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The neurotransmitters of postganglionic fibers differ: In the parasympathetic division , neurons are cholinergic . That is to say acetylcholine is the primary neurotransmitter responsible for the communication between neurons on the parasympathetic pathway .
Group C fibers include postganglionic fibers in the autonomic nervous system (ANS), and nerve fibers at the dorsal roots (IV fiber). These fibers carry sensory information. Damage or injury to nerve fibers causes neuropathic pain. Capsaicin activates C fibre vanilloid receptors, giving chili peppers a hot sensation.
There are two kinds of neurons involved in the transmission of any signal through the sympathetic system: pre-ganglionic and post-ganglionic. The shorter preganglionic neurons originate in the thoracolumbar division of the spinal cord specifically at T1 to L2~L3, and travel to a ganglion, often one of the paravertebral ganglia, where they synapse with a postganglionic neuron.
Cranial nerve ganglia contain the cell bodies of cranial nerve neurons. Autonomic ganglia contain the cell bodies of autonomic nerves. In the autonomic nervous system, fibers from the central nervous system to the ganglia are known as preganglionic fibers, while those from the ganglia to the effector organ are called postganglionic fibers.
The preganglionic neuron can travel superiorly or inferiorly to a sympathetic paravertebral ganglion of a higher or lower level where it can synapse with a postganglionic sympathetic neuron. From here, the postganglionic sympathetic neuron can travel back out the grey ramus communicans of that level to the mixed spinal nerve and on to an ...
The first neuron in this pathway is referred to as the preganglionic or presynaptic neuron. Its cell body sits in the central nervous system and its axon usually extends to synapse with the dendrites of a postganglionic neuron somewhere else in the body. The axons of presynaptic parasympathetic neurons are usually long, extending from the CNS ...
The grey rami communicantes exist at every level of the spinal cord and are responsible for carrying postganglionic nerve fibres from the paravertebral ganglia to their destination, and for carrying those preganglionic nerve fibres which enter the paravertebral ganglia but do not synapse. [citation needed] [1]
The postganglionic axons of the SCG innervate the pineal gland and are involved in circadian rhythm. [7] This connection regulates the production of the hormone melatonin, which regulates sleep and wake cycles, however the influence of SCG neuron innervation of the pineal gland is not fully understood. [8]