Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 7 Stress and Adaptation

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Homeostasis The body requires that a level of homeostasis, or constancy, be maintained during changes in internal and external environments Give an example in which your body kept some aspect of its internal environment stable. Aspects you might consider include: –Water balance –Weight –Blood glucose –Temperature

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Allostasis A difference between the perceived situation and desired situation causes the person to take action Cognitive activation theory of stress

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins General Adaptation Syndrome Also called generalized stress response –Corticotropin-releasing hormone (CRH) production –Antidiuretic hormone release –Sympathetic nervous system (SNS) activation –Renin-angiotensin-aldosterone pathway activation

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins stressors change the internal environment of part of the body general adaptation response helps maintain normal function in spite of the stressor signs and symptoms of the change signs and symptoms of the general adaptation response

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Cortisol— The “Stress Hormone” Helps regulate the stress response Diverts metabolism from building tissues to supplying energy for dealing with the stress Causes signs and symptoms of chronic stress CRH ACTH Hypothalamus Anterior pituitary Adrenal cortex Cortisol Alters glucose, fat, and protein metabolism Suppresses inflammatory and immune responses

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Cortisol Release Increases blood glucose Stronger sympathetic system effect on heart rate Decreases nonessential energy-using activities like: –Hormone production ºMetabolic rate and reproductive functions decrease –Bone formation –Red and white blood cell production ºImmune system becomes depressed

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Why does cortisol production result in increased blood glucose levels? a.Glucose leads to a strong sympathetic nervous system response. b.Glucose stimulates RBC production. c.Glucose stimulates release of adrenaline. d.Glucose provides energy.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer d.Glucose provides energy. Rationale: The body’s energy requirements increase during periods of stress. Cortisol is the “stress hormone” — one of the effects of cortisol release is increased blood glucose levels. Glucose helps to meet the body’s increased demand for energy.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Antidiuretic Hormone (ADH) Also called vasopressin Causes vasoconstriction Makes kidneys reabsorb water from urine to blood

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sympathetic System— “Fight-or-Flight” Response Rapid response to trauma and emergency Epinephrine (adrenalin) and norepinephrine (noradrenalin) both released Both attach to adrenergic receptors on cells hypothalamus SNS neurons adrenal medulla Pain, fear, low BP SNS activated Norepinephrine Epinephrine released into blood

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sympathetic System— “Fight-or-Flight” Response (cont.) Blood pressure restored Blood flow to skin, guts, and kidneys reduced Skin becomes pale Urine production decreases GI activity decreases epinephrine and norepinephrine heart increased HR increased heart strength increased BP blood vessels vasoconstriction in skin, guts, kidneys

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Renin-Angiotensin-Aldosterone Pathway Activated by: –Sympathetic system –Decreased blood flow to kidneys Angiotensin I: weak vasoconstriction Angiotensin-converting enzyme (ACE) Angiotensin II: stronger vasoconstriction ACE Kidneys release renin Angiotensin I Angiotensin II

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Renin-Angiotensin-Aldosterone Pathway (cont.) Angiotensin II: stronger vasoconstriction Also stimulates the adrenal cortex Aldosterone released adrenal cortex Angiotensin II Aldosterone

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Tell whether the following statement is true or false. Angiotensin-converting enzyme must be present in order for aldosterone to be released by the adrenal gland.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer True Rationale: Without angiotensin-converting enzyme, angiotensin II would not be created. Angiotensin II stimulates the adrenal cortex to produce aldosterone.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Renin-Angiotensin- Aldosterone Pathway (cont.) Aldosterone released Na + /K + ATPase in nephrons activated –Kidneys reabsorb Na + and water –Kidneys secrete K + kidneys aldosterone reabsorb Na + and water increased blood volume oliguria secrete K +

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins stressors change the internal environment of part of the body general adaptation response helps maintain normal function in spite of the stressor signs and symptoms of the change signs and symptoms of the general adaptation response

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Scenario: After an accident, a patient has the following: Increased heart rate No urine production No bowel sounds Pale, sweaty skin Low blood pressure Dilated pupils Elevated blood glucose Question: What should be fixed first? Why?

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins releases which affect release which affect central nervous system hormones and neurotransmitters immune cells inflammatory mediators

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Effects of Stress on the Immune System Decreased immune cell production Decreased thymus activity Changes in the kind of immune cells produced

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question How does stress affect your immune system? a.The thymus atrophies. b.Fewer lymphocytes are produced. c.Inflammatory mediators are released. d.All of the above

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer d.All of the above Rationale: Stress causes the immune system to be suppressed. The thymus gland atrophies (shrinks), so that fewer T lymphocytes are produced. Monocytes and lymphocytes cross the blood-brain barrier and release inflammatory mediators and cytokines.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Physiologic Stress Stress-induced changes in body functions Detected by body’s normal regulatory sensors The body alters function to restore normal balance When normal balance is restored, negative feedback stops the reaction

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Psychosocial Stress Directly affects the central nervous system Turns on the stress responses, even when the body’s internal sensors have not detected an imbalance Questions: Do the stress responses solve the person’s problem? Will negative feedback tell them when to turn off?

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Acute Stress Question: Which organs of the body would you expect to see damaged by acute stress? Why?

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Results of Long-term Stress Chronic stress –Sympathetic activity and cortisol are elevated –Complications result from the reduced immune response Post-traumatic stress disorder –Sympathetic system is activated –Cortisol levels are decreased

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Scenario Mr. P saw violent combat in the army, but he dealt with it and has become a successful air traffic controller. He is 50 and overweight: –With increased blood pressure and occasional tachycardia –Insomnia –GI discomfort –He has had several colds already this year, and wants a flu shot Question: What about his case might be stress-related?

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Scenario (cont.) The doctor has recommended relaxation therapy Mr. P is furious about this “new-age gobbledygook” Question: How will you explain its physiologic basis to him?