rat were removed and weighed.

Experiment 7: Comparing Glucose Levels Before and After Insulin Injection

A control rat was given a saline injection and an experimental rat was given an alloxan injection. Both rats were given an insulin injection. Blood was drawn from both rats and the glucose levels were compared.

Results

Experiment 1: Determining Baseline Metabolic Rates

The baseline metabolic rate for the normal rat was 1682.7 ml O2/kg/hr, the rate for the thyroidectomized rat was 1473.6 ml O2/kg/hr, and the rate for the hypox rat was 1473.0 ml O2/kg/hr.

Baseline Normal Rat Thyroidextomized Rat Hypophysectomized Rat

Weight 249.6 244.3 244.4

ml O2 in 1min. 7.0 6.0 6.0

ml O2 in 1 hour 420.0 360.0 360.0

Metabolic Rate 1682.7 1473.6 1473.0

Experiment 2: Determining the Effect of Thyroxine on Metabolic Rate

The metabolic rate was calculated after the rats had been injected with thyroxine. The metabolic rate for the normal rat was 1802.9 ml O2/kg/hr, the rate for the thyroidectomized rat was