Neuroendocrine Response To Stress

D i.e. Insulin

A i.e. Epinephrine; B i.e. GH; C i.e. Glucocorticoid

Glucagon, catecholamines (epinephrine & norepinephrine), cortisol, ACTH, GH (growth hormone) are increased in stress (infection, surgery, hypoglycemia) whereas, insulin is suppressed (decreased)Q.

• In maintenance of internal homeostasis (ie avoiding stress) and reproduction processes, multiple hormones cooperate to bring about organized biochemical & physiological responses.

Stress Syndrome: CRH – ACTH – Cortisol Axis

• The primitive signal of glucose (substrate) lack is expanded to a broder signal of fright or stress and evokes a coordinated neural and endocrine response. Any stressful event eg. surgery, infection, burn triggers a hypermetabolic state in which a resting energy expenditure is increased alongwith body temperature.
• CRH-ACTH – cortisol axis is central to this integrated response to stress.

• Features of Stress Syndrome

  – Corticotropin releasing hormone (CRH) is increased in response to noxious environmental stimuli like pain, trauma,

  hypoglycemia, infection, surgery, hypovolemia. Various nervous impulses using several neuro transmitters (NTs) like norepinephrine, serotonin, acetylcholine, dopamine, and GABA reach CRH neurosecretory cells and cause release of CRH

  -In response to CRH, both ACTH and p endorphins (secreted 13-LPH & mature p-endorphin) are released in equimolar quantities 13-endorphin produce central analgesic response.

  – Glucagon & catecholamines (epinephrine & norepinephrine) are increased, stimulating glycogenolysis (glucose

  production in liver) for immediate use by critical organs such as the brain.

  -Cortisol production is increased in adrenal cortex which induces gluconeogenesis (glucose production from noncarbohydrate source like muscles & other body proteins)

  – Glucogon, epinephrine, ACTH and growth hormone (GH) stimulate lipolysis and free fatty acids (FFA) & ketones are

  released into the circulation to be used as an alternative metabolic fuel.

  –Insulin is suppressedQ that results in decrease in glucose utilization.

  -One form of stress that is cold, specially in neonate causes increased TRH secretion due to depressed metabolism of neurons in pre- optic area by cooling which release inhibitory discharge, permitting TRH secretion.

  -ADH (vasopressin), angiotensin & aldosterone synthesis is increased enhancing salt water retention

  -So increased glucose production (by glycogenolysis & gluconeogenesis) and decreased utilization of glucose results in hyperglycemia. There is marked increase in release of aminoacids from tissue protein, particularly from skeletal muscle for gluconeogenesis. However, synthesis of specific proteins may increase

  -These metabolic changes are coordinated with increased sympathetic nervous system activity causing peripheral vasoconstriction and increased blood pressure.

B i.e. Glucagon

A i e. Neoglucogenesis C i.e. Protein breakdown

It is a catabolic hormone. Their function appears to be oriented to maintain blood glucose levels during starvation – so that brain continues to get its nutrients.

*  In stress vasopressinQ also increases Glucocorticoids

*  Glucocorticoids inhibit intestinal absorption & enhance renal excretion of Ca++

*  In adrenal insufficiency, the blood glucose is normal as long as food intake is maintained, but fasting precipitates hypoglycemia & collapse. This is because glucocorticoids are necessary for glucagons to exert its gluconeogenic action during fasting.

B i.e. Vasopressin; C i.e. Adrenaline

Ans: B i.e. Insulin

Due to stress, the hypothalamus is stimulated —> CRH secretion increased ACTH secretion increased Cortisol secretion increased

Satyanarayana’s Biochemistry, 3rd ed., p-671 states

• In emergency situations like stress, extreme exercise and trauma, the nervous system stimulates adrenal medulla to release epinephrine. Epinephrine suppresses insulin release and promotes energy metabolism
• Sympathetic stimulation causes stimulation of adrenal medulla so that adrenal medulla secretes vigorous amount of adrenalin and noradrenalin.

Ans. B: Increased insulin

Most of the stressful stimuli that increase ACTH secretion also activate the sympathetic nervous system

Alpha adrenergic stimulators (epinephrine and norepinephrine) inhibits insulin secretion

The condition in which sympathetic nervous system, including the sympatho-adrenal medullary system is activated are: fear, trauma, haemorhhage, fluid loss etc.

Stressful stimuli stimulates secretion of growth hormone in humans

Stress hormones

• They are cortisol, GH and norepinephrine
• They are released at periods of high stress.

• Stress hormones rise in the body during any neuroendocrine reaction such as surgery and they remain high as long as 72 hours, after which all these hormones return to their normal level, the last being cortisol.
• Stress hormones act by mobilizing energy from storage to muscles, increasing heart rate, blood pressure and breathing rate and shutting down metabolic processes such as digestion, reproduction, growth and immunity.

Stress response to surgery

• It is characterized by increased secretion of pituitary hormones and activation of the sympathetic nervous system.
• The changes in pituitary secretion have secondary effects on hormone secretion from target organs.
• For example, release of corticotrophin from the pituitary stimulates cortisol secretion from the adrenal cortex.
• Arginine vasopressin is secreted from the posterior pituitary and has effects on the kidney.
• In the pancreas, glucagon is released and insulin secretion may be diminished.
• The overall metabolic effect of the hormonal changes is increased catabolism which mobilizes substrates to provide energy sources, and a mechanism to retain salt and water and maintain fluid volume and cardiovascular homeostasis.