CHAPTER 9STRESS AND ADAPTATION

Essentials of Pathophysiology

PRE LECTURE QUIZ (TRUE/FALSE)

The sympathetic nervous system manifestation of the stress reaction has been called the fight-or-flight response.

According to Walter B. Cannon, allostasis is achieved through a system of carefully coordinated physiologic processes that oppose change, not the ability to achieve stability through change.

The alarm stage is the third stage of the general adaptation syndrome (GAS).

The stress response is strongly influenced by both the nervous and the endocrine systems.

Nutrition, physiologic reserve, psychosocial factors, and sleep–wake cycles are known to affect a person’s appraisal of a stressor and the coping mechanisms used to adapt to the new situation.

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PRE LECTURE QUIZHardine

ss

Hormones

Intrusion

Physiologic

Stressors

•With regard to post-traumatic stress disorder (PTSD), the ______________ state refers to the reexperiencing of an event through the occurrence of “flashbacks” during waking hours or nightmares in which the past traumatic event is relived.

•According to Hans Selye, the events or environmental agents responsible for initiating the stress response are called _________________.

•There are a number of ________________ that are released from the hypothalamus, anterior pituitary, and adrenal cortex in response to stress.

•__________________ describes a personality characteristic that includes having a purpose in life and the ability to conceptualize stressors as a challenge, rather than a threat.

•The ability of body systems to increase their function given the need to adapt is known as _________________ reserve.

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

ALLOSTASIS A difference between the perceived situation

and desired situation causes the person to take action

Cognitive activation theory of stress

GENERAL ADAPTATION SYNDROME (GAS)

Also called generalized stress response Corticotropin-releasing hormone (CRH)

production Antidiuretic hormone release Sympathetic nervous system (SNS)

activation Renin-angiotensin-aldosterone pathway

activation

stressorschange 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

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

CORTISOL RELEASE Increases blood glucose Stronger sympathetic system effect on

heart rate Decreases nonessential energy-using

activities like: Hormone production

º Metabolic rate and reproductive functions decrease

Bone formation Red and white blood cell production

º Immune system becomes depressed

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.

ANSWER

d. Glucose provides energy.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.

ANTIDIURETIC HORMONE (ADH) Also called vasopressin Causes vasoconstriction Makes kidneys reabsorb water from

urine to blood

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

Blood pressure increased

Blood flow to skin, guts, and kidneys reduced

Skin becomes pale

Urine production decreases

GI activity decreases

epinephrine and norepinephrine

heart

increased HRincreased heart

strength

increased BP

blood vessels

vasoconstriction in skin, guts,

kidneys

SYMPATHETIC SYSTEM “FIGHT-OR-FLIGHT”RESPONSE

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

RENIN-ANGIOTENSIN-ALDOSTERONE PATHWAY (CONT.)

Angiotensin II: stronger vasoconstriction

Also stimulates the adrenal cortex

Aldosterone released

adrenal cortex

Angiotensin II

Aldosterone

QUESTION

True or False:Angiotensin-converting enzyme must be

present in order for aldosterone to be released by the adrenal gland.

ANSWER

TrueWithout angiotensin-converting enzyme,

angiotensin II would not be created. Angiotensin II stimulates the adrenal cortex to produce aldosterone.

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 volumeoliguria

secrete K+

= Very low urine output

stressorschange 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

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 glucoseQuestion: What should be fixed first? Why?

releases

which affect

release

which affect

Central Nervous System

hormones and neurotransmitters

immune cells

inflammatory mediators

STRESS “SNOWBALL” / POSITIVE FEEDBACK

EFFECTS OF STRESS ON THE IMMUNE SYSTEM

Decreased immune cell production Decreased thymus activity Changes in the kind of immune cells produced

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

ANSWER

d. All of the aboveStress 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.

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

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

Question: Do the stress responses solve the person’s

problem? Will negative feedback tell them when to turn

off?

ACUTE STRESS

Question: Which organs of the body would you expect to

see damaged by acute stress? Why?

RESULTS OF LONG-TERM STRESS Chronic stress

Sympathetic activity and cortisol are elevated Complications result from the reduced

immune response Posttraumatic stress disorder

Sympathetic system is activated Cortisol levels are decreased

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 shotQuestion:What about his case might be stress-related?

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?