| Postganglionic nerve fibers | |
|---|---|
 Sympathetic connections of the ciliary and superior cervical ganglia. | |
| Details | |
| Identifiers | |
| Latin | neurofibrae postganglionicae |
| TA98 | A14.2.00.010 |
| FMA | 76569 |
| Anatomical terms of neuroanatomy | |
In the autonomic nervous system, nerve fibers from the ganglion to the effector organ are called postganglionic nerve fibers.
The neurotransmitters of postganglionic fibers differ:
A ganglion is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system, this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system, there are both sympathetic and parasympathetic ganglia which contain the cell bodies of postganglionic sympathetic and parasympathetic neurons respectively.
The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates internal organs, smooth muscle and glands. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, its force of contraction, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response.
The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.
The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.
The adrenal medulla is the inner part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of chromaffin cells that secrete catecholamines, including epinephrine (adrenaline), norepinephrine (noradrenaline), and a small amount of dopamine, in response to stimulation by sympathetic preganglionic neurons.
Chromaffin cells, also called pheochromocytes, are neuroendocrine cells found mostly in the medulla of the adrenal glands in mammals. These cells serve a variety of functions such as serving as a response to stress, monitoring carbon dioxide and oxygen concentrations in the body, maintenance of respiration and the regulation of blood pressure. They are in close proximity to pre-synaptic sympathetic ganglia of the sympathetic nervous system, with which they communicate, and structurally they are similar to post-synaptic sympathetic neurons. In order to activate chromaffin cells, the splanchnic nerve of the sympathetic nervous system releases acetylcholine, which then binds to nicotinic acetylcholine receptors on the adrenal medulla. This causes the release of catecholamines. The chromaffin cells release catecholamines: ~80% of adrenaline (epinephrine) and ~20% of noradrenaline (norepinephrine) into systemic circulation for systemic effects on multiple organs, and can also send paracrine signals. Hence they are called neuroendocrine cells.
The nucleus ambiguus is a group of large motor neurons, situated deep in the medullary reticular formation named by Jacob Clarke. The nucleus ambiguus contains the cell bodies of neurons that innervate the muscles of the soft palate, pharynx, and larynx which are associated with speech and swallowing. As well as motor neurons, the nucleus ambiguus contains preganglionic parasympathetic neurons which innervate postganglionic parasympathetic neurons in the heart.
Muscarinic acetylcholine receptors, or mAChRs, are acetylcholine receptors that form G protein-coupled receptor complexes in the cell membranes of certain neurons and other cells. They play several roles, including acting as the main end-receptor stimulated by acetylcholine released from postganglionic fibers. They are mainly found in the parasympathetic nervous system, but also have a role in the sympathetic nervous system in the control of sweat glands.
The pterygopalatine ganglion is a parasympathetic ganglion in the pterygopalatine fossa. It is one of four parasympathetic ganglia of the head and neck,.
The ciliary ganglion is a parasympathetic ganglion located just behind the eye in the posterior orbit. It is 1–2 mm in diameter and in humans contains approximately 2,500 neurons. The ganglion contains postganglionic parasympathetic neurons. These neurons supply the pupillary sphincter muscle, which constricts the pupil, and the ciliary muscle which contracts to make the lens more convex. Both of these muscles are involuntary since they are controlled by the parasympathetic division of the autonomic nervous system.
Hexamethonium is a non-depolarising ganglionic blocker, a neuronal nicotinic (nAChR) receptor antagonist that acts in autonomic ganglia by binding mostly in or on the nAChR receptor, and not the acetylcholine binding site itself. It does not have any effect on the muscarinic acetylcholine receptors (mAChR) located on target organs of the parasympathetic nervous system, nor on the nicotinic receptors at the skeletal neuromuscular junction, but acts as antagonist at the nicotinic acetylcholine receptors located in sympathetic and parasympathetic ganglia (nAChR).
The submandibular ganglion is part of the human autonomic nervous system. It is one of four parasympathetic ganglia of the head and neck..
Each spinal nerve receives a branch called a gray ramus communicans from the adjacent paravertebral ganglion of the sympathetic trunk. The gray rami communicantes contain postganglionic nerve fibers of the sympathetic nervous system and are composed of largely unmyelinated neurons. This is in contrast to the white rami communicantes, in which heavily myelinated neurons give the rami their white appearance.
In the autonomic nervous system, nerve fibers from the central nervous system to the ganglion are known as preganglionic nerve fibers. All preganglionic fibers, whether they are in the sympathetic division or in the parasympathetic division, are cholinergic and they are myelinated.
The celiac ganglia or coeliac ganglia are two large irregularly shaped masses of nerve tissue in the upper abdomen. Part of the sympathetic subdivision of the autonomic nervous system (ANS), the two celiac ganglia are the largest ganglia in the ANS, and they innervate most of the digestive tract.
The lateral grey column is one of the three grey columns of the spinal cord ; the others being the anterior and posterior grey columns. The lateral grey column is primarily involved with activity in the sympathetic division of the autonomic motor system. It projects to the side as a triangular field in the thoracic and upper lumbar regions of the postero-lateral part of the anterior grey column.
Small intensely fluorescent cells are the interneurons of the sympathetic ganglia of the Sympathetic division of the autonomic nervous system (ANS). The neurotransmitter for these cells is dopamine. They are a neural crest derivative and share a common sympathoadrenal precursor cell with sympathetic neurons and chromaffin cells.
The lumbar ganglia are paravertebral ganglia located in the inferior portion of the sympathetic trunk. The lumbar portion of the sympathetic trunk typically has 4 lumbar ganglia. The lumbar splanchnic nerves arise from the ganglia here, and contribute sympathetic efferent fibers to the nearby plexuses. The first two lumbar ganglia have both white and gray rami communicates.
The sympathoadrenal system is a physiological connection between the sympathetic nervous system and the adrenal medulla and is crucial in an organism's physiological response to outside stimuli. When the body receives sensory information, the sympathetic nervous system sends a signal to preganglionic nerve fibers, which activate the adrenal medulla through acetylcholine. Once activated, norepinephrine and epinephrine are released directly into the blood by adrenomedullary cells where they act as the bodily mechanism for "fight-or-flight" responses. Because of this, the sympathoadrenal system plays a large role in maintaining glucose levels, sodium levels, blood pressure, and various other metabolic pathways that couple with bodily responses to the environment. During numerous diseased states, such as hypoglycemia or even stress, the body's metabolic processes are skewed. The sympathoadrenal system works to return the body to homeostasis through the activation or inactivation of the adrenal gland. However, more severe disorders of the sympathoadrenal system such as pheochromocytoma can affect the body's ability to maintain a homeostatic state. In these cases, curative agents such as adrenergic agonists and antagonists are used to modify epinephrine and norepinephrine levels released by the adrenal medulla.
The ciliary ganglion is a parasympathetic ganglion located just behind the eye in the posterior orbit. Three types of axons enter the ciliary ganglion but only the preganglionic parasympathetic axons synapse there. The entering axons are arranged into three roots of the ciliary ganglion, which join enter the posterior surface of the ganglion.
