Download Chap - Physiology of Stress

PHYSIOLOGY OF STRESS
Physiology III, Tri 4
Mrs. Brashear
Resources for this lecture topic:
Medical Physiology, Guyton & Hall
Human Physiology, Vander
Physiological Basis of Medical Practice, Best & Taylor
Physiology, Berne & Levy
Handbook of Stress, Medicine & Health, Cooper (Library)
Objectives:
1. To define stress.
2. To learn the types of responses to stress.
3. To understand the acute stress response.
4. To understand the pathology of chronic stress.
5. To review stress management
I. Stress defined
A. Organism’s reaction to every kind of strain, challenge or demand which elicits
a physiological response.
B. Types of stress
1. physical trauma
2. prolonged exposure to cold
3. prolonged heavy exercise
4. infection
5. decreased oxygen supply
6. pain
7. fright
8. emotional stress
9. shock
II. Responses to Stress
A. Emotional reactions
1. anxiety
2. depression
3. apathy
4. alienation
5. hypochondriasis
6. etc.
B. Behavioral reactions
1. smoking
2. drinking
3. taking risks
4. aggressive behavior
5. antisocial behavior
C. Physiological reactions
1. Integrated response to stress that is protective
a. mental
b. physical
2. Neuroendocrine response
a. Sympathetics
b. Adrenal cortex and medulla
III. Acute Stress Response
Allows survival under numerous adverse conditions
A. Function of Stress response
B. Role of a Mass Sympathetic Response
(Guyton, page 778)
“fright or flight” = alarm or stress reaction
MASS SYMPATHETIC RESPONSE
(PARASYMPATHETIC INHIBITION)
Sympathetic Stimulation
Norepinephrine
 receptors -1 receptors
action:
action:
vasoconstriction of
vascular smooth
muscle
 heart rate
contractility
 conduction velocity
Adrenal Glands
Norepinephrine
Epinephrine
 receptors
High levels:
vasoconstriction
1. Role of hypothalamus
2. Widespread reaction
3. Intent
4. Mechanisms:
a. cardiac
b. blood
c. ventilation
d. coagulation of blood
e. muscle
f. muscle and liver glycogenolysis
g. mental alertness
C. Role of the Hypothalamic-Pituitary-adrenocortical axis
Or the CRH-ACTH-cortisol axis
1. Hormones involved
a. ACTH
b. catecholamines
c. ADH
-2 receptors
Normal levels:
vasodilatation
d. angiotensin
e. aldosterone
f. glucagon
g. GH
h. cortisol
2. Stress syndrome pathway
a. Hypothalamus
Pituitary
(CRH)
(ACTH)
Hypothalamus
adrenocortical axis
(cortisol)
CRH
Anterior Pituitary
STRESS
ACTH
Adrenal Cortex
cortisol
INPUT FROM OTHER BRAIN AREAS
HYPOTHALAMUS
CRH SECRETION
PLASMA CRH
ANTERIOR PITUITARY
ACTH SECRETION
PLASMA ACTH
ADRENAL CORTEX
CORTISOL SECRETION
PLASMA CORTISOL
TARGET CELL OF CORTISOL
RESPONSE TO CORTISOL
b. General function of the axis
STRESSORS
STRESS SIGNALS
Cortex, limbic
system, reticular
formation
Hypothalamus
norepinephrine
neurons
CRH
neurons
CRH
neurons
Cortisol
Sympathetic
neurons
Pituitary Spinal Cord
ACTH
adrenal gland
Arousal, behavioral
Cortex
Cortisol
Medulla
Epinephrine
activation
aggressiveness
Feeding and
sexual activity
Excitatory
Inhibitory
Growth and
reproductive
function
Local
injury
+ energy mobilization & redistribution
CV responsiveness to norepinephrine
Mental changes
Increased awareness of pain
Energy mobilization
redistribution
cardiovascular
responsiveness
Inflammation
Immune response
Visceral
function
- Feeding, growth
sexual activity, reproduction
inflammation & immune response
visceral function
D. Effects of Cortisol during stress
Normal homeostasis –
Stress –
Food
Calories
ADIPOSE TISSUE
Triglycerides
Lipolytic hormones Insulin
Free Fatty Acids
Glucose
The effect of cortisol on
the overall flow of fuels.
Glycogen
Glucose P
Liver
Glucose precursors
Insulin
Glucose
Amino Acids
Muscle
Protein
1. Energy mobilization and redistribution
a. protein metabolism –
catabolism
synthesis
effect on muscles
b. glucose metabolism
inhibition of glucose uptake
gluconeogenesis
glycogen synthesis
c. Lipids
lipolysis
2. Cardiovascular function
enhanced cardiac function
enhanced vascular reactivity
decreased endothelial permeability
3. Fluid volume
ADH
Aldosterone
4. Inflammatory response blocks prostaglandin production
a. decreases vasodilation
b. decrease permeability of membranes
c. decrease migration of monocytes and lymphocytes
blocks leukotrienes
d. decrease in neutrophil function
e. decrease in phagocytosis and bacterial killing
Inflammatory Response
production of
Platelet activating
Phosphatidyl choline
Nitric oxide
Arachidonic acid
Prostaglandins
Vasodilation
Leukotrienes
Neutrophil
function
Permeability
Leukocyte trapping
= Inhibition by cortisol
5. Immune Response –
a. decrease in cellular and humoral immunity
b. decrease in interleukin 1 & 6
c. decrease tumor necrosis factor
Immune Response
Macrophage
Antigen
Phagocytosis
Bacterial killing
= Inhibition by Cortisol
Interleukin -1
Fever
T - cells
Tumor necrosis factor
Interleukin -2 & 6
T-cell proliferation
B-cell proliferation
Antibody production
6. GH and sex steroids
7. Thyroid hormones
IV. Chronic Stress Response
Chronic stress can lead to syndromes and/or pathologies based on behavioral,
neuroendocrine, autonomic and immunologic adaptation during stressful
situations
A. Physiological Changes Resulting from Chronic Stress
1. Endocrine-metabolic
a. catabolic activity - cholesterol and fatty acids
b. hyperglycemia
c. insulin secretion related to hyperglycemia
d. appetite – weight gain
e. cellular activity and repair
2. GI tract
a. mucosal protective barrier
b. colonic motility
3. Musculoskeletal
a. decreased lean body mass
b. osteoporosis
osteoblasts
calcium absorption
fibroblast activity
c. skin
d. growth and maturation in children
4. Capillary fragility
5. Immunity
a. shrinkage of the thymus
b. wound healing
c. leukocytes
d. suppression of 3 inflammatory cytokines
B. Linking Stress to Disease
Causative?
Increased activity in genetic tendencies?
1. muscle tension
2. GI symptoms
indigestion, vomiting, heartburn, irritable colon syndrome,
constipation, etc.
3. CV symptoms
arrhythmias, CAD, pain or tightness, palpitations, hypertension, stroke
sudden death
4. Respiratory
dyspnea and hyperventilation
5. CNS
insomnia, weakness, fatigue syndromes, faintness & headaches
6. Mental disorders such as anxiety, depression
7. Decreased Immune response
infection
latent oncogenic viruses
metastatic spread of cancer cells
newly transformed cancer cells
8. Sexual dysfunction
dysmenorrhea
frigidity and impotence
9. Dermatological problems
V. Stress Management
3 basic pathways in order of preference
A. Eliminate or modify stress producing situation or remove individual
B. Change social situation
C. Strengthen the person to stress
1. physical exercise
2. meditation
3. relaxation techniques
4. social support
VI. Use of cortisol medically
A. Anti-inflammatory
B. Side effects