STRESS
• Stress (ambiguous term):
– The event: A threat (real or implied) to homeostasis
(often called a stressor)
– The response: the physiological response to the threat
– The condition: the physiological state that results
• Stressors
– Physiological stress
– Physical stress
– Emotional stress
• Phases of the stress response
– Time frame of hormonal response
• Modulation of the Stress Response
• Stress in Humans: How can we cope?
Phases of the stress response
• Alarm Phase
• Resistance Phase
• Exhaustion Phase
Alarm Phase:
Catecholamines: epinephrine and norepineprhine
Sympathetic Neuron
Releases norepineprhine
onto these tissues
Adrenal Gland
epinephrine
Epinephrine and Stress
Catecholamines--what do they do?
– Metabolic:
– Cardiovascular:
– Respiratory:
Phases of the stress response
• Alarm Phase
• Resistance Phase
• Exhaustion Phase
hypothalamus
pituitary
adrenal
Glucocorticoids
(cortisol, corticosterone
Common Diving
Petrel near the
South
Georgia Islands
Calm (n=8)
Pre-storm (n=3)
Storm (n=8)
Corticosterone, ng/ml
90
80
70
60
50
40
30
20
10
0
0
10
20
30
40
Time after capture (min)
50
60
Two Examples from Human Studies
Adult men
Kids
Kirschbaum et al., 1995
Buske-Kirschbaum et al., 1997
Effects of Glucocorticoids
Emergency
Life History Stage
•
•
•
•
•
Increase circulating glucose
Suppress the immune system
Suppress reproductive behavior
Suppress growth
Multiple behavioral effects, dependent on
species…
– e.g.
• Induce territory abandonment
• Increase foraging
• Reduce parental care
The stress response
alarm and resistance
• Maximizes glucose in the
blood
• Maximizes glucose and
oxygen delivery to critical
tissues
• Shuts down non-critical
activities (redirects physiology
and behavior)
– Digestion
– Reproduction
– Growth
Phases of the stress response
• Alarm Phase
• Resistance Phase
• Exhaustion Phase
ACUTE RESPONSES TO STRESS
CHRONIC STIMULATION
•
Artherosclerotic plaques, heart
disease, embolisms, strokes
•
Muscle wasting
•
Insulin insensitivity (NIDDM)
•
Infertility, shut-down of
reproductive axis
Shut-down digestion
•
Ulcers, irritable bowel syndrome
Inhibit immune system
•
Degeneration of immune tissues
•
Neural degeneration
•
High pulse rate, elevated blood
pressure
•
Breakdown of protein for
gluconeogenesis
•
Hyperglycemia, insulin
suppression
•
Decrease reproduction
•
•
Binding Globulins
Do corticosteroid binding globulins change in response to stress?
Social Stress (CBG)
2500
CBG (nM)
2000
*
1500
1000
500
0
control
winner
loser
Phases of the stress response
• Alarm Phase
– Activated in seconds
• Resistance Phase
– Activated in minutes
• Exhaustion Phase
– Chronic stimulation of Catecholamines
and Glucocorticoids
• Phases of the stress response
– Time frame of hormonal response
• Modulation of the Stress Response
• Stress in Humans: How can we
cope?
Modulation of the adrenocortical response
to stress
Is it always adaptive to respond hormonally to stress?
Effect of Body Condition
Effect of Parental Responsibility
Effect of Breeding Environment
Modulation of the adrenocortical response
to stress
Is it always adaptive to respond hormonally to stress?
Effect of Body Condition
Effect of Parental Responsibility
Effect of Breeding Environment
Corticosterone and Body Condition
fence lizard
Modulation of the adrenocortical response
to stress
Is it always adaptive to respond hormonally to stress?
Effect of Body Condition
Effect of Parental Responsibility
Effect of Breeding Environment
F
Parental care? :
M
M+F
Magnitude of
Corticosterone Increase, ng/ml
80
60
Males
Females
40
20
0
9
11
8
Pectoral
Sandpiper
PESA
SESA
13
Semipalmated
Sandpiper
8
WESA
5
Red
Phalarope
REPH
Modulation of the adrenocortical response
to stress
Is it always adaptive to respond hormonally to stress?
Effect of Body Condition
Effect of Parental Responsibility
Effect of Breeding Environment
Breeding Environment
40
Abert's Towhee
40
summer
winter
30
BENIGN
BREEDING
ENVIRONMENT
50
Inca Dove
30
20
20
CORT (ng/ml)
10
0
60
10
1
5
10
30
60
Black-throated sparrow
50
HARSH
BREEDING
ENVIRONMENT
1
5
10
30
60
Cactus Wren
50
40
winter
40
0
summer
winter
summer
30
30
20
20
10
10
0
0
1
5
10
30
60
1
5
Time after capture (mintues)
10
30
60
Modulation of the adrenocortical response
to stress
Is it always adaptive to respond hormonally to stress?
Effect of Body Condition
Effect of Parental Responsibility
Effect of Breeding Environment