By E. Jens. University of Medicine and Dentistry of New Jersey. 2018.
Individuals may persistently reex- tressing that they impair social or occupa- perience the event in distressing images order skelaxin 400 mg with mastercard spasms everywhere, tional function generic 400mg skelaxin free shipping muscle relaxant otc cvs. Because physical symp- nightmares, or ﬂashbacks; they may avoid toms are often similar to symptoms of a reminders of the event, including persons variety of medical conditions, individuals or places; or they may have hyperarousal may receive medical treatment for their symptoms, such as insomnia, irritability, symptoms even though no organic cause impaired concentration, or hypervigilance can be found. Individuals may demon- Individuals with somatization disorder strate little emotion or appear detached do not consciously produce the symptoms and lose interest in previously enjoyed ac- but truly experience them, even though tivities or in important close relationships. Although many individuals experience Conversion Disorder acute forms of PTSD at some time during their life, most recover. When PTSD per- Another type of somatoform disorder is sists, it can be debilitating and require psy- conversion disorder, in which individuals chological and pharmacologic interven- lose a physical function, often related to a tion (Ursano, 2002). Symp- nature of their condition and can facilitate toms do not typically follow a pattern that recovery. Cognitive therapy and anxiety would correspond to a speciﬁc disease or management therapies can also be help- injury. Hypochondriasis Somatoform Disorders Hypochondriasis, another type of som- atoform disorder, is characterized by pre- Somatoform disorders are conditions in occupation with physical illness. Indi- which individuals experience physical viduals with this condition may fear or symptoms for which no organic cause can believe they have a serious physical illness Common Psychiatric Disabilities 189 or perceive the symptoms of a coexisting new identity without being able to recall disease or condition in an exaggerated their previous identity. For example, they may perceive a sia is the inability to recall events that cough associated with a common cold as occurred within a certain period of time a sign of tuberculosis or lung cancer. Dissociative Pain Disorder identity disorder, formerly known as multi- ple personality disorder, is a condition in Pain disorder is a preoccupation with which at least two personalities exist with- pain that is severe enough to cause in the same individual and control the impairment in function at home, school, individual’s behavior. Personality Disorders Individuals with pain disorder do not con- sciously produce the symptoms of a pain Everyone has personality traits or char- and actually experience the pain report- acteristics. This disorder can be extremely inca- they can interfere with the ability to func- pacitating, often severely limiting social tion, especially during times of crisis. Personality disorders describe disorders characterized by inﬂexible or maladaptive Factitious Disorders behaviors that have usually lasted a long time and that impair interpersonal or Although not severely disabling, a vari- occupational functioning or cause subjec- ety of other types of mental disorders may tive distress (American Psychiatric Asso- interfere with effective functioning. They may assume the sick role (American Psychiatric rationalize their actions, blaming others Association, 2000). A factitious disorder for their situation or misfortune without differs from malingering (in which indi- examining their own responsibility for the viduals also produce symptoms intention- situation at hand. When a personality disorder exists in combination with other mental Dissociative Disorders disorders, the prognosis is more guarded, and treatment and management of the Conditions in which individuals expe- personality disorder are more difﬁcult. At rience an alteration in memory, conscious- times, these individuals may not have a ness, or identity for no organic reason are full-blown personality disorder but rather called dissociative disorders. Dissociative maladaptive personality traits that may fugue is a condition in which individuals interfere with the treatment or diagnosis leave their environment and assume a of the concomitant disorder. The diagnosis of mental conditions is The most commonly used intelligence often an art as well as a science. It requires tests are the Wechsler Intelligence Scale for skill and experience on the part of those Children-Revised, the Wechsler Preschool evaluating individuals’ symptoms and and Primary Scale of Intelligence, the interpreting the results of the various tests Stanford-Binet, and the Wechsler Adult designed to measure psychological or intel- Intelligence Scale-Revised. Many professionals may The limitations of intelligence testing be involved in testing and evaluation; psy- originate from: chiatrists and clinical psychologists are fre- • the difﬁculty of tapping all aspects of quently involved in the diagnosis of intellectual ability mental disorders. Diagnosis is usually • the individual’s ability to take the test based on information from a variety of dif- • the degree to which the test measures ferent sources. There is considerable individual can be obtained through psychological variability in abilities, however, and results testing. Psychological tests may be used to of intelligence tests, like results of other evaluate intelligence, personality, or forms of psychological tests, must be eval- behavior. Much vide partial information needed for the ac- intelligence testing involves sampling curate diagnosis of a mental condition. No individuals’ intellectual capacity in a vari- single test is adequate to offer a deﬁnitive ety of different spheres. Often, because on cognitive processes, including problem mental disorders affect a variety of func- solving, adaptive thinking, and other tions, several psychological tests that aspects of performance. Tests alone should measure different functions may be nec- not determine a deﬁnitive diagnosis. Mental Status Examination and Intelligence Tests Assessment Through Interviews The term intelligence is difﬁcult to deﬁne. The structured interview is one way in Theoretically, intelligence consists of a num- which the mental functioning of individ- ber of skills and abilities, some of which uals with a suspected mental disorder may cannot be measured.
Not all influences on best 400 mg skelaxin spasms nose, or potentials recorded from discount skelaxin 400 mg online uterus spasms 38 weeks, a neuron have the same time-course as the EPSP and IPSP, which follow the rapid opening of Na and Cl7 ion channels directly linked to NT receptors. There are also slowly developing, longer lasting and smaller non-propagated (conditioning) changes in potential most of which appear to have a biochemical intermediary in the form of G-proteins linked to the activation (Gs) or 14 NEUROTRANSMITTERS, DRUGS AND BRAIN FUNCTION Figure 1. Resting membrane potential (770 mV) is maintained by Na influx and K efflux. Varying degrees of depolarisation, shown by different sized EPSPs (a and b), are caused by increasing influx of Na. When the membrane potential moves towards threshold potential (60±65 mV) an action potential is initiated (c). They can be excitatory (depolarising) or inhibitory (hyperpolarising) generally involving the opening or closing of K channels. This can be achieved directly by the G- protein or second messenger but more commonly by the latter causing membrane phosphorylation through initiating appropriate kinase activity. Thus the activity of a neuron can be controlled in a number of ways by NTs activating appropriate receptors (Fig. Two basic receptor mechanisms are involved: (1) Ionotropic Those linked directly to ion channels such as those for Na (e. ACh nicotinic or some glutamate receptors) or Cl7 (GABA), involving fast events with increased membrane conductance and ion flux. With these the first messenger of synaptic transmission, the NT, activates a second messenger to effect the change in neuron excitability. They are normally associated with reduced membrance conductance and ion flux (unless secondary to NEUROTRANSMITTER SYSTEMS AND FUNCTION: OVERVIEW 15 Figure 1. In the former the neurotransmitter combines with a receptor that is directly linked to the opening of an ion channel (normally Na or C17) while in the latter the receptor activates a G-protein that can directly interact with the ion channel (most probably K or Ca2) but is more likely to stimulate (Gs) or inhibit (Gi) enzymes controlling the levels of a second messenger (e. These in turn may also directly gate the ion channel but generally control its opening through stimulating a specific protein kinase that causes phosphorylation of membrane proteins and a change in state of the ion channel. The latter (metabotropic) effects may either open or close an ion channel (often K) and are much slower (100s ms to min) than the ionotropic ones (1±10 ms). A variety of neuro- transmitters, receptors, second messengers and ion channels permits remarkably diverse and complex neuronal effects an increased Ca2 conductance) and may involve decreased Na influx (inhibitory) or K efflux (excitatory). These two basic mechanisms could provide a further classification for NTs, namely fast and slow acting, although one NT can work through both mechanisms using different receptors. The slow effects can also range from many milliseconds to seconds, minutes, hours or even to include longer trophic influences. What will become clear is that while one NT can modify a number of different membrane ion currents through different mechanisms and receptors, one current can also be affected by a number of different NTs. The control of neuronal excitability is discussed in more detail in Chapter 2. It has been known for many years that stimulation of muscle or cutaneous afferents to one segment of the spinal cord produces a prolonged inhibition of motoneuron activity without any accompanying change in conductance of the motoneuron membrane, i. Such inhibition is probably, therefore, of presynaptic origin and is, in fact, associated with a depolarisation of the afferent nerve terminals and a reduction in release of the excitatory NT. If it is assumed that the amount of NT released from a nerve terminal depends on the amplitude of the potential change induced in it, then if that terminal is already partly depolarised when the impulse arrives there will be a smaller change in potential and it will release less transmitter (Fig. There is no direct evidence for this concept from studies of NT release but electrophysiological experiments at the crustacean neuromuscular junction, which has separate excitatory and inhibitory inputs, show that stimulation of the inhibitory nerve, which released GABA, reduced the EPSP evoked postsynaptically by an excitatory input without directly hyperpolarising (inhibiting) the muscle fibre. Certainly when GABA is applied to various in vivo and in vitro preparations (spinal cord, cuneate nucleus, olfactory cortex) it will produce a depolarisation of afferent nerve terminals that spreads sufficiently to be recorded in their distal axons. Such presynaptic inhibition can last much longer (50±100 ms) than the postsynaptic form (5 ms) and can be a very effective means of cutting off one particular excitatory input without directly reducing the overall response of the neuron. How GABA can produce both presynaptic depolarisation and conventional postsynaptic hyperpolar- isation by the same receptor, since both effects are blocked by the same antagonist, bicuculline, is uncertain (see Chapter 2) although an increased chloride flux appears to be involved in both cases. If nerve terminals are depolarised, rather than hyper- polarised by increased chloride flux, then their resting membrane potential must be different from (greater than) that of the cell body so that when chloride enters and the potential moves towards its equilibrium potential there is a depolarisation instead of a hyperpolarisation.
This oc- Control by Inhibitory Motor Neurons of the Length of In- curs coincidently with control of contractile strength discount skelaxin 400mg with mastercard spasms hamstring. Con- testine Occupied by a Contraction and the Direction of tractions can only occur in segments where ongoing inhi- Propagation of Contractions 400 mg skelaxin with visa spasms muscle. 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. At the same time, the longitudinal During emesis (vomiting), powerful propulsive peristalsis muscle of the esophagus and the gastroesophageal junc- starts in the midjejunum and travels to the stomach. The overall result is the formation of a funnel- result, the small intestinal contents are propelled rapidly like cavity that allows the free flow of gastric contents into and continuously toward the stomach. As the propulsive the esophagus as intra-abdominal pressure is increased by complex advances, the gastroduodenal junction and the contraction of the diaphragm and abdominal muscles dur- stomach wall relax, allowing passage of the intestinal con- ing retching. CHAPTER 26 Neurogastroenterology and Gastrointestinal Motility 465 Inhibitory motor neurons Lower esophageal Lower esophageal sphincter sphincter (closed) Active (open) Inactive Pylorus Pylorus (closed) (open) Inhibitory motor neurons FIGURE 26. GI sphinc- ters are closed when Internal anal Inactive their inhibitory innerva- Active Internal anal sphincter tion is inactive. The sphincter (closed) (open) sphincters are opened by active firing of the in- hibitory motor neurons. When this occurs, the inhibitory neurotrans- Peristalsis Is a Stereotyped Propulsive mitter relaxes the ongoing muscle contraction in the sphinc- Motor Reflex teric muscle and prevents excitation and contraction in the adjacent muscle from spreading into and closing the Peristalsis is the organized propulsion of material over vari- sphincter. The muscle lay- ers of the intestine behave in a stereotypical pattern during peristaltic propulsion (Fig. During peri- BASIC PATTERNS OF GI MOTILITY stalsis, the longitudinal muscle layer in the segment ahead Motility in the digestive tract accounts for the propulsion, of the advancing intraluminal contents contracts while the mixing, and reservoir functions necessary for the orderly circular muscle layer simultaneously relaxes. The intestinal processing of ingested food and the elimination of waste tube behaves like a cylinder with constant surface area. Propulsion is the controlled movement of in- shortening of the longitudinal axis of the cylinder is ac- gested foods, liquids, GI secretions, and sloughed cells companied by a widening of the cross-sectional diameter. It moves the The simultaneous shortening of the longitudinal muscle food from the stomach into the small intestine and along and relaxation of the circular muscle results in expansion of the small intestine, with appropriate timing for efficient di- the lumen, which prepares a receiving segment for the for- gestion and absorption. Propulsive forces move undigested ward-moving intraluminal contents during peristalsis. Trituration, the crushing and grinding havior is contraction of the circular muscle in the segment of ingested food by the stomach, decreases particle size, in- behind the advancing intraluminal contents.
The otocyst further differentiates to form a dorsal utricular portion and a ventral saccular portion discount 400mg skelaxin mastercard spasm. Three separate diverticula extend outward from the utricular por- tion and develop into the semicircular canals skelaxin 400 mg low price muscle relaxant and pregnancy, which later func- tion in balance and equilibrium. A tubular diverticulum called the cochlear duct extends in a coiled fashion from the saccular portion and forms the membranous portion of the cochlea of the ear (exhibit II). The spiral organ, which is the functional por- tion of the cochlea,differentiates from cells along the wall of the cochlear duct (Ex. The sensory nerves that innervate the inner ear are derived from neuroectoderm from the developing brain. The differentiating otocyst is surrounded by mesodermal tissue that soon forms a cartilaginous otic capsule (exhibit III). As the otocyst and surrounding otic capsule grow, vacuoles con- taining the fluid perilymph form within the otic capsule. The vacuoles soon enlarge and coalesce to form the perilymphatic space, which divides into the scala tympani and the scala vestibuli. Eventually, the cartilaginous otic capsule ossifies to form the bony (osseous) labyrinth of the inner ear. The middle- ear chamber is referred to as the tympanic cavity and derives from the first pharyngeal pouch (exhibit IV). The auditory ossi- cles, which amplify incoming sound waves, derive from the first and second pharyngeal arch cartilages. As the tympanic cavity enlarges, it surrounds and encloses the developing ossicles (ex- hibit IV). The connection of the tympanic cavity to the pharynx gradually elongates to develop into the auditory (eustachian) tube, which remains patent throughout life and is important in maintaining an equilibrium of air pressure between the pharyn- geal and tympanic cavities. The outer ear includes the fleshy auricle attached to the side of the head and the tubular external acoustic canal that ex- tends into the external acoustic meatus of the temporal bone of the skull. The external acoustic canal forms from the surface ec- toderm that covers the dorsal end of the first branchial groove (Ex. A solid epithelial plate called the meatal plug soon develops at the bottom of the funnel-shaped branchial groove. The meatal plug is involved in the formation of the inner wall of the external acoustic canal and contributes to the tympanic membrane (eardrum). The tympanic membrane has a dual origin from surface ectoderm and the endoderm lining the first pharyn- geal pouch (exhibit IV). EXHIBIT III The formation of the cochlea and the spiral organ from the otic capsule. Successive stages of development of the perilymphatic space and the spiral organ from the eighth to the twentieth week. Sensory Organs © The McGraw−Hill Anatomy, Sixth Edition Coordination Companies, 2001 (concluded) EXHIBIT IV The development of the outer- and middle-ear regions and the auditory ossicles (malleus, incus, and stapes). An embryo afflicted with rubella is 30% more likely to be Other severe malformations, which are incompatible with life, aborted, stillborn, or congenitally deformed than one that is not are generally expressed with this condition. Rubella interferes with the mitotic process, and thus causes underdeveloped organs. An embryo with rubella may suf- Ear fer from a number of physical deformities, including cataracts and Congenital deafness is generally caused by an autosomal reces- glaucoma, which are common deformities of the eye. The actual functional impairment is generally either a defective Eye set of auditory ossicles or improper development of the neurosen- Most congenital cataracts are hereditary, but they may also be sory structures of the inner ear. In this condition, the lens is abnormalities are not uncommon, especially in infants opaque and frequently appears grayish white. Functional Impairments of the Eye Emmetropia No correction necessary (normal vision) Few people have perfect vision. Slight variations in the shape of Rays focus on retina the eyeball or curvature of the cornea or lens cause an imperfect (a) focal point of light rays onto the retina. Most variations are slight, however, and the error of refraction goes unnoticed. Se- vere deviations that are not corrected may cause blurred vision, fatigue, chronic headaches, and depression. The primary clinical considerations associated with defects in the refractory structures or general shape of the eyeball are myopia, hyperopia, presbyopia, and astigmatism.
The cerebellum consists of two (a) The cell body contains the nucleus discount skelaxin 400 mg amex muscle relaxant toxicity, instigation of voluntary movement cheap skelaxin 400mg fast delivery muscle relaxant methocarbamol addiction, the hemispheres connected by the vermis and chromatophilic substances, storage of memory, thought processes, and supported by three paired cerebellar neurofibrils, and other organelles. The cerebral cortex is convoluted with (a) The cerebellum is composed of a axon conducts action potentials away gyri and sulci. Neuroglia are of six types: frontal, parietal, temporal, and occipital convoluted cortex of gray matter. The insula lies deep within the (b) The cerebellum is concerned with around axons in the PNS; cerebrum and cannot be seen in an coordinated contractions of skeletal oligodendrocytes form myelin layers external view. Brain waves generated by the cerebral perform a phagocytic function in the cortex are recorded as an Myelencephalon (pp. The medulla oblongata is composed of the substances from the blood to the CNS; valuable diagnostic information. The white matter of the cerebrum consists spinal cord and contains nuclei for several cerebrospinal fluid in the CNS; and of association, commissural, and autonomic functions. Basal nuclei are specialized masses of gray reticular activating system in arousing the (a) The neuroglia that surround an axon matter located within the white matter of cerebrum. The diencephalon is a major autonomic outer periosteal layer and an inner 4. The thalamus is an ovoid mass of gray a single layer surrounded by the vascular (a) Sensory (afferent) neurons are matter that functions as a relay center for epidural space. The hypothalamus is an aggregation of surrounding the subarachnoid space, multipolar. The epithalamus contains the pineal smooth muscle, cardiac muscle, gland and the vascular choroid plexus and glands. Nervous Tissue and the © The McGraw−Hill Anatomy, Sixth Edition Coordination Central Nervous System Companies, 2001 398 Unit 5 Integration and Coordination Ventricles and Cerebrospinal Fluid 4. The blood-brain barrier determines which (b) The conus medullaris is the terminal (pp. The lateral (first and second), third, and the extracellular fluid of the brain. Ascending and descending spinal cord continuous with the central canal of the 1. Cerebrospinal fluid is continuously formed and two longitudinal grooves that decussate (cross over) in the spinal by the choroid plexuses from blood plasma partially divide it into right and left cord or in the medulla oblongata of and is returned to the blood at the halves. Beside each Match the following structures of the brain to (d) the vermis. The structure of the brain that is most basic functional units of the nervous system? List the six principal types of neuroglia (c) mesencephalon (c) the medulla oblongata. Why is it called an all-or-none sheaths in the peripheral nervous system are (a) They are located within the response? A collection of neuron cell bodies located (d) They indirectly exert an inhibitory 8. The corpora quadrigemina, red nucleus, major part of the autonomic nervous (b) a nerve. List the nuclei located (a) sensory neurons in the midbrain and state the function (b) somatic motor neurons (c) the mesencephalon. Describe the location and structure of the (d) autonomic motor neurons 12. Describe the formation of the neural crest CT scan, MS, DSR, and CVA stand for? Nervous Tissue and the © The McGraw−Hill Anatomy, Sixth Edition Coordination Central Nervous System Companies, 2001 Chapter 11 Nervous Tissue and the Central Nervous System 399 14. What causes it and how complains of loss of sensation from the specific irritable tissue, such as a tumorous is it controlled? Electrical stimulation of the cerebellum or before a focal seizure, the sufferer these conditions differ? How would damage to these called an aura, that suggests the origin of Critical-Thinking Questions two regions of the brain affect skeletal the electrical burst. If an entire cerebral hemisphere is origin of a seizure that was preceded by of body structures are reported. A flash of brief case study of a patient who has suffered damage to the medulla oblongata, a much light.
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