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Posts Tagged ‘innervation’

N.Vagus

July 15, 2010 3 comments

An article on vagus nerve.

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The vagus nerve is the tenth cranial nerve. It has the most extensive distribution of any of the cranial nerves and contains sensory, motor and parasympathetic fibers. The vagus emerges from the brain stem at the medulla oblongata, between the olive and the inferior cerebellar peduncle. It exits the cranium through the jugular foramen with the glossopharyngeal and accessory nerves. The vagus nerve has two ganglia, the superior and inferior ganglia. The superior ganglion lies within the jugular foramen. The inferior ganglion is situated just below. Just below the inferior ganglion, the vagus is joined by the cranial part of the accessory nerve. The vagus then passes downwards within the carotid sheath and enters the thorax at the root of the neck.

Sympathetic Nerves, N.Phrenicus and Nn.Splanchnici


An article on sympathetic nerves, phrenic and splanchnic nerves.

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The sympathetic ganglia are swellings along the length of the pair of sympathetic trunks running longitudinally on either side of the vertebral column. The sympathetic trunks are located anterior to the cervical transverse processes, anterior to the heads of the ribs, on the antero- lateral aspects of the lumbar vertebral bodies, on the anterior aspect of the sacrum (medial to the ventral sacral foramina) and on the front of the coccyx. They are located at the site of synapses between the preganglionic and postganglionic neurons. There are a variable number of ganglia, approximately two (or three) cervical, eleven thoracic, four lumbar, four sacral and one coccygeal. The ventral rami of all spinal nerves are connected to the sympathetic trunk by gray rami communicantes. The ventral rami of T1 to L2 (L3) are also connected to the sympathetic trunk by white rami communicantes.

Superior Cervical Ganglia


An article on superior cervical ganglia.

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The superior cervical ganglion is the largest of the cervical ganglia and consists of the fused ganglia of C1 to C4. It is situated at the level of the second and third cervical vertebrae, anterior to the longus capitis muscle and posterior to the internal carotid artery and its carotid sheath. It is connected to the middle cervical ganglion inferiorly by the sympathetic trunk. It gives rise to lateral, medial and anterior branches. The lateral branches of the superior cervival ganglion consist of gray rami communicantes, which pass to the four upper cervical spinal nerves, the inferior vagal ganglion and hypoglossal nerve (XII cranial nerve). The jugular nerve ascends to the base of the skull and divides to join the inferior glossopharyngeal and superior vagal ganglia; other fibers reach the superior jugular bulb and meninges of the posterior cranial fossa.

The Course of N.ulnaris


A short article on the course of ulnar nerve.

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The ulnar nerve (C7, 8, T1) is the continuation of the medial cord of the brachial plexus. It is usually joined in the axilla by fibers from C7. The ulnar nerve is motor to most of the small muscles of the hand, to flexor carpi ulnaris, and to the ulnar half of the flexor digitorum profundus. It provides sensibility to the ulnar aspect of the hand.

The Course of N.radialis


A short article on the course of radial nerve.

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The radial nerve is the direct continuation of the posterior cord (C5-T1) of the brachial plexus. It supplies the muscles of the extensor compartments, the skin overlaying them and the skin over the dorusm od the hand.

The Course of N.medianus


A short article on the course of median nerve.

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The median nerve (C5, 6, 7, 8, T1) is motor to most of the long flexors of the forearm and muscles of the thenar eminence. It supplies sensibility to the skin of the palm, (usually) radial three and half digits, elbow, wrist, and hand joints.

The Innervation of the Heart


An article on the innervation of the heart muscle.

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Initiation of the cardiac cycle is myogenic, originating in the sinuatrial node (SA). It is harmonizied in rate, force and output by autonomic nerves which operate on the nodal tissues and their prolongations, on coronary vessels and on the working atrial and ventricular musculature. All the cardiac branches of the N.vagus, X. cranial nerve, (parasympathetic) and all the sympathetic branches (except the cardiac branch of the superior cervical sympathetic ganglion) contain both afferent and efferent fibres; the cardiac branch of the superior cervical sympathetic ganglion is entirely efferent. Sympathetic fibres accelerate the heart and dilate the coronary arteries when stimulated, whereas parasympathetic (vagal) fibres slow the heart and cause constriction of coronary arteries.