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STUDENT DIGITAL NEWSLETTER ALAGAPPA INSTITUTIONS |
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Peter E. Andersen, MD
The facial nerve and its branches supply the orbicularis oculi muscle allergy forecast lynchburg va discount deltasone 40mg visa, which causes closure of the eyelids best allergy medicine in japan discount deltasone 40 mg fast delivery. The visual impulses follow the optic nerves allergy symptoms nhs buy deltasone 5mg free shipping, optic chiasma allergy shots for juniper proven deltasone 40 mg, and optic tracts to the superior colliculi. Here, the impulses are relayed to the tectospinal and tectobulbar (tectonuclear) tracts and to the neurons of the anterior gray columns of the spinal cord and cranial motor nuclei. The white rami communicantes of these segments pass to the sympathetic trunk, and the preganglionic fibers ascend to the superior cervical sympathetic ganglion. The postganglionic fibers pass through the internal carotid plexus and the long ciliary nerves to the dilator pupillae muscle of the iris. The nucleus consists of groups of nerve cells that supply all the extrinsic muscles of the eye except the superior oblique and the lateral rectus. The outgoing nerve fibers pass anteriorly through the red nucleus and emerge on the anterior surface of the midbrain in the interpeduncular fossa. It also receives fibers from the medial longitudinal fasciculus, by which it is connected to the nuclei of the fourth, sixth, and eighth cranial nerves. The accessory parasympathetic nucleus (Edinger-Westphal nucleus) is situated posterior to the main oculomotor nucleus. The axons of the nerve cells, which are preganglionic, accompany the other oculomotor fibers to the orbit. Here, they synapse in the ciliary ganglion, and postganglionic fibers pass through the short ciliary nerves to the constrictor pupillae of the iris and the ciliary muscles. The accessory parasympathetic nucleus receives corticonuclear fibers for the accommodation reflex and fibers from the pretectal nucleus for the direct and consensual light reflexes. It passes forward between the posterior cerebral and the superior cerebellar arteries. It then continues into the middle cranial fossa in the lateral wall of the cavernous sinus. Here, it divides into a superior and an inferior ramus, which enter the orbital cavity through the superior orbital fissure. The oculomotor nerve supplies the following extrinsic muscles of the eye: the levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique. It also supplies, through its branch to the ciliary ganglion and the short ciliary nerves, parasympathetic nerve fibers to the following intrinsic muscles: the constrictor pupillae of the iris and ciliary muscles. It lies inferior to the oculomotor nucleus at the level of the inferior colliculus. The nerve fibers, after leaving the nucleus, pass posteriorly around the central gray matter to reach the posterior surface of the midbrain. It receives the tectobulbar fibers, which connect it to the visual cortex through the superior colliculus. Course of the Trochlear Nerve the trochlear nerve, the most slender of the cranial nerves and the only one to leave the posterior surface of the brainstem, emerges from the midbrain and immediately decussates with the nerve of the opposite side. Trigeminal Nerve (Cranial Nerve V) the trigeminal nerve is the largest cranial nerve and contains both sensory and motor fibers. Trigeminal Nerve Nuclei the trigeminal nerve has four nuclei: (1) the main sensory nucleus, (2) the spinal nucleus, (3) the mesencephalic nucleus, and (4) the motor nucleus. Spinal Nucleus the spinal nucleus is continuous superiorly with the main sensory nucleus in the pons and extends inferiorly through the whole length of the medulla oblongata and into the upper part of the spinal cord as far as the second cervical segment. About half the fibers divide into ascending and descending branches when they enter the pons; the remainder ascend or descend without division. The ascending branches terminate in the main sensory nucleus, and the descending branches terminate in the spinal nucleus. The sensations of touch and pressure are conveyed by nerve fibers that terminate in the main sensory nucleus. Proprioceptive impulses from the muscles of mastication and from the facial and extraocular muscles are carried by fibers in the sensory root of the trigeminal nerve that have bypassed the semilunar or trigeminal ganglion. It also receives fibers from the reticular formation, the red nucleus, the tectum, and the medial longitudinal fasciculus. In addition, it receives fibers from the mesencephalic nucleus, thereby forming a monosynaptic reflex arc. The large sensory root now expands to form the crescent-shaped trigeminal ganglion, which lies within a pouch of dura mater called the trigeminal or P. The maxillary nerve (V2) also contains only sensory fibers and leaves the skull through the foramen rotundum. Abducent Nerve Nucleus the small motor nucleus is situated beneath the floor of the upper part of the fourth ventricle, close to the midline and beneath the colliculus facialis. It receives the tectobulbar tract from the superior colliculus, by which the visual cortex is connected to the nucleus. It passes forward through the cavernous sinus, lying below and lateral to the internal carotid artery. The abducent nerve is entirely a motor nerve and supplies the lateral rectus muscle and, therefore, is responsible for turning the eye laterally. Note that the skin over the angle of the jaw is supplied by the great auricular nerve (C2 and C3) and not by branches of the trigeminal nerve. The part of the nucleus that supplies the muscles of the upper part of the face receives corticonuclear fibers from both cerebral hemispheres. However, another involuntary pathway exists; it is separate and controls mimetic or emotional changes in facial expression. Parasympathetic Nuclei Parasympathetic nuclei lie posterolateral to the main motor nucleus. The superior salivatory nucleus receives afferent fibers from the hypothalamus through the descending autonomic pathways. Sensations of taste travel through the peripheral axons of nerve cells situated in the geniculate ganglion on the seventh cranial nerve. Course of the Facial Nerve the facial nerve consists of a motor and a sensory root. They then pass around the nucleus beneath the colliculus facialis in the floor of the fourth ventricle and, finally, pass anteriorly to emerge from the brainstem. The sensory root (nervus intermedius) is formed of the central processes of the unipolar cells of the geniculate ganglion. At the bottom of the meatus, the nerve enters the facial canal and runs laterally through the inner ear. On reaching the medial wall of the tympanic cavity, the nerve expands to form the sensory geniculate ganglion. B: Branches of the facial nerve within the petrous part of the temporal bone; the taste fibers are shown in black. The superior salivatory nucleus supplies the submandibular and sublingual salivary glands and the nasal and palatine glands. The sensory nucleus receives taste fibers from the anterior two-thirds of the tongue, the floor of the mouth, and the palate. Vestibular Nerve the vestibular nerve conducts nerve impulses from the utricle and saccule that provide information concerning the position of the head; the nerve also conducts impulses from the semicircular canals that provide information concerning movements of the head. When they enter the vestibular nuclear complex, the fibers divide into short ascending and long descending fibers; a small number of fibers pass directly to the cerebellum through the inferior cerebellar peduncle, bypassing the vestibular nuclei. Four nuclei may be recognized: (1) the lateral vestibular nucleus, (2) the superior vestibular nucleus, (3) the medial vestibular nucleus, and (4) the inferior vestibular nucleus. Efferent fibers also descend uncrossed to the spinal cord from the lateral vestibular nucleus and form the vestibulospinal tract. Ascending fibers also pass upward from the vestibular nuclei to the cerebral cortex, to the vestibular area in the postcentral gyrus just above the lateral fissure. The cerebral cortex probably serves to orient the individual consciously in space. The fibers of the cochlear nerve are the central processes of nerve cells located in the spiral ganglion of the cochlea. On entering the pons, the nerve fibers divide, with one branch entering the posterior cochlear nucleus and the other branch entering the anterior cochlear nucleus. Cochlear Nuclei the anterior and posterior cochlear nuclei are situated on the surface of the inferior cerebellar peduncle. The cochlear nuclei send axons (second-order neuron fibers) that run medially through the pons to end in the trapezoid body and the olivary nucleus. Here, they are relayed in the posterior nucleus of the trapezoid body and the superior olivary nucleus on the same or the opposite side. The axons now ascend through the posterior part of the pons and midbrain and form a tract known as the lateral lemniscus.
Significant advancements in other specialties allergy medicine in 3rd trimester purchase 20mg deltasone visa, particularly neurosurgery allergy treatment machine buy deltasone 20mg otc, have prolonged life and unmasked the importance of maintaining normal renal function and a healthy bladder allergy on face deltasone 5 mg low price. Over 90% of children at birth have a normal upper urinary tract (kidney and ureter) allergy symptoms with body aches cheap 40mg deltasone overnight delivery. Historically, we know that if left unattended, 50% of those children will suffer upper urinary tract damage due to lower urinary tract (bladder and urethra) hostility. As the child begins to approach school age, greater interest is directed toward gaining urinary continence. Each of these urologic management milestones builds upon the last, potentially affecting their status in a positive or negative fashion. Two general philosophies prevail: a proactive approach that attempts to identify children at risk for upper urinary tract deterioration and treat them before a problem occurs; and a reactive approach that follows a child closely and begins management at the first sign of any adverse change. This is done in an attempt to prevent adverse upper urinary tract changes and preserve normal renal function, thus limiting exposure to possible irreversible upper tract deterioration. Institutions favoring a reactive approach rely on close evaluation of the upper urinary tract, renal function, and documentation of urinary infections. It is felt that adverse upper urinary tract changes can be detected early with minimally invasive assessment using ultrasonography. Adverse changes are assumed to be reversed with medical, pharmacologic, and operative management. Treating children reactively "as needed" allows for precise selective management limiting the stress and potential side effects of invasive procedures, medications, catheterization, and surgery. The importance for maintaining normal renal function within this guideline cannot be overstated. It is also appreciated that while creatinine is a good screening tool of renal function, it is limited in the non-ambulatory child and adult with Spina Bifida with low muscle mass and thus provides a false sense of normality. This guideline merges aspects of proactive and reactive philosophies based on a best practice methodology. Providing a strong foundation for pediatric care directly impacts the lifetime goals related to continence, self-management, and renal health. Maximize renal outcome while minimizing expense of studies, keeping watch over the timing and frequency of studies such as urodynamic testing, upper tract imaging, and lab studies. How do you define a symptomatic urinary tract infection and what is its long-term sequela Can diagnostic studies of the lower urinary tract (urodynamic) or upper urinary tract (ultrasonography) predict and prevent an adverse change in kidney function How can providers account for neurologic bladder changes due to growth and/or tethering Obtain renal/bladder ultrasound every six months when the child is under the age of two. Obtain a serum creatinine test if there is a change in imaging of the upper urinary tract. Introduce urinary continence and discuss interest in beginning the program and options at each visit. What is the best way to measure renal function in the child that is non-ambulatory What social, environmental, and economic limitations or hurdles are encountered when working to achieve urinary continence Is the definition of continence congruent with the perspective of the patient, family, and physician Obtain a serum B12 level test every year beginning two years after urinary reconstruction. Discuss a urinary continence program and interest in beginning the program and options at each visit. How is a normal upper urinary tract affected by a shift in responsibility to self-care If reconstructive continent bladder surgery was undertaken, would you do it again If the child has low muscle mass, consider an alternative measure of renal function. Obtain serum chemistries including B12 yearly on any child who has had urinary reconstruction. Transition urologic care to self-management, if doing so is developmentally appropriate for the child. Transition bowel program to self-management, if doing so is developmentally appropriate for the child. If the adult has low muscle mass, consider an alternative measure of renal function. Obtain serum chemistries including B12 on anyone who has had urinary reconstruction. Evaluate patterns of continence/incontinence and address issues collaboratively with the individual and family. Include assessment of amount (volume) of incontinence as the amount in adults may be more bothersome than frequency. However, it is not known what the best assessment is in the population with Spina Bifida. How is creatinine influenced by height, weight and mobility status of a patient with Spina Bifida Is cystatin C a more accurate indicator of renal function in the population with Spina Bifida What degree of renal dysfunction has occurred by the time changes are noted on imaging. Continence: Continence of the bowel and bladder plays an important role in socialization. Is the perception of continence from the perspective of the medical care provider and patient and family congruent What are the long-term challenges of patients who have undergone surgical intervention Would patients who have chosen surgery as a management option, make the same decision if they had the opportunity Management of the obstructed urinary tract associated with neurogenic bladder dysfunction. Long-term urological response of neonates with myelodysplasia treated proactively with intermittent catheterization and anticholinergic therapy. Preservation of renal function in children with myelomeningocele managed with basic newborn evaluation and close followup. Serum creatinine is a poor marker of glomerular filtration rate in patients with spina bifida. Design and methodological considerations of the centers for disease control and prevention urologic and renal protocol for the newborn and young child with spina bifida. Variation in definitions of urinary tract infections in spina bifida patients: a systematic review. Vitamin B12 malabsorption following bladder reconstruction or diversion with bowel segments. Long-term assessment of serum vitamin B12 concentrations in patients with various types of orthotopic intestinal neobladder. Psychosocial factors in teenagers and young adults with myelomeningocele and clean intermittent catheterization. Long-term complications following bladder augmentations in patients with spina bifida: bladder calculi, perforation of the augmented bladder and upper tract deterioration. Current status of urinary biomarkers for detection and surveillance of bladder cancer. Quantity, not frequency, predicts bother with urinary incontinence and its 169 impact on quality of life in adults with spina bifida. Estimation of Renal Function in Children and Adolescents with Spinal Dysraphism, J of Urology, 179:2407-2409, 2008 2. Postpubertal urodynamic and upper urinary tract changes in children with conservatively treated myelomeningocele. Hospitalization for urinary tract infections and the quality of preventive health care received by people with Spina Bifida.
Diagram shows the interactions of the ions with water allergy testing cpt code deltasone 40 mg mastercard, the membrane lipid bilayer allergy symptoms neck pain purchase deltasone 40 mg online, and the ion channels allergy shots vomiting buy discount deltasone 10 mg on line. Structure of the Neuron 47 be due to the inability to get the sodium channels open allergy forecast harrisburg pa cheap 5 mg deltasone free shipping. During the relative refractory period, when a very strong stimulus can produce an action potential, presumably the sodium channels are opened. The Nerve Cell Processes the processes of a nerve cell, often called neurites, may be divided into dendrites and an axon. Later, they are reduced in number and size in response to altered functional demand from afferent axons. There is evidence that dendrites remain plastic throughout life and elongate and branch or contract in response to afferent activity. It arises from a small conical elevation on the cell body, devoid of Nissl granules, called the axon hillock. Axons usually do not branch close to the cell body; collateral branches may occur along their length. Some Mitochondria Nerve cell body Dendrite Dendrite A Neuropil B Microtubules and microfilament Axons synapsing son dendrite Figure 2-19 A: Light photomicrograph of a motor neuron in the anterior gray column of the spinal cord showing the nerve cell body,two dendrites,and the surrounding neuropil. The initial segment of the axon is the first 50 to 100 m after it leaves the axon hillock of the nerve cell body. The axons of sensory posterior root ganglion cells are an exception; here, the long neurite, which is indistinguishable from an axon, carries the impulse toward the cell body. Fast anterograde transport of 100 to 400 mm per day refers to the transport of proteins and transmitter substances or their precursors. Axon hillock Initial segment of axon Microtubules Figure 2-20 Electron micrograph of a longitudinal section of a neuron from the cerebral cortex showing the detailed structure of the region of the axon hillock and the initial segment of the axon. Note the absence of Nissl substance (rough endoplasmic reticulum) in the axon hillock and the presence of numerous microtubules in the axoplasm. The definition has come to include the site at which a neuron comes into close proximity with a skeletal muscle cell and functional communication occurs. For example, activated growth factor receptors can be carried along the axon to their site of action in the nucleus. Pinocytotic vesicles arising at the axon terminals can be quickly returned to the cell body. Where two neurons come into close proximity and functional interneuronal communication occurs, the site of such communication is referred to as a synapse2. Most neurons may make synaptic connections to a 1,000 or more other neurons and may receive up to 10,000 connections from other neurons. Communication at a synapse,under physiologic conditions, takes place in one direction only. The most common type is that which occurs between an axon of one neuron and the dendrite or cell body of the second neuron. As the axon approaches the synapse, it may have a terminal expansion (bouton terminal),or it may have a series of expansions (bouton de passage), each of which makes synaptic contact. The manner in which an axon terminates varies considerably in different parts of the nervous system. In the same way,a single neuron may have synaptic junctions with axons of many different neurons. The arrangement of these synapses will determine the means by which a neuron can be stimulated or inhibited. Chemical Synapses Ultrastructure of Chemical Synapses On examination with an electron microscope, synapses are seen to be areas of structural specialization. On the presynaptic side,the dense cytoplasm is broken up into groups; on the postsynaptic side, the density often extends into a subsynaptic web. Presynaptic vesicles, mitochondria, and occasional lysosomes are present in the cytoplasm close to the presynaptic membrane. Structure of the Neuron 51 Axons near termination Presynaptic vesicles Dendrite Terminal expansion of axon Mitochondria Synaptic sites Microtubules interspersed among microfilaments Figure 2-23 High-power electron micrograph of axodendritic synapses showing the thickening of the cell membranes at the synaptic sites,presynaptic vesicles,and the presence of mitochondria within the axons near their termination. When synapses are first formed in the embryo, they are recognized as small zones of density separated by a synaptic cleft. This plasticity of synapses may be of great importance in the process of learning and in the development and maintenance of memory. Action of Neurotransmitters Neurotransmitters at Chemical Synapses the presynaptic vesicles and the mitochondria play a key role in the release of neurotransmitter substances at synapses. Most neurons produce and release only one principal transmitter at all their nerve endings. For example, acetylcholine is widely used as a transmitter by different neurons All neurotransmitters are released from their nerve endings by the arrival of the nerve impulse (action potential). The neurotransmitters are then ejected into the extracellular fluid in the synaptic cleft. There they achieve their objective by raising or lowering the resting potential of the postsynaptic membrane for a brief period of time. These receptors have a longer latent period, and the duration of the response may last several minutes or longer. Acetylcholine (muscarinic), serotonin,histamine,neuropeptides,and adenosine are good examples of this type of transmitter,which is often referred to as a neuromodulator (see next section). If, on the other hand, the overall effect is one of hyperpolarization,the neuron will be inhibited and no nerve impulse will arise. Distribution and Fate of Neurotransmitters Take-up process B Figure 2-24 Release of neurotransmitters. The distribution of the neurotransmitters varies in different parts of the nervous system. Acetylcholine, for example, is found at the neuromuscular junction,in autonomic ganglia, and at parasympathetic nerve endings. In the central nervous system, the motor neuron collaterals to the Renshaw cells are cholinergic. In the hippocampus, the ascending reticular pathways, and the afferent fibers for the visual and auditory systems,the neurotransmitters are also cholinergic. In the central nervous system, it is found in high concentration in the hypothalamus. Astrocytes 53 concentration in different parts of the central nervous system, such as in the basal nuclei (ganglia). However, with the catecholamines, the effect is limited by the return of the transmitter to the presynaptic nerve ending. Protoplasmic astrocytes are found mainly in the gray matter, where their processes pass between the nerve cell bodies. The cytoplasm of these cells contains fewer filaments than that of the fibrous astrocyte. Many of the processes of astrocytes end in expansions on blood vessels (perivascular feet),where they form an almost complete covering on the external surface of capillaries. Neuromodulators can coexist with the principal neurotransmitter at a single synapse. Whereas on release into the synaptic cleft the principal neurotransmitters have a rapid, brief effect on the postsynaptic membrane, the neuromodulators on release into the cleft do not have a direct effect on the postsynaptic membrane. The neuromodulators act through a second messenger system, usually through a molecular transducer, such as a G-protein, and alter the response of the receptor to the neurotransmitter. Such an arrangement can lead to a wide variety of responses,depending on the input from the afferent neurons. Electrical Synapses Electrical synapses are gap junctions containing channels that extend from the cytoplasm of the presynaptic neuron to that of the postsynaptic neuron: They are rare in the human central nervous system. Electrical synapses also have the advantage that they are bidirectional; chemical synapses are not. Functions of Astrocytes Astrocytes, with their branching processes, form a supporting framework for the nerve cells and nerve fibers. They may even form barriers for the spread of neurotransmitter substances released at synapses.
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