By F. Sinikar. Cardinal Stritch University.
This condition is tested clinically by distending an colon buy colospa 135mg otc, because the proximal colon may become grossly intrarectal balloon proven 135mg colospa. The healthy subject will perceive the enlarged with impacted feces generic colospa 135mg, or congenital agan- distension with an instilled volume of 15 mL or less discount colospa 135mg with visa, glionosis, because the ganglia of the ENS fail to develop whereas the sensory-deprived patient either will not report in the terminal region of the large intestine. Mutations in any sensation at all or will require much larger volumes RET or endothelin genes account for the disease in some before becoming aware of the distension. Incompetence of the internal anal sphincter is usually Enteric neurons may be absent in the rectosigmoid re- related to a surgical or mechanical factor or perianal dis- gion only, in the descending colon, or in the entire colon. Disorders of the The aganglionic region appears constricted as a result of neuromuscular mechanisms of the external sphincter and continuous contractile activity of the circular muscle, pelvic floor muscles may also result from surgical or me- whereas the normally innervated intestine proximal to the chanical trauma, such as during childbirth. Physiological deficiencies of the skeletal motor mech- The constricted terminal segment of the large intestine anisms can be a significant factor in the common occur- in Hirschsprung’s disease presents a functional obstruc- rence of incontinence in older adults. Constriction ing tone of the internal anal sphincter does not seem to and narrowing of the lumen of the segment reflects un- decrease with age, the strength of contraction of the ex- controlled myogenic contractile activity in the absence of ternal anal sphincter does weaken. Moreover, the stri- inhibitory motor neurons ated muscles of the external anal sphincter and pelvic Incontinence is an inappropriate leakage of feces and floor lose contractile strength with age. This condition flatus to a degree that it disables the patient by disrupting occurs in parallel with a deterioration of nervous func- routine daily activities. As discussed earlier, the mecha- tion, reflected by decreased conduction velocity in fibers nisms for maintaining continence involve the coordinated of the pelvic nerves. Clinical examination with intra-anal interactions of several different components. Conse- manometry reveals a decreased ability of the patient quently, sensory malfunction, incompetence of the inter- with disordered voluntary muscle function to increase in- nal anal sphincter, or disorders of neuromuscular mecha- tra-anal pressure when asked to “squeeze” the intra-anal nisms of the external sphincter and pelvic floor muscles catheter. This oc- Control by Inhibitory Motor Neurons of the Length of In- curs coincidently with control of contractile strength. Con- testine Occupied by a Contraction and the Direction of tractions can only occur in segments where ongoing inhi- Propagation of Contractions. The state of activity of in- bition has been inactivated, while it is prevented in hibitory motor neurons determines the length of a con- adjacent segments where the inhibitory innervation is ac- CLINICAL FOCUS BOX 26. As a re- Failure of peristalsis in the esophageal body or failure of the sult, the ingested material does not enter the stomach and lower esophageal sphincter to relax will result in dysphagia accumulates in the body of the esophagus. Some people show abnormally megaesophagus, in which distension and gross enlarge- high pressure waves as peristalsis propagates past the ment of the esophagus are evident. This condition, cases of achalasia, peristalsis does not occur in response called nutcracker esophagus, is sometimes associated to a swallow. Achalasia is a disorder of inhibitory motor neurons in In diffuse spasm, organized propagation of the peri- the lower esophageal sphincter. The number of neurons staltic behavioral complex fails to occur after a swallow. In- in the lower esophageal sphincter is reduced, and the lev- stead, the act of swallowing results in simultaneous con- els of the inhibitory neurotransmitter VIP and the enzyme tractions all along the smooth muscle esophagus. This degenerative disease manometric tracings, this response is observed as a syn- results in a loss of the inhibitory mechanisms for relaxing chronous rise in intraluminal pressure at each of the the sphincter with appropriate timing for a successful recording sensors. Myogenic contraction occurs in segments of intestine where inhibitory motor neurons are inactive. Sequential inactivation in the oral direction permits logical ileus occurs in segments of intestine where the inhibitory oral propagation of contractions. The oral and aboral boundaries of a contracted seg- vomiting, the integrative microcircuits of the ENS inacti- ment reflect the transition zone from inactive to active in- vate inhibitory motor neurons in a reverse sequence, allow- hibitory motor neurons. This is the mechanism by which ing small intestinal propulsion to travel in the oral direction the ENS generates short contractile segments during the and propel the contents toward the stomach (see Clinical digestive (mixing) pattern of small intestinal motility and Focus Box 26. Transiently Activated for Timed Opening As a result of the functional syncytial properties of the and the Passage of Luminal Contents musculature, inhibitory motor neurons are necessary for control of the direction in which contractions travel along The circular muscle of sphincters remains tonically con- the intestine. The directional sequence in which inhibitory tracted to occlude the lumen and prevent the passage of motor neurons are inactivated determines whether contrac- contents between adjacent compartments, such as between tions propagate in the oral or aboral direction (Fig. Inhibitory motor neurons are nor- Normally, the neurons are inactivated sequentially in the mally inactive in the sphincters and are switched on with aboral direction, resulting in contractile activity that prop- timing appropriate to coordinate the opening of the sphinc- agates and moves the intraluminal contents distally. During ter with physiological events in adjacent regions CLINICAL FOCUS BOX 26.
They must learn to deal with disability in order to avoid potential the uncertainty of whether and when rejection order 135 mg colospa mastercard. No matter how lepsy may be fearful of observing a seizure Conditions Affecting the Brain 65 or may be concerned that the disorder is out a disability because of anticipated hereditary order colospa 135 mg amex. Because of anxiety and misin- rejection due to real or perceived public formation generic 135mg colospa overnight delivery, they may be unwilling to learn attitudes cheap 135 mg colospa amex. Inability to drive can limit social Sexual activity, in most cases, need not interaction, educational experiences, and be affected by epilepsy (Frazer & Gumnit, employment opportunities. Although some medications used stances, individuals with epilepsy can to treat seizures may have some effect on drive without significant risk of accident libido, most do not. Psychological issues if their seizures are controlled with med- of low self-esteem or poorly developed ication. Individuals may be reluctant to were restricted from driving motor vehi- form intimate relationships because of the cles because of concerns for public safety fear of having a seizure. Although today be necessary to help them overcome this most states permit individuals with epilep- fear so that appropriate intimate relation- sy to obtain driver’s licenses, the length of ships can be established. State laws do not always take into ing a seizure, there are no outward signs account individual differences; some make of disability. Although considerable effort blanket rules that apply to all individuals has been devoted to educate the public with epilepsy regardless of their personal about the condition, misinformation and circumstances. In some cultures, historical with epilepsy should always consult their misconceptions about epilepsy have physician about alcohol consumption, es- linked it to demonic possession and insan- pecially in regard to taking alcohol when ity. In other instances people with epilep- they are also taking anticonvulsant med- sy were not permitted to participate in ication; however, each individual situation various events because of their diagnosis. Attitudes have changed in recent years as Sports activities are also an important the result of public education programs, means of socializing as well as helping in- improved placement of individuals with dividuals build self-confidence and self- epilepsy into the world of work, and in- esteem. In some situations, restrictions on creased ability to control seizures. In many participation in various activities are placed instances, however, individuals with on individuals with epilepsy even though epilepsy may still experience unjust re- no basis for limiting the activities exists. The stigma be precipitated by fatigue or other sports- and shame associated with epilepsy may related circumstances, others may have a cause individuals and/or their family to reduced incidence of seizures with exercise. Indi- Consequently, authorities should consider viduals may try to pass as someone with- the individual’s specific circumstances 66 CHAPTER 2 CONDITIONS OF THE NERVOUS SYSTEM: PART I rather than issuing blanket restrictions; reducing stress are other self-management each case should be considered individu- issues individuals with epilepsy must ally. The stress, uncertainty, restric- cific activities that present a hazard should tions, isolation, and difficulty with em- a seizure that involves loss of consciousness ployment all require adjustment and take place. For instance, individuals with coping skills if individuals are to achieve epilepsy should not swim alone. In most Most individuals with epilepsy have the instances applying common sense enables same range of IQ as the general popu- individuals to participate in activities lation, unless other conditions that affect while also avoiding potential hazards. How- Even when seizures are relatively well ever, individuals with epilepsy experience controlled, individuals may still fear hav- both unemployment and underemploy- ing the “occasional” seizure and the phy- ment (Bishop, 2004; Fisher, 2000). Many sical and social consequences it may problems in the workplace for individuals bring. In addition to the embarrassment with epilepsy continue to be related to of having a seizure in public, individuals misperceptions and stigma rather than may also fear injury. Although some in- seizure while performing routine tasks, dividuals with epilepsy, especially epilep- such as setting clothes on fire from gas sy associated with head trauma, may have stoves or falling in the bathtub, can occur. Con- in establishing commonsense safety pre- sequently, special consideration must be cautions for activities of daily living. Family, friends, and coworkers should also Epilepsy is a chronic condition that be informed about appropriate procedures requires a continuous relationship with if a seizure occurs. Medication is, of Despite control of seizures, individuals course, a major part of treatment and may still feel the weight of their restric- requires close medical supervision. For control seizures, and the medications instance, in most states individuals are themselves may have associated side required to report that they have epilep- effects. Individuals must be diligent in tak- sy when applying for a driver’s license.
Woolf 135mg colospa amex, NJ (1991) Cholinergic systems in mammalian brain and spinal cord generic 135mg colospa visa. Zinnerman purchase colospa 135 mg, H buy colospa 135 mg online, Volknandt, W, Wittich, B and Hausinger, A (1993) Synaptic vesicle lifecycle and synaptic turnover. 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 7 opam ine (D ) R. WEBSTER Dopamine (3:4 dihydroxyphenylethylamine), like noradrenaline and adrenaline, is a catecholamine and in addition to its independent neurotransmitter role in the CNS it is a precursor to noradrenaline (NA) in all central and peripheral noradrenegic neurons. PATHWAYS It became possible to visualise neurons which contained catecholamines when it was discovered that these amines reacted with formaldehyde vapour (later replaced by glyoxylic acid) to produce isoquinoline condensation products which emitted a bright- green fluorescence when visualised under ultra-violet light. This was distinguishable from the yellow fluorescence of 5-HT and could be separated from that for NA by appropriate pharmacological manipulations or adjustments to the microscopic techniques. Using this procedure, which is known as the Falk±Hillarp technique, Dahlstrom and Fuxe (1964) located and numbered nuclei in the hindbrain (pons medulla) in which either DA (A8±A12) or NA (1±7) was concentrated. Most of the DA cell bodies (about 400 000) in the human brain are found in the A9 nucleus which forms the zona compacta (dorsal part) of the substantia nigra (SN), although a few cell bodies are found in the more ventral zona reticulata and in the zona lateralis as well (Fig. A8 is lateral, caudal and somewhat dorsal to A9 and A10 whereas A10 is ventral to A9. Axons from A9 form the major contribution, together with some from A8, to the principal DA nigrostriatal pathway running to the striatum (caudate nucleus and putamen) and amygdala. This pathway is lateral to, but runs with, a more medial DA pathway, predominantly from A10, which innervates the nucleus accumbens and olfactory tubercle (mesolimbic pathway) as well as parts of the cortex (mesocortical system) such as the prefrontal and perirhinal cortex. The DA innervation to the anterior cingulate cortex also comes from A10 but with some axons from A9. There is in fact no clear divide between A9 and A10 and some overlap of their pathways. The DA mesolimbic tract and the noradrenergic bundles come together in the medial forebrain bundle before entering the cortex. Webster &2001 John Wiley & Sons Ltd 138 NEUROTRANSMITTERS, DRUGS AND BRAIN FUNCTION Figure 7. AMYG, amygdala; CN, caudate nucleus; MFB, medial forebrain bundle; NcA, nucleus accumbers; OT, olfactory tubercle; PUT, putamen; SN, substantia nigra. For full details see text and Moore and Bloom (1978) and Lindvall and Bjorkland (1978) A further totally separate DA pathway arises from A12 in the arcuate nucleus and forms the tuberoinfundibular tract in the median eminence to the pituitary gland for controlling prolactin release. This is partly achieved by DA being released into capillaries of the hypothalamic±hypophyseal portal system and then inhibiting the prolactin releasing cells (lactotrophs) of the anterior pituitary. While the nigrostriatal pathways are ipsilateral some crossing occurs in fibres from the ventral tegmental A10 nucleus. Further details can be obtained from Moore and Bloom (1978) and Lindvall and Bjorkland (1978). The nuclei provide distinct loci for activating the dopamine systems for electrophysiological, release and behavioural studies and for their destruction by electrolytic lesion or injection of the toxin 6-hydroxydopamine (6-OHDA). The concentration of DA in different brain areas of the rat is in keeping with the distribution of its pathways. It is concentrated in the striatum (10 mg/g), nucleus accumbens (5 mg/g) and olfactory tubercle (6 mg/g) but in the cortex there is much less (0. Cells in the substantia nigra in humans and primates differ from those in other species in containing granules of the lipoprotein pigment called neuromelanin. The melanin granules are free in the cytoplasm and give the SN a distinctive dark colour. Cells in this nucleus can also have hyaline inclusion bodies, the Lewy bodies, which are not common normally but appear to increase dramatically in patients with Parkinsonism. Certainly they will require considerable biochemical back-up to maintain function in all their terminals. NEUROCHEMISTRY The biochemical pathways in the synthesis and metabolism of dopamine are shown in Fig.