Monday, May 27, 2013

Endocrine System #2: Stress Regulation

The adrenal gland handles stress through secreting various hormones. The adrenal cortex is responsible for dealing with long-term stress, whereas the adrenal medulla is responsible for dealing with short term stress.

Dealing with Short-Term Stress
  1. Stress causes the release of the acetylcholine, a neurotransmitter
  2. This signals the adrenal cortex to release catecholamines: epinephrine and nor-epinephrine
  3. Effects: 1) increased breakdown of glucagon into glucose;  2) increased blood pressure and bloodflow; 3) increased metabolism; 4) decrease in bloodflow to kidneys and intestines, and more blood flows to the brain, muscles and muscles, and 5) increased breathing rate.

Dealing with Long-Term Stress
  1. Stress causes the hypothalamus to release corticotropin releasing hormone (CRH)
  2. The CRH signals the anterior pituitary gland to secrete adrenalcorticotropic hormone (ACTH)
  3. The adrenal gland synthesizes corticosteroids: glucocorticoid, mineralocorticoid, and sex hormones.
  4. Glucocorticoid (e.g., cortisol) causes the liver to synthesize glucose from various pathways (e.g., fats and proteins). This increases the availability of glucose.
  5. Mineralcoricoid (e.g., aldoesterone) stimulates the reabsorption of salt and water in the kidneys. This increases blood volume, pressure, and flow. 

Stress associated Disorders
Cushing's disease: caused by a pituitary tumor, Cushing's disease results in an excess of glucocorticoid in the patient's body. This causes the patient to have deposits of glucose in their face, abdomen, or neck. It also causes muscle and bone weakness, as well as hyperglycemia. It can be treated by surgery or radiation (to remove the tumour).

Addison's disease: the opposite of Cushing's disease, it is often caused by the patient's immune system attacking the adrenal cortex. The shortage of corticosteroids results in major weight loss, pain in stomach, and dizziness and nausea.