What is the primary neurotransmitter of the parasympathetic nervous system quizlet?

Answer: The efferent pathway of the sympathetic nervous system is composed of two neurons, connected in series, that provide for communication between the central nervous system and the effector organ. Those neurons communicate with one another by synapsing within autonomic ganglia. The neurons that travel from the central nervous system to the sympathetic ganglia are the preganglionic neurons, while those that travel from the ganglia to the effector organ are the postganglionic neurons. The preganglionic neurons of the sympathetic nervous system emerge from the lateral horn of the spinal cord within the thoracic and lumbar (thoracolumbar) regions, and exit from the ventral root. The dorsal and ventral roots combine to form the spinal nerve. Thereafter, the organization of the sympathetic nervous system can be described in three ways, based upon anatomical differences. First, the most common arrangement involves a short preganglionic neuron (compared to the postganglionic neuron) that leaves the spinal nerve via a branch called the white ramus and enters one of several sympathetic ganglia. These ganglia are linked together to form a structure that parallels the spinal cord within the sympathetic chain. After entering the sympathetic chain, a preganglionic neuron may branch into several collateral axons that travel up and down the sympathetic trunk to synapse with other postganglionic neurons. Each of these postganglionic neurons travels to a particular effector organ. Thus, activation of the sympathetic nervous system typically produces a response that is widespread, affecting multiple organs simultaneously. The second anatomical arrangement of the sympathetic nervous system contains a long preganglionic fiber that innervates the adrenal medulla. In this case, the chromaffin cells of the adrenal medulla act as the postganglionic neuron. When stimulated, chromaffin cells release catecholamines into the blood (80% epinephrine, 20% norepinephrine, and trace amount of dopamine). This architecture reinforces the widespread effect of the sympathetic nervous system on the body. The final anatomical arrangement contains preganglionic neurons that synapse with postganglionic fibers in collateral ganglia located outside of the sympathetic trunk. One example is a ganglion within the digestive system called the celiac ganglion, which is innervated by a long preganglionic neuron and is located outside of the sympathetic trunk. This arrangement provides for some very specific activity particular to organs, although this type of arrangement is uncommon.

Answer: Preganglionic neurons from the parasympathetic nervous system originate from the brainstem and the sacral region of the spinal cord (craniosacral region). The parasympathetic nerves that leave the spinal cord do not join with the spinal nerve as occurs in the sympathetic nervous system. Instead, they join with other parasympathetic preganglionic fibers to form pelvic nerves. Generally speaking, preganglionic parasympathetic nerves are long (compared with the postganglionic nerves), traveling to a ganglion that is located near the effector organ. This arrangement is quite different from the sympathetic nervous system, where most preganglionic nerves are short and enter ganglia within the sympathetic trunk. Thus, the parasympathetic nervous system is able to exert more discrete effects than the sympathetic nervous system due to the lack of interconnection between ganglia. Four parasympathetic preganglionic neurons originate from cranial nerve nuclei located within the brainstem, which explains why some preganglionic parasympathetic nerves travel within cranial nerves. The vagus nerve (X) is one of the more important parasympathetic nerves, innervating the lungs, heart, stomach, etc. The other cranial nerves that contain preganglionic parasympathetic axons are the oculomotor (III), facial (VII), and glossopharyngeal nerves (IX).

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What is the primary neurotransmitter of the parasympathetic nervous system?

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