I am interested in how the adrenal glands control stress.
The cortex is responsible for secreting 3 main classes of chemicals:
1) the glucocorticoids (represented by cortisone (cortisol);
2) the mineralocorticoids (represented by aldosterone);
and 3) sex steroids (represented by androstenedione).
The glucocorticoids exert two main actions: a)antiinflammatory and b) gluconeogenesis. Gluconeogenesis is a process leading to the formation of new glucose from either amino acids or glycerol (from triglycerides). The glucocorticoids are released when glucose levels are low or when there is a need for antiinflammatory action.
The mineralocorticoids (primarily aldosterone) exert two main actions: a) proinflammatory and b) moving sodium from kidneys to blood - with excretion into urine of either potassium or hydronium ion. Aldosterone is released when there is a need for inflammation or low blood levels of sodium.
The sex steroids represented by androstenedione are active prior to puberty and after menopause in females and prior to puberty and after 50+ years in the male. During the life cycle they are anabolic; that is, they cause a build up of proteins in the body.
The medulla of the adrenal glands is responsible for producing adrenaline or epinephrine. Think of this chemical as a booster for the sympathetic nervous system. It is primarily responsible for increasing blood pressure, increasing heart rate, glycogenolysis (breakdown of glycogen into glucose), increasing sweating - hands and feet, dilating pupil and adjusting lens for far vision. It is very important to recognize that adrenaline or epinephrine has no influence on skeletal muscle movements. While many call epinephrine the "fight or flight chemical" it does not allow us to either fight or flight.
The cerebral cortex of the brain (along with the basal ganglia and cerebellum) control skeletal muscle movements.
Functionally you should think of two regions in the cerebrum (cerebral cortex) that are influencial in our personalities and responses to stress. One is referred to as the primitive cortex.
The primitive cortex is our "instinct" area.
The second functional area is the neocortex (new brain or society brain). It is here that "rules of behavior" exist. The so-called right or wrong based on family or society rules. Obviously our responses to stress are based on our experiences.
It is also important to point out at this time that the production of the glucocorticoids, mineralocorticoids and sex steroids is dependent on a supply of cholesterol to the adrenal cortex. The cholesterol needed to synthesize these chemicals is brought to the adrenal cortex by the lipoprotein called LDL (low density lipoprotein) - often referred to as "bad cholesterol".
Dr. Bill asks you to consider that the only way cholesterol can be brought to the adrenal glands is via LDL. The other carrier for cholesterol called HDL (High density lipoprotein- so called "good cholesterol" is responsible for transporting cholesterol back to the liver.
Cholesterol is the precursor for all steroid hormones - glucocorticoids, mineralocorticoids, androstenedione, estrogen, progesterone, and testosterone.
Use the following example to see how adrenal cortex steroids work.
A person is put on a diuretic - a drug to cause excretion of salt and water into urine.
When the levels of salt - sodium chloride are reduced too much - the adrenal cortex is stimulated to release the mineralocorticoid - aldosterone.
Aldosterone causes movement of sodium from the kidneys to the blood stream. At the same time it causes the excretion of potassium from the blood into the urine.
Hence the reason people on diuretics are urged to eat more potassium rich foods.
Because the aldosterone can also exert proinflammatory action - the adrenal glands are forced to release the glucocorticoid - cortisone which exerts anti-inflammatory action BUT also stimulates gluconeogenesis - the formation of new glucose from either amino acids ( from proteins) or glycerol (from triglycerides).
The release of cortisone with the increase in blood sugar increases the need for the pancreas to release insulin.
Long-term use of or excessive use of major diuretics can lead to DIABETES.
In addition, in those carbohydrate-lipid linked people, cortisone breaks down triglycerides into glycerol (used to make glucose) and three fatty acids.
Fatty acids are not converted into glucose but can be used for energy.
From this example, one should note that whenever aldosterone is released it causes an increase in salt appetite; and cortisone causes an increase in our sugar appetite.
