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 Energetics, Homeostasis and Stress

Phases of the stress response Alarm Phase Resistance Phase Exhaustion Phase

Alarm Phase: Catecholamines: epinephrine and norepineprhine Adrenal Gland Sympathetic Neuron epinephrine Releases norepineprhine onto these tissues

Epinephrine and Stress

Catecholamines--what do they do? –Increase blood glucose levels –Increase oxygen in circulation –Increase heart rate –Alters blood supply— ↑ to brain and muscles

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

Pre-storm (n=3) Storm (n=8) Calm (n=8) Time after capture (min) Corticosterone, ng/ml

Effects of Glucocorticoids 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 Emergency Life History Stage

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

glucose mobilization Breakdown of protein to make glucose Inhibit immune system Decreased parental care Decrease reproduction Energy depletion Muscle wasting Increase parasite load, can’t fight disease, infection Loss of young Total loss of fitness for the season Acute Responses to StressChronic Stimulation

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 Energetics, Homeostasis and Stress

Modulation of the adrenocortical response to stress Is it always adaptive to respond hormonally to stress? Effect of Breeding Environment Effect of Parental Responsibility Effect of Body Condition

Modulation of the adrenocortical response to stress Is it always adaptive to respond hormonally to stress? Effect of Breeding Environment Effect of Parental Responsibility Effect of Body Condition

Corticosterone and Body Condition fence lizard

Modulation of the adrenocortical response to stress Is it always adaptive to respond hormonally to stress? Effect of Breeding Environment Effect of Parental Responsibility Effect of Body Condition

PESASESAWESAREPH Males Females Magnitude ofCorticosterone Increase, ng/ml Pectoral Sandpiper Semipalmated Sandpiper Red Phalarope F M + F MParental care? :

Modulation of the adrenocortical response to stress Is it always adaptive to respond hormonally to stress? Effect of Breeding Environment Effect of Parental Responsibility Effect of Body Condition

Breeding Environment

Time after capture (mintues) CORT (ng/ml) BENIGN BREEDING ENVIRONMENT HARSH BREEDING ENVIRONMENT winter summer summer winter Cactus Wren Black-throated sparrow Abert's Towhee summer winter Inca Dove

Modulation of the adrenocortical response to stress Is it always adaptive to respond hormonally to stress? Effect of Breeding Environment Effect of Parental Responsibility Effect of Body Condition

Phases of the stress response –Time frame of hormonal response Modulation of the Stress Response Energetics, Homeostasis and Stress

Energy and Homeostasis: Definitions Homeostasis: maintenance of basic systems essential for life: pH, glucose, temp, salts, oxygen But: homeostasis must be supported as environmental conditions or life history stage changes……SO: –Basic—maintenance of basic systems –Regulated— homeostasis through life history changes –Facultative— homeostasis under non-ideal conditions or unpredictable changes Stress: when energy required to maintain homeostasis is greater than the energy available (negative energy balance)

Energy E E = The energy required to maintain homeostasis (basic existence) E I = The energy required to maintain normal function under ideal conditions E O = extra energy required under non- ideal conditions E G = Energy available in the environment

EIEI E ENERGY TIME E I = normal function—ideal conditions regulated homeostasis E E = basic existencehomeostasis E O = function—non-ideal conditions facultative homeostasis Energy Model homeostasis Regulated homeostasis Facultative Homeostasis

EIEI E ENERGY TIME E I = normal function—ideal conditions regulated homeostasis E E = basic existencehomeostasis E O = function—non-ideal conditions facultative homeostasis Energy Model homeostasis Regulated Homeostasis Facultative Homeostasis

EiEi E ENERGY TIME EGEG E G = energy available E i = normal function—ideal conditions regulated homeostasis E E = basic existencehomeostasis E O = function—non-ideal conditions facultative homeostasis Energy Model homeostasis Regulated Homeostasis Facultative Homeostasis Negative Energy Balance ELHS

EGEG EiEi E Negative Energy Balance EOEO ENERGY TIME E G = energy available E i = normal function—ideal conditions E E = basic existence E O = function—non-ideal conditions Energy Model homeostasis Regulated Homeostasis Time to change strategy (ELHS) ● seasonal change ● breeding ● predator pressure ● parasite load ● human disturbance ● change in social status ● change in energetic reserves Facultative Homeostasis

EGEG EIEI E EOEO EGEG EIEI E EOEO Energy Models ENERGY