a HAPS Objectives

-identity, secretory control, & functional roles of the major hormones of the pituitary, adrenal medulla and adrenal cortex, thyroid, parathyroid, pancreas, gonads, & pineal, including the effects of hypo- and hyper- secretion
-hormonal response to stress

The endocrine system helps regulate many activities of organ systems. Details are given where appropriate in A & P I & II.  So the significance of most hormones introduced here becomes clear when the relevant organ system/s is/are studied.  Here, we first build upon our earlier work on the autonomic nervous system, and second study thyroid hormone, as most people know that it is involved in the regulation of their metabolism.

The Effects of  Epinephrine and Norepinephrine

We have just seen the effects on Mr. Norm's cardiovascular system of hypo- and hyper- activity of his sympathetic nervous system (SNS).  Now we investigate some effects of epinephrine and norepinephrine, the hormones whose secretion is controlled by the SNS.  The adrenal medulla secretes 80% epinephrine (E) and 20% norepinephrine (NE).  We will investigate the effects of increasing and decreasing in turn the plasma levels of each hormone.  Remember that Mr. Norm will try to compensate for the deviations from normal caused by our manipulations.

Start QCP.  Make sure that all items under View are checked.  E and NE are listed under the Synapse logo as Circulating Catecholamines.  Their normal plasma levels are given.  Note that E is a beta agonist, while NE is an alpha agonist. Write in the normal values of all the variables listed in the table below, you have previously encountered the location of all items. It's your choice for the last item  Look for something interesting as you work.  To lower the hormone plasma levels, one at a time, maximize their Clearance (means out of the plasma into the urine).  To raise plasma levels switch on the Pump, and make the Rate at least equal to their adrenal secretion rate. After each change Go compute for 1 hour and complete a column. Restart before making the next change.
 

Item and normal value	Exp. 1 (low E)	Exp. 2 (high E)	Exp. 3 (low NE)	Exp. 4 (high NE)
Circulating E
Circulating NE
BP (syst/diast)
Pulse
Cardiac Output
Total Peripheral Resistance
SNS activity
Vagus activity
Your choice

What do your results show about the actions of E and NE?

Are the actions of E and NE the same, explain?

Why are SNS activity and Vagus activity included in the table?

Was Mr. Norm compensating during your experiments, explain?
 

The Effects of  Hypo- and Hyper- Thyroidism on Mr. Norm's Metabolic Rate

This experiment is not  in the beta copy we have of QCP3, it can be done with QCP2 or HUMAN.  The experiment is often done in the laboratory on a mouse or rat as it is easy to lower thyroid hormone secretion using certain drugs; and to increase activity thyroid hormone can be injected or given orally.  Both treatments are available to humans with thyroid problems.  But it is even easier to do these experiments on Mr. Norm!  (Re) start QCP.  Add all items under View.  Complete the normal column in the table:
 

Normal

500 ng/min THY for 24 hr

0 ng/min THY for 24 hr

BP syst/diast_______________________________________________________________________

Cardiac Output_____________________________________________________________________

Pulse______________________________________________________________________________

Ventilation__________________________________________________________________________

Body Temperature____________________________________________________________________

Oxygen Uptake______________________________________________________________________

Now change THY to 500 ng/min (5x normal). Go compute for a day. The effects of changing the thyroid's rate of secretion take a few hours to develop. Enter the 24 hr values. Look at QCP's charts, is there evidence other than what is in the table above, that the high level of hormone secretion is affecting Mr. Norm?  Restart and block thyroid secretion.  Enter your results in the table and check the charts.

Last, relate the changes from normal in these variables to the effects given in textbooks, of hyper- and hypo- secretion.  Are the effects on the cardiovascular variables what you expect? Are the effects on body temperature, metabolic rate and breathing what you expect?  Is QCP an adequate model for thyroid hormone actions, and hyper- and hypo- secretion? What areas of thyroid action are missing from QCP?