Stress

January 14, 2018 | Author: Anonymous | Category: Science, Health Science, Immunology
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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

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