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The sympathetic nervous system is responsible for priming the body for action, particularly in situations threatening survival. [16] One example of this priming is in the moments before waking, in which sympathetic outflow spontaneously increases in preparation for action.
This same sympathetic outflow is increased to the sinoatrial node in the atria, which causes increased heart rate/cardiac output. These cardiopulmonary receptors also inhibits vagal stimulation in the vasoconstrictor center of the medulla resulting in decreased release of angiotensin , aldosterone , and vasopressin .
This stimulates an afferent limb which activates central nervous system pathways that in turn exert two different but synergistic autonomic effects on the body. First, global sympathetic outflow is reduced and, second, vagal outflow is increased.
The sympathetic division emerges from the spinal cord in the thoracic and lumbar areas, terminating around L2-3. The parasympathetic division has craniosacral "outflow", meaning that the neurons begin at the cranial nerves (specifically the oculomotor nerve, facial nerve, glossopharyngeal nerve and vagus nerve) and sacral (S2-S4) spinal cord.
The white ramus communicans (pl.: rami communicantes) from Latin ramus (branch) and communicans (communicating) is the preganglionic sympathetic outflow nerve tract from the spinal cord. Each of the thoracic, and the first and second lumbar nerves contribute a white ramus communicans to the adjoining sympathetic ganglion , unlike the gray rami ...
This is set in motion via the adrenergic (sympathetic) outflow from the brain, but the heart is unable to meet requirements because of the low blood volume, or decreased return. A feedback response to the medulla is triggered via the afferent vagus nerve. The high (ineffective) sympathetic activity is thereby modulated by vagal (parasympathetic ...
This article lists rivers by their average discharge measured in descending order of their water flow rate. Here, only those rivers whose discharge is more than 2,000 m 3 /s (71,000 cu ft/s) are shown. It can be thought of as a list of the biggest rivers on Earth, measured by a specific metric.
Sympathetic nerve fibers travel around the tunica media of the artery, secrete neurotransmitters such as norepinephrine into the extracellular fluid surrounding the smooth muscle (tunica media) from the terminal knob of the axon. The smooth muscle cell membranes have α and β-adrenergic receptors for these neurotransmitters.