|
Light-near Dissociation
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. The ciliary ganglion is one of four parasympathetic ganglia of the head. The others are the submandibular ganglion, pterygopalatine ganglion, and otic ganglion. Structure The ciliary ganglion contains postganglionic parasympathetic neurons that supply the ciliary muscle and the pupillary sphincter muscle. Because of the much larger size of the ciliary muscle, 95% of the neurons in the ciliary ganglion innervate it compared to the pupillary sphincter. Roots Thre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasympathetic Nervous System
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 autonomic nervous system is responsible for regulating the body's unconscious actions. The parasympathetic system is responsible for stimulation of "rest-and-digest" or "feed-and-breed" activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tears), urination, digestion, and defecation. Its action is described as being complementary to that of the sympathetic nervous system, which is responsible for stimulating activities associated with the fight-or-flight response. Nerve fibres of the parasympathetic nervous system arise from the central nervous system. Specific nerves include several cranial nerves, specifically the oculomotor nerve, facial nerve, glossopharyngeal nerve, and vagus nerve. Three spinal nerves ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superior Cervical Ganglion
The superior cervical ganglion (SCG) is the upper-most and largest of the cervical sympathetic ganglia of the sympathetic trunk. It probably formed by the union of four sympathetic ganglia of the cervical spinal nerves C1–C4. It is the only ganglion of the sympathetic nervous system that innervates the head and neck. The SCG innervates numerous structures of the head and neck. Structure The superior cervical ganglion is reddish-gray color, and usually shaped like a spindle with tapering ends. It measures about 3 cm in length. Sometimes the SCG is broad and flattened, and occasionally constricted at intervals. It formed by the coalescence of four ganglia, corresponding to the four upper-most cervical nerves C1–C4. The bodies of its preganglionic sympathetic afferent neurons are located in the lateral horn of the spinal cord. Their axons enter the SCG to synapse with postganglionic neurons whose axons then exit the rostral end of the SCG and proceed to innervate their targ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasympathetic Ganglia
Parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system. Most are small terminal ganglia or intramural ganglia, so named because they lie near or within (respectively) the organs they innervate. The exceptions are the four paired parasympathetic ganglia of the head and neck. Parasympathetic ganglia of the head and neck These paired ganglia supply all parasympathetic innervation to the head and neck. *ciliary ganglion (sphincter pupillae, ciliary muscle) *pterygopalatine ganglion (lacrimal gland, glands of nasal cavity) *submandibular ganglion ( submandibular and sublingual glands) *otic ganglion (parotid gland) Roots Each has three roots entering the ganglion and a variable number of exiting branches. * The motor root carries presynaptic parasympathetic nerve fibers ( GVE) that terminate in the ganglion and synapse with the postsynaptic fibers that, in turn, project to target organs. * The sympathetic root carries postsynaptic sympathetic fibers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autonomic Ganglia Of The Head And Neck
Autonomic can refer to: *Autonomic nervous system, a division of the peripheral nervous system that supplies smooth muscle and glands, and thus influences the function of internal organs *Autonomic computing Autonomic computing (AC) is distributed computing resources with self-management (computer science), self-managing characteristics, adapting to unpredictable changes while hiding intrinsic complexity to operators and users. Initiated by IBM in 2001 ..., the self-managing characteristics of distributed computing resources See also * Autonomy (other) {{disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parinaud Syndrome
Parinaud's syndrome is a constellation of neurological signs indicating injury to the dorsal midbrain. More specifically, compression of the vertical gaze center at the rostral interstitial nucleus of medial longitudinal fasciculus (riMLF). It is a group of abnormalities of eye movement and pupil dysfunction and is named for Henri Parinaud (1844–1905), considered to be the father of French ophthalmology. Signs and symptoms Parinaud's syndrome is a cluster of abnormalities of eye movement and pupil dysfunction, characterized by: * Paralysis of upwards gaze: Downward gaze is usually preserved. This vertical palsy is supranuclear, so doll's head maneuver should elevate the eyes, but eventually all upward gaze mechanisms fail. In the extreme form, conjugate down gaze in the primary position, or the "setting-sun sign" is observed. Neurosurgeons see this sign most commonly in patients with hydrocephalus. * Pseudo- Argyll Robertson pupils: Accommodative paresis ensues, and pupils ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Argyll Robertson Pupil
Argyll Robertson pupils (AR pupils) are bilateral small pupils that reduce in size on a near object (i.e., they accommodate), but do ''not'' constrict when exposed to bright light (i.e., they do not react). They are a highly specific sign of neurosyphilis; however, Argyll Robertson pupils may also be a sign of diabetic neuropathy. In general, pupils that accommodate but do not react are said to show light-near dissociation (i.e., it is the absence of a miotic reaction to light, both direct and consensual, with the preservation of a miotic reaction to near stimulus (accommodation/convergence)). AR pupils are extremely uncommon in the developed world. There is continued interest in the underlying pathophysiology, but the scarcity of cases makes ongoing research difficult. Pathophysiology The two different types of near response are caused by different underlying disease processes. '' Adie's pupil'' is caused by damage to ''peripheral'' pathways to the pupil (parasympathetic neu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adie Syndrome
Adie syndrome, also known as Holmes–Adie syndrome, is a neurological disorder characterized by a tonically dilated pupil that reacts slowly to light but shows a more definite response to accommodation (i.e., light-near dissociation). It is frequently seen in females with absent knee or ankle jerks and impaired sweating. The syndrome is caused by damage to the postganglionic fibers of the parasympathetic innervation of the eye, usually by a viral or bacterial infection that causes inflammation, and affects the pupil of the eye and the autonomic nervous system. It is named after the British neurologists William John Adie and Gordon Morgan Holmes, who independently described the same disease in 1931. Signs and symptoms Adie syndrome presents with three hallmark symptoms, namely at least one abnormally dilated pupil (mydriasis) which does not constrict in response to light, loss of deep tendon reflexes, and abnormalities of sweating. Other signs may include hyperopia du ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denervation Supersensitivity
Denervation supersensitivity/Denervation hypersensitivity is the sharp increase of sensitivity of postsynaptic membranes to a chemical transmitter after denervation Denervation is any loss of nerve supply regardless of the cause. If the nerves lost to denervation are part of neural communication to an organ system or for a specific tissue function, alterations to or compromise of physiological functioning ca ....S. Z. Langer, "Denervation Supersensitivity", in: ''Principles of Receptor Research'' Volume 2 of the series Handbook of Psychopharmacology pp 245-280 It is a compensatory change. References {{reflist Peripheral nervous system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus (optics), focus on an object as its distance varies. In this, distances vary for individuals from the far point—the maximum distance from the eye for which a clear image of an object can be seen, to the near point—the minimum distance for a clear image. Accommodation usually acts like a reflex, including part of the accommodation-convergence reflex, but it can also be consciously controlled. The main ways animals may change focus are: * Changing the shape of the lens. * Changing the position of the lens relative to the retina. * Changing the axial length of the eyeball. * Changing the shape of the cornea. Focusing mechanisms Focusing the light scattered by objects in a three dimensional environment into a two dimensional collection of individual bright points of light requires the light to be bent. To get a good image of these points of light on a defined area re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Short Ciliary Nerves
The short ciliary nerves are nerves of the orbit around the eye. They are branches of the ciliary ganglion. They supply parasympathetic and sympathetic nerve fibers to the ciliary muscle, iris, and cornea. Damage to the short ciliary nerve may result in loss of the pupillary light reflex, or mydriasis. Structure The short ciliary nerves are branches of the ciliary ganglion. They arise from the forepart of the ganglion in two bundles connected with its superior and inferior angles. The lower bundle is the larger than the upper bundle. These split into between 6 and 10 filaments. They run forward with the ciliary arteries in a wavy course. One bundle is set above the optic nerve, while the other bundle is set below it. They are accompanied by the long ciliary nerves from the nasociliary. They pierce the sclera at the back part of the bulb of the eye, pass forward in delicate grooves on the inner surface of the sclera, and are distributed to the ciliary muscle, iris, and corne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edinger–Westphal Nucleus
The Edinger–Westphal nucleus also called the accessory or visceral oculomotor nerve, is one of the two nuclei of the oculomotor nerve (CN III) located in the midbrain. It receives afferents from both pretectal nuclei (which have in turn received afferents from the optic tract). It contains parasympathetic pre-ganglionic neuron cell bodies that synapse in the ciliary ganglion. It contributes the autonomic, parasympathetic component to the oculomotor nerve (CN III), ultimately providing innervation to the iris sphincter muscle and ciliary muscle to mediate the pupillary light reflex and accommodation, respectively. The Edinger–Westphal nucleus has two parts. The first is of preganglionic fibers (EWpg) that terminate in the ciliary ganglion. The second is of centrally projecting cells (EWcp) that project to a number of brainstem structures. Structure The Edinger–Westphal nucleus refers to the adjacent population of non-preganglionic neurons that do not project to the cilia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oculomotor Nerve
The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of the eye and that raise the eyelid. The nerve also contains fibers that innervate the intrinsic eye muscles that enable pupillary constriction and accommodation (ability to focus on near objects as in reading). The oculomotor nerve is derived from the basal plate of the embryonic midbrain. Cranial nerves IV and VI also participate in control of eye movement. Structure The oculomotor nerve originates from the third nerve nucleus at the level of the superior colliculus in the midbrain. The third nerve nucleus is located ventral to the cerebral aqueduct, on the pre-aqueductal grey matter. The fibers from the two third nerve nuclei located laterally on either side of the cerebral aqueduct then pass through the red nucleus. From the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
