By V. Uruk. University of Saint Mary. 2018.
Zigmond order 1 mg estrace visa breast cancer walk, RE cheap 1 mg estrace otc womens health 15 minute workouts, Schwarzschild, MA and Rittenhouse, AR (1989) Acute regulation of tyrosine hydroxylase by nerve activity and by neurotransmitters via phosphorylation. Edited by Roy Webster Copyright & 2001 John Wiley & Sons Ltd ISBN: Hardback 0-471-97819-1 Paperback 0-471-98586-4 Electronic 0-470-84657-7 9 5-H ydroxytryptam ine S. STANFORD INTRODUCTION The idoleamine, 5-hydroxytryptamine (5-HT), like the catecholamines, dopamine and noradrenaline, is found in both the periphery and the brain. This chapter will concentrate on the aspects of 5-HT transmission which have made the greatest advances in recent years, particularly those for which some important and interesting questions remain unanswered. Although this material will obviously focus on 5-HT in the brain, the neurochemical mechanisms that regulate 5-HT transmission, such as its synthesis and inactivation, will apply generally to 5-HT-containing cells in the periphery (e. All these processes, together with some well-known drugs that affect them, are summarised in Fig. DISTRIBUTION IN THE CNS As with the other monoamines, the distribution of 5-HT-releasing neurons in the brain was first characterised in the 1960s using the Falck±Hillarp histochemical technique whereby 5-HT is converted to a compound that is fluorescent under ultra-violet light. This showed that the cell bodies of 5-HT neurons aggregate around the midline of the upper brainstem, forming distinct clusters (or nuclei) (Fig. Since then, 5-HT neurons have been found in the noradrenergic locus coeruleus and the area postrema as well. Yet, despite this relatively restricted distribution of cell bodies, their processes project more or less throughout the whole neuraxis. For a detailed review of this topic, see Jacobs and Azmitia (1992) but an outline of key features is given here. The clusters of 5-HT cell bodies (the so-called Raphe nuclei) were originally perceived as forming nine separate nuclei (designated B1±B9) but current nomenclature has reclassified these to some extent so that, currently the nuclei incorporate cell bodies from more than one of those described originally (Table 9. Despite these changes, all these nuclei are still regarded as forming two major groups. This means that these neurons are well placed for serving a key role in regulation of motor activity, autonomic function and nociception. In addition, there are numerous interconnections between the different Neurotransmitters, Drugs and Brain Function. Webster &2001 John Wiley & Sons Ltd 188 NEUROTRANSMITTERS, DRUGS AND BRAIN FUNCTION 5-HYDROXYTRYPTAMINE 189 Figure 9. The most prominent of these is the median forebrain bundle which contains both myelinated and unmyelinated 5-HT fibres. Although extensive branching of the neuronal processes results in a considerable overlap in the terminal axonal fields of the different nuclei, there is evidence for some topographical organisation of the areas to which different nuclei project (Fig. For instance, whereas fibres emanating from the dorsal Raphe nucleus (DRN) are the major source of 5-HT terminals in the basal ganglia and cerebellum, neurons in the median Raphe nucleus (MRN) provide the major input to the hippocampus and septum. There is also some evidence for morphological differences between DRN and MRN neurons which could impinge on their function. Thus, the terminals of neurons from the DRN are relatively fine, unmyelinated, branch extensively and seem to make no specialised synaptic contacts, suggesting en passant release of 5-HT (type I). The existence of co-transmitters, especially substance P, thyrotropin releasing hormone (TRH) and enkephalin, gives further options for functional specialisation of different neurons but, as yet, the distribution of these peptides within different nuclei has provided no specific clues as to how this might occur. In any case, species differences in the distribution of co-transmitters is a confounding factor. In short, although the 5-HT system seems to have a rather non-specific influence on overall brain function, in terms of the brain areas to which these neurons project, there is clearly much to be learned about possible functional and spatial specialisations of neurons projecting from different nuclei. SYNTHESIS The first step in the synthesis of 5-HT is hydroxylation of the essential amino acid, tryptophan, by the enzyme tryptophan hydroxylase (Fig. This enzyme has several features in common with tyrosine hydroxylase, which converts tyrosine to l-DOPA in 5-HYDROXYTRYPTAMINE 191 Figure 9. The primary substrate for the pathway is the essential amino acid, tryptophan and its hydroxylation to 5-hydroxytryptophan is the rate- limiting step in the synthesis of 5-HT. The cytoplasmic enzyme, monoamine oxidase (MAOA), is ultimately responsible for the catabolism of 5-HT to 5-hydroxyindoleacetic acid the noradrenaline synthetic pathway. First, it has an absolute requirement for O2 and the reduced pterin co-factor, tetrahydrobiopterin. Second, hydroxylation of trypto- phan, like that of tyrosine, is the rate-limiting step for the whole pathway (reviewed by Boadle-Biber 1993) (see Chapter 8). However, unlike the synthesis of noradrenaline, the availability of the substrate, tryptophan, is a limiting factor in the synthesis of 5-HT. Indeed, the activated form of tryptophan hydroxylase has an extremely high Km for tryptophan (50 mM), which is much greater than the concentration of tryptophan in the brain (10±30 mM).
The use of salt restriction and diuretics would reduce the slight resistance to passive movement that is detectable in overall hydration state of his body and tend to reduce ab- a relaxed muscle cheap estrace 2 mg with mastercard menstruation kit, becomes greatly increased and demon- normal pressure within the labyrinthine system estrace 1 mg lowest price women's health magazine best body meal plan. Spastic tone is antimotion sickness drugs would interfere with the natural most evident in the flexor muscles of the arm and the ex- neural compensation that would, it is hoped, reduce the tensor muscles of the leg. The extensor movement of the first toe in response to Reference stroking the plantar aspect of the foot, termed Babinski Drachman DA. JAMA sign, is thought to occur because of modification of flexor 1998;280:2111–2118. The Cushing response (described by famous neurosurgeon flex when the plantar surface is stimulated. Harvey Cushing) consists of the development of hyperten- The neurophysiological details of how the deficit in sion, bradycardia, and apnea in patients with increased in- corticospinal input actually produces these commonly tracranial pressure most often a result of tumors or other le- encountered abnormalities in muscle tone and reflex sions, such as hemorrhage, that compress the brain. A current theory is pressure is transmitted downward to the brainstem and dis- that the disturbance of central control reduces the torts the medulla, where the centers for blood pressure, threshold of the stretch reflex but does not alter its gain. Correct interpre- References tation of these abnormalities in vital signs permits begin- Lance JW. The control of muscle tone, reflexes, and move- ning treatments that reduce intracranial pressure. Quantitative relations an artificial respirator, and then instituting hyperventilation between hypertonia and stretch reflex threshold in spastic to lower the blood PCO2 to produce cerebral vasoconstric- hemiparesis. Another autonomic reaction from the CNS that is uti- CASE STUDY FOR CHAPTER 6 lized daily in hospitals is the response of fetal heart rate Autonomic Dysfunction as a Result of CNS Disease to compression of the head during labor. During uterine A 30-year-old patient came to the hospital emergency contractions, the fetal head is temporarily compressed. Previously he the cranium are not yet fused, the pressure of the con- had experienced only mild, infrequent tension traction is transmitted to the brain. Because of the nism of cardiac slowing as cited for the Cushing re- intensity of this new headache, he is treated with in- sponse is presumed to cause the temporary bradycardia. Additional factors, such as umbilical cord com- consciousness declines to the point of responding only pression, may also produce patterns of slowing outside to painful stimuli. The central nervous system and cardiovascular the blood is thought to be a ruptured cerebral artery control in health and disease. Philadelphia: Lippincott-Raven, 1997 During the next 24 hours, the patient’s ECG begins to show abnormalities consisting of both tachycardia and changes in the configuration of the waves suggestive of CASE STUDY FOR CHAPTER 7 a heart attack. For the preceding 2 days, the patient’s wife had no- Questions ticed that he did not seem to make sense when he spoke. What is the explanation for the cardiac abnormalities in this She also indicated that he seemed a little disoriented situation? Describe two other scenarios in which there are prominent has no obvious motor or somatic sensory deficits. The consulting cardiologist reviewed the situation and man’s visual fields and notices a decreased awareness stated that the ECG abnormalities were all a result of sub- of stimuli presented to one visual field. What information from the case history gives the answers stimulate excessive activity of the sympathetic nervous to questions 1 and 2? The stroke involved the superior posterior temporal lobe en- norepinephrine from sympathetic nerve endings and epi- compassing Wernicke’s area and the occipital lobe encom- nephrine by the adrenal medulla. Language deficits indicate involvement of the left hemi- duce the same ECG abnormalities in experimental ani- sphere. The fluent but nonsensical speech indicates involve- mals as were found in this patient. The visual field deficit indicates a lease of norepinephrine and epinephrine stimulates the loss in the visual cortex. The lack of motor or somatic sen- cardiac conducting system and may also produce direct sory deficits excludes the posterior frontal and anterior pari- damage of the myocardium. The right visual field would be affected, because visual ters can be lifesaving.
A family history of breast cancer purchase estrace 2 mg with mastercard women's health clinic va boise, particularly under age 45 years buy cheap estrace 1 mg on line women's health center grand rapids mammogram, imparts increased risk to the patient. All suspicious masses should be biopsied, regardless of the mammogram interpretation. The diagnosis of cervical cancer is an important consideration in the evaluation of intravaginal bleeding. Pelvic sonography in the postmeno- pausal patient may be done to assess the thickness of the endometrium. Again, the patient’s history is often telling and may lead to a diagnosis of cancer when the appropriate evaluations are performed. The other major area of liability for this specialty is prenatal care and delivery. Prenatal diagnostic ultrasonographic evaluation of the fetus is an increasing area of litigation. It is essential that the respon- sible Ob/Gyn clarify for the patient what fetal anatomy can or cannot be seen and what diagnoses can or cannot be made. Limitations of equipment, the impact of fetal position and number, and maternal size should be emphasized. For example, only one-third of major fetal anatomic abnormalities are defined at second-trimester scans. Even when a consultant provides the interpretation of the study, the primary Ob/Gyn should review the implications of the findings with the patient and family. Additionally, genetic counseling is now so complex that only a certified counselor should do it. Fetal death imparts a responsibility on the part of the delivering phy- sician for documentation of the gross anatomy of the baby, the umbilical cord, and the placenta. Such descriptors are far more meaningful than those following examination by the pathologist hours to days later. The bulk of suits for wrongful fetal death arise when the death is unexplained, although up to 75% of fetal deaths can be under- stood after thorough gross, microscopic, and genetic analyses (6). The obstetric department should define a protocol to assess all fetal deaths. Much potential litigation can be prevented by the responsible Ob/Gyn discussing all findings with the patient and her family. This review should take place prior to discharge from the hospital and again at the postpartum visit. Under no circumstances should the patient be left with unanswered questions or concerns as these only drive attempts to get explanations from an attorney. Complications of induction of labor, although not very common, do occur and have associated risks to mother and, more commonly, baby. Informed consent should be obtained according to ACOG Practice Bulletin regarding induction of labor (7). Elements of the consent include the indication for the induction, the agents and methods of labor stimulation, the risks attendant to the use of these agents, meth- ods and alternatives (typically expectant management or Cesarean section [C-section]), and the associated risk for mother and baby. It is noteworthy that the bulletin states, “A physician capable of perform- ing a Cesarean delivery should be readily available. It is rec- ommended that all patients undergoing labor induction have electronic fetal heart rhythm and uterine contraction monitoring although its utility is problematic except in the high-risk pregnancy. Electronic fetal heart rate (FHR) monitoring is a classic example of a procedure becoming codified as the standard of care without proof of effectiveness. In fact, the prevalence of cerebral palsy has not been altered by this modality (8). The physician must be certain that he or she and the nurses are using the same terminology in describing the FHR tracing. For example, quantification of variability is subjective, and there is no such terminology as late variables—indeed variable decelerations are so named in part because the timing of the decelera- tion to the uterine contraction varies in its onset, including occurring late. Just as important, the physician should review the nurses’ notes with special attention to the terminology used, contact times, informa- tion given to the physician, and the physician’s responses.
Postganglionic Monocular field neurons in the ciliary ganglia behind the eyes cheap estrace 1 mg breast cancer kamikaze, in turn best 1mg estrace menstrual joke, stimulate Binocular field constrictor fibers in the iris. Contraction of the ciliary body during Macular field accommodationalso involves stimulation of the superior colliculi. Processing of Visual Information For visual information to have meaning, it must be associated with past experience and integrated with information from other Eyeball senses. Some of this higher processing occurs in the inferior tem- Lens poral lobes of the cerebral cortex. Experimental removal of these Retina areas from monkeys impairs their ability to remember visual tasks that they previously learned and hinders their ability to associate Topic Icons visual images with the significance of the objects viewed. Mon- Optic nerve keys with their inferior temporal lobes removed, for example, Topic icons highlight information of practical will fearlessly handle a snake. The symptoms produced by loss of the inferior temporal lobes are known asKlüver–Bucy syndrome. These commentaries In an attempt to reduce the symptoms of severe epilepsy, reinforce the importance of learning the preceding Optic chiasma surgeons at one time would cut the corpus callosum in some pa- tients. The five icon images and the topics they represent between the right and left cerebral hemispheres. The right cere- bral hemisphere of patients with suchsplit brainswould therefore, are: clinical information (stethoscope), aging Optic tract receive sensory information only from the left half of the external Superior world. The left hemisphere, similarly cut off from communication (hourglass), developmental information (embryo), Optic radiation colliculus with the right hemisphere, would receive sensory information only from the right half of the external world. In some situations, homeostasis (gear mechanism), and academic interest Lateral geniculate these patients would behave as if they had two separate minds. If the sensory image of an ob-ject, such as a key, is delivered only to the left hemisphere (by Visual cortex of object is presented to the right cerebral cortex, the person knows whatshowing it only to the right visual field), the object can be named. Experiments such as this suggest that (in right-handed people) the left hemisphere is needed for language Knowledge Check Creek and the right hemisphere is responsible for pattern recognition. Placed at the end of each major section, Knowledge Knowledge Check Check questions help you test your understanding of FIGURE 15. An overlapping of the visual field of each eye provides binoc-Visual fields of the eyes and neural pathways for 15. List the accessory structures of the eye that either cause the ular vision—the ability to perceive depth. Diagram the structure of the eye and label the following: sclera, cornea, choroid, retina, fovea centralis, iris, pupil, superior colliculi stimulate the extrinsic ocular muscles (see lens, and ciliary body. Smooth pursuit movementstrack moving objects and and explain the mechanism of light refraction. List the different layers of the retina and describe the path movements that occur while the eyes appear to be still. Con- saccadic movements are believed to be important in maintaining tinue tracing the path of a visual impulse to the cerebral visual acuity. The tectal system is also involved in the control of theintrin- sic ocular muscles—the smooth muscles of the iris and of the ciliary body. Shining a light into one eye stimulates the pupillary reflex in Klüver–Bucy syndrome: from Heinrich Klüver, German neurologist, 1897–1979 which both pupils constrict. Sesamoid bones events involved in the prenatal development of the profiled body The Axial Skeleton are specialized intramembranous bones that develop in tendons. EXPLANATION DEVELOPMENT OF THE SKULL Development of Bone The formation of the skull is a complex process that begins dur- Bone formation, orossification,begins at about the fourth week of well beyond the birth of the baby. Three aspects of the embry-ing the fourth week of embryonic development and continues embryonic development, but ossification centers cannot be read-ily observed until about the tenth week (exhibit I). Bone tissue onic skull are involved in this process: the chondrocranium, the derives from specialized migratory cells of mesoderm (see neurocranium, and the viscerocranium (exhibit II). Thedrocraniumis the portion of the skull that undergoes endochon-chon- fig.
May hear (or feel from usually have difﬁculty understanding than 90 vibrations) only very loud sounds purchase 1mg estrace visa menstruation pronunciation. Hearing loss may be congenital or The type and degree of hearing loss ex- acquired generic 2mg estrace fast delivery breast cancer fundraiser ideas. Congenital hearing loss is present perienced by individuals, regardless of the at birth. Hearing loss usually hearing loss are genetic transmission (inheri- involves more than a reduction in the ted hearing loss), caused by the mother’s loudness of sound. Some hearing losses prenatal ingestion of drugs that are harm- also result in a distortion of sound so that ful to the developing auditory system of words may be heard but are difﬁcult to the fetus or prenatal exposure to in- understand or are garbled. The degree, pro- may develop recruitment, a symptom gression, and age of onset of inherited characterized by an abnormally rapid in- hearing loss vary widely, depending on crease in the perception of loudness with the speciﬁc condition or syndrome. Individuals some instances, genetics may not cause with recruitment have a narrow range deafness per se but rather predispose in- between a level of sound loud enough to dividuals to hearing loss induced by be understood and a level of sound that noise, drugs, or infection (Steel, 2000). Unexpected many instances hearing loss is multifacto- sounds may startle individuals with re- rial, caused by both genetic and environ- cruitment and distract them from inter- mental factors (Williams, 2000). There- Acquired hearing loss occurs after birth or fore, increasing the loudness of sound later in life. There are a number of causes does not correct the hearing problem and of acquired hearing loss. Noise-induced hearing loss is a com- Conditions of the Outer Ear mon but preventable type of acquired hearing loss. Avoiding loud noises or wear- Conditions of the outer ear can con- ing ear protectors when exposed to loud tribute to hearing loss when there is an noise could drastically reduce the inci- obstruction that disrupts the mechanical dence of noise-induced hearing loss. Although conditions of injury or disease, such as from traumatic the outer ear may not have a major impact brain injury or from multiple sclerosis on hearing or may be correctable, they affecting the auditory pathway. Presby- may also be disﬁguring, causing cosmetic cusis (hearing loss associated with aging) concerns. The extent to the outer ear can result from congenital which degeneration of portions of the au- conditions or from trauma. Other condi- ditory system is due to the aging process tions of the outer ear that may impede Hearing Loss and Deafness 149 hearing are buildup of earwax (cerumen), Because of the proximity of the mastoid foreign bodies in the ears, or growths (e. Com- as it once was because of the earlier detec- plete occlusion, however, generally results tion of otitis media and treatment with in a low to moderate conductive loss. Con- antibiotics; however, chronic mastoiditis ditions of the outer ear that cause tempo- and associated complications can result if rary conductive hearing impairments can previous ear infections are left untreated. Otosclerosis Conditions of the Middle Ear Otosclerosis is a hardening of the ossi- cles (incus, stapes, and malleus of the mid- Conditions of the middle ear may cause dle ear), which transmit sound impulses temporary or permanent hearing loss. Early symptoms may in- clude trouble hearing on the telephone Perforated Tympanic Membrane but not in crowds. It causes conduc- A thickened or perforated tympanic mem- tive hearing loss because hardening of the brane (ruptured eardrum) may or may not ossicles reduces the efﬁciency of the trans- impair hearing. Some individuals may also have vestibular symptoms such as ver- Otitis Media tigo (dizziness) or impaired equilibrium. Individuals with otosclerosis often hear Otitis media (inﬂammation and ﬂuid ampliﬁed speech well and without distor- buildup in the middle ear) can cause con- tions; consequently, they are usually good ductive hearing losses because of collec- candidates for hearing aids. Hearing can tion of ﬂuid in the middle ear or because also often be restored or improved with of damage to the tympanic membrane (ear- surgical intervention; however, surgery drum) as a result of infection or rupture. When de- Usually, with appropriate treatment, per- termining if surgery is appropriate, indi- manent hearing loss will not result. If not viduals’ lifestyle and occupation are con- treated promptly, however, otitis media sidered. Since surgery may affect vestibu- can lead to mastoiditis (Hendley, 2002). If individuals’ hob- Mastoiditis is an infection of the mas- bies or occupations expose them to large toid cells within the mastoid process locat- and rapid changes in barometric pressure, ed in the temporal bone of the skull. A number of therapies, including group Conditions of the Inner Ear cognitive therapy, have been used to help people cope with tinnitus. Adjustment to Many conditions of the inner ear cause tinnitus does not appear to be related to permanent hearing loss. Labyrinthitis Meniere’s Disease Labyrinthitis (inflammation of the labyrinth of the inner ear) may be acute Meniere’s disease is a disorder of the without resulting in permanent hearing inner ear that encompasses the triad of loss. Labyrinthitis may occur as a compli- recurrent severe vertigo, sensorineural hear- cation of otitis media, inﬂuenza, or upper ing loss, and tinnitus (noise or ringing in respiratory infections.