![]() ![]() In humans, chronic stress results in long-term stimulation of the fight-or-flight response, which leads to constant production and secretion of catecholamines (e.g., epinephrine) and hormones such as cortisol. ![]() Salivary glands work through small volume potassium and water secretion. ![]() Kidney increases renin secretion to increase intravascular volume.Urinary bladder, there is relaxation of the detrusor muscle and contraction of the urethral sphincter to help stop urine output during sympathetic activation.Exocrine and endocrine pancreas decreases both enzyme and insulin secretion.Stomach and intestines, decreased motility and sphincter contraction, as well as contraction of the gallbladder, occur to slow down digestion to divert energy to other parts of the body.Lungs, bronchodilation and decreased pulmonary secretions occur to allow more airflow through the lungs.Heart, sympathetic activation causes an increased heart rate, the force of contraction, and rate of conduction, allowing for increased cardiac output to supply the body with oxygenated blood.The ciliary muscle relaxes, allowing for far vision to improve. Eye, sympathetic activation causes the radial muscle of the iris to contract, which leads to mydriasis, allowing more light to enter.The effects in which SNS acts in direct contrast to the PNS function include the following: eg, the sympathetic nervous system can accelerate heart rate, widen bronchial passages, decrease motility (movement) of the large intestine, constrict blood vessels, cause pupil dilation, activate goose bumps, start sweating and raise blood pressure. Efferent messages can trigger changes in different parts of the body simultaneously. Messages travel through the SNS in a bidirectional flow. The actions of the sympathetic nervous system occur in concert with other neural or hormonal responses to stress eg increases in corticotropin and cortisol secretion. ![]()
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