The effects of the sympathetic nervous system on target organs include mydriasis, increased heart rate, contractility, and conduction velocity, bronchodilation, sweat secretion, decreased intestinal motility, and increased renin release. The sympathetic and parasympathetic nervous systems have antagonistic effects in some organ systems. The sympathetic preganglionic fibers stimulate the chromaffin cells of the adrenal medulla directly via acetylcholine on nicotinic receptors, which results in the release of norepinephrine and epinephrine mediating the fight or flight response. The adrenal medulla does not have a postsynaptic neuron. All postganglionic fibers of the sympathetic division are adrenergic fibers (release norepinephrine) that act on adrenergic alpha or beta receptors for neurotransmission, with the exception of the fibers innervating the sweat glands, which are cholinergic. The preganglionic fibers of both ANS divisions and the postganglionic fibers of the parasympathetic division are cholinergic fibers (release acetylcholine) that act on cholinergic receptors (nicotinic or muscarinic). The sympathetic and parasympathetic nervous systems consist of preganglionic and postganglionic neurons. The sympathetic nervous system has a thoracolumbar outflow and is activated during fight or flight response, while the parasympathetic nervous system has a craniosacral outflow and is activated during digestion and rest. It is divided into the sympathetic and parasympathetic nervous systems. The autonomic nervous system (ANS) is part of the peripheral nervous system and regulates involuntary, visceral body functions in different organ systems (e.g., the cardiovascular, gastrointestinal, genitourinary systems).
0 Comments
Leave a Reply. |