Sympathetic and Parasympathetic Nervous Systems Essay

Sympathetic and Parasympathetic Nervous Systems - Essay ExampleThe nerve fibers of theparasympathetic nervous systemare thecranial nerves, primarily thevagus nerve, and the lumbar spinal nerves. When stimulated, these nerves increase digestive secretions and reduce the mallbeat.The sympathetic nervous system activates what is often termed the fight or flying response. Like other recesss of the nervous system, the sympathetic nervous system operates through a series of interconnected neurons. Sympathetic neurons are frequently considered better of the peripheral nervous system (PNS), although there are many that lie within the central nervous system (CNS). Sympathetic neurons of the spinal cord (which is part of the CNS) communicate with peripheral sympathetic neurons via a series of sympathetic ganglia. Within the ganglia, spinal cord sympathetic neurons join peripheral sympathetic neurons through chemic synapses. Spinal cord sympathetic neurons are therefore called presynaptic (or preganglionic) neurons, while peripheral sympathetic neurons are called postsynaptic (or postganglionic) neurons. At synapses within the sympathetic ganglia, preganglionic sympathetic neurons release acetylcholine, a chemical messenger that binds and activates nicotinic acetylcholine receptors on postganglionic neurons. In response to this stimulus, postganglionic neurons principally release noradrenalin (norepinephrine). Prolonged activation can elicit the release of adrenaline from the adrenal medulla. Once released, noradrenalin and adrenaline bind adrenergic receptors on peripheral tissues. Binding to adrenergic receptors causes the effects seen during the fight-or-flight response. These include pupil dilation, increased sweating, increased heart rate, and increased blood pressure. Sympathetic nerves originate inside the vertebral column, toward the middle of the spinal cord in the