Lesson 1.2.3

1.2.3 page 4

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The Adrenal Cortex

 

cortisol: also called hydrocortisone or cortisone; cortisol is secreted in highest amounts in humans and is produced by the adrenal cortex in response to stimulation by ACTH; involved in enhancing short term stress responses and in stimulating conversion of protein and fat into glucose

 

glucocorticoids: a group of hormones, produced by the adrenal cortex, of which cortisol is of prime importance; influence glucose metabolism from protein and fat, and immune function by suppressing inflammation

 

long term stress responses: responses, mainly stimulated by cortisol, which are of long duration

Cortisol produced by the adrenal cortex is thought to be the most important glucocorticoid in humans. It is primarily concerned with glucose metabolism during periods of long term stress, such as engaging in athletic competition and writing Diploma exams. It also plays a role in helping to maintain high blood pressure. It works in concert with the sympathetic nervous system and the release of epinephrine and norepinephrine by the adrenal medulla. After a time, the stress responses fade and normal conditions are restored in part by the parasympathetic nervous system, as you experienced in the Student Stress! Lab. However, if stress producing stimuli persist, the body may be subjected to an excessively high metabolic rate, high blood pressure, and an elevated heart rate for a prolonged period of time. This is particularly damaging for the circulatory system and is a contributing factor in increasing the risk of heart attacks and atherosclerosis, which you studied in Biology 20.

 

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Cortisol also acts to suppress inflammation, and is sometimes used in the treatment of arthritis and allergies. Side effects, such as reducing the effectiveness of your immune system, limit its usefulness.

 

You can further your understanding of the role that cortisol plays in body homeostasis by reading pages 452 – 453 of your textbook and making notes.  Remember to file your notes in your course folder.

 

Or if you prefer, you may watch the following videos and make some notes for your course folder.

Adrenal Cortex

 

Cortisol is secreted in response to ACTH when the anterior pituitary is stimulated by releasing hormone from the hypothalamus. Secretion is decreased by negative feedback exerted on the anterior pituitary and the hypothalamus as outlined in the general regulatory pathway of tropic hormones in Figure 13.10 on page 441 of your textbook, and in the following video.

 

Adrenocorticotropic Hormone

 

Try This

 

TR 2.

 

Use the following information to answer the next four questions. Where appropriate, practice answering in complete sentences. After checking your answers, file them in your course folder. Consult with your instructor for clarification if you do not understand any questions/answers.

 

Due to tiny tumors growing in Emily’s anterior pituitary, she over-produces ACTH which in turn stimulates over-secretion of cortisol. The cortisol maintains a high metabolic rate by burning protein and fat, constricts her blood vessels, causing an increase in her blood pressure, and causes her heart to race constantly.

  1. Draw a feedback loop that would illustrate this disruption in Emily’s production of cortisol.

  2. Before treatment, Emily’s blood glucose was abnormally high. Explain how this situation could have been the result of overproduction of cortisol.

  3. Emily’s heart rate and blood pressure were elevated around the clock. Explain why this is a potentially life-threatening situation.

  4. Emily was very prone to infections such as colds, laryngitis, and bronchitis. Explain why this was probably the result of elevated cortisol levels.

Check your work.
Self-Check Answers

 

TR 2.

  1. The feedback loop should illustrate the positive feedback in the tropic regulatory pathway for cortisol and aldosterone. It should resemble the one shown below, but could be drawn horizontally rather than vertically like this one. Boxes could be placed around the words hypothalamus, anterior pituitary and adrenal cortex.

  1. Cortisol stimulates the decomposition of proteins, amino acids, and fats, as well as the conversion of their breakdown products into glucose. Too much cortisol would accelerate this process and explain why Emily’s blood had an elevated glucose level.

  1. An increased heart rate and high blood pressure lead to increased risk of heart attack, stroke, aneurysms (bursting of blood vessels), and kidney damage, which are all life threatening situations.

  2. Cortisol decreases the inflammatory response. Inflammation is the immune system’s response to injury and invasion by micro-organisms. It directs the body’s defences to wall off the area, kill the invaders, dispose of dead and/damaged tissue and begin the process of repair. During inflammation the blood supply to the area is increased and the area becomes red and warm. The walls of the blood vessels become leaky and the area swells. White blood cells flock to the area to kill the bacteria/viruses and they release chemicals which continue the inflammation. If the inflammatory response is decreased by elevated levels of cortisol, the invading micro-organisms are not killed and the person becomes sick with, for example, a cold, laryngitis, bronchitis, pneumonia, etc. Also the person may become ill more often if the inflammatory response is dampened.