Sympathetic, Parasympathetic and Enteric Nervous Systems

Autonomic nervous system has sympathetic (SNS), parasympathetic (PNS), enteric nervous system (ENS) that regulate the body's unconscious actions, the body's fight or flight response, and the body to feed and breed. SNS signals travel by preganglionic neurons that release acetylcholine (ACh), activating nicotinic ACh receptors on postganglionic neurons releasing norepinephrine that activates adrenergic receptors (AR) on peripheral tissues. SNS: accelerate heart rate; widen bronchial passages; decrease motility of large intestine; constrict blood vessels; increase oesophagus peristalsis; cause pupillary dilation, piloerection like goose bumps, perspiration sweating, and raise blood pressure. The amygdala by corticotropin releasing hormone, activates the hypothalamic-pituitary-adrenal axis. SNS beta2 AR on CD4+T and B cells controls immunity. Immunotherapy started with vaccination against smallpox, Cancer stops immune responses. Brain regulates innate and adaptive immune responses. PNS controls the urinary bladder, ureters, anal sphincters, uterus, prostate, glands, vagina, penis. The ENS, contain 600 million neurons. There are adrenergic dense vesicles in retina.