Question

A 21-year-old male visits with his family doctor at the urging of his parents when home for Spring Break. The parents are concerned because their son has lost a significant amount of weight. The young man is concerned because he is experiencing a heart rate of 120bpm while at rest and much higher when exercising. Additionally, his blood pressure averages 137/82 based upon four recordings. He has a recurring headache, tremors in his hands and suffers dyspnea.

This individual has been generally health for his entire life, eats a reasonably good diet and is very active, thus the above symptoms are concerning. Standard blood tests show normal levels of blood cells, however there is an elevated amount of metadrenalines (metabolite by-product of adrenaline) and the urinalysis also shows an elevated amount of metabolites of catecholamines. The physician then orders a 24-hour urine test where the patient collects urine at regular intervals for a 24-hour period. The patient is warned to avoid stimulants such as cocoa and caffeine during this time period. The results of this test confirm elevated metabolites of catecholamines. The physician suspects a condition called pheochromocytoma, which is a (usually) non-cancerous tumor of the adrenal gland. This tumor causes the excess secretion of catecholamines. To confirm this suspicion, the physician orders a specialized type of CT scan, called MBIG. This type of scan utilizes radioactive iodine as a contrast agent for visualization of masses as described above. A sample of MIBG results is shown below:

The MIBG confirms the presence of a tumor on the adrenal gland and the young man is scheduled for surgery to remove the mass. It is non-cancerous and he resumes his life. As a side note, current estimates are that only about 10% of adrenal tumors are cancerous.

2. Which division of the autonomic nervous system are catecholamines synergistic with? If they were produced by the nervous system as neurotransmitters, how would they interact with the body differently than they do as hormones? In your comparison, make sure to include: how the chemical signals travel to their target cells, how quickly the signaling occurs, how long the signaling is sustained, and whether the signaling occurs locally or systemically (throughout the body). (3 pts)

Answer 1

It is the sympathetic autonomous system which is synergistic with the catecholamines . This is because the adrenal medulla is innervated by sympathetic preganglionic fibres.

If catecholamines were neurotransmitter , they will have sympathetic effects on the body , such as -

• Increasing the heart rate
• Increasing the blood pressure
• Increased muscle readiness.

If it is a neurotransmitter it will transfer through nerves . But if it is a hormone , it will travel through blood .

The signalling is sustained more if it works as a hormone .