Reflex characteristics

Neurological symptoms result from demyelination of the spinal cord and are potentially irreversible. The symptoms and signs characteristic of a vitamin B 2 deficiency include paresthesis of the hands and feet, decreased deep-tendon reflexes, unsteadiness, and potential psychiatric problems such as moodiness, hallucinations, delusions, and psychosis. Neuropsychiatric disorders sometimes develop independently of the anemia, particularly in elderly patients. Visual loss may develop as a result of optic atrophy. 

The parallelization of crystallites, occurring as a result of fiber drawing, which consists in assuming by crystallite axes-positions more or less mutually parallel, leads to the development of texture within the fiber. In the case of PET fibers, this is a specific texture, different from that of other kinds of chemical fibers. It is called axial-tilted texture. The occurrence of such a texture is proved by the displacement of x-ray reflexes of paratropic lattice planes in relation to the equator of the texture dif-fractogram and by the deviation from the rectilinear arrangement of oblique diffraction planes. With the preservation of the principle of rotational symmetry, the inclination of all the crystallites axes in relation to the fiber axis is a characteristic of such a type of texture. The angle formed by the axes of particular crystallites (the translation direction of space lattice [c]) and the... 

The quantitative assessment of the degree of crystallite orientation by x-ray examination is not free of ambiguity. From a comparative analysis [23] in which results obtained from the consideration of (105) and from three different variations of equatorial reflection were compared, the conclusion was that the first procedure can lead to underrated results, i.e., to the underestimation of the orientation. However, it can be assumed that this does not result from an incorrect procedure, but from ignoring the fact that the adjacent (105) reflex can overlap. The absence of the plate effect of the orientation is characteristic of the orientation of crystallites in PET fibers. The evidence of this absence is the nearly identical azimuthal intensity distributions of the diffracted radiation in the reflexes originating from different families of lattice planes. The lack of the plate effect of orientation in the case of PET fiber stretching has to do with the rod mechanism of the crystallite orientation. 

The large diameter A/l-afferent fibre enters the dorsal horn of the spinal cord through the medial division of the dorsal root. It then descends through the medial region of lamina I or II, or alternatively, curves around the medial (central) edge of the dorsal horn down to the ventral horn. On reaching deeper laminae, laminae IV and V, the AjS-fibres ascend back up into laminae III and IV where they repeatedly subdivide and form a characteristic termination pattern. The densest arborisation appears to occur in lamina III. Axons originating from specialised muscle stretch receptors have collaterals that pass ventrally to make monosynaptic connections with neurons of laminae V, VI and VII. Some also extend to laminae VIII and IX of the ventral horn where they synapse directly onto motor neurons and form the basis of monosynaptic reflexes. 

Upper respiratory tract irritation can occur from inhalation of a medicinal gas, vapor, or aerosol. For assessing the potential of an inhalant to cause URT irritation, the mouse body plethysmographic technique (Alarie, 1966, 1981a, b) has proven to be extremely usefid. This technique operates on the principle that respiratory irritants stimulate the sensory nerve endings located at the surface of the respiratory tract from the nose to the alveolar region. The nerve endings in turn stimulate a variety of reflex responses (Alarie, 1973 Widdicombe, 1974) that result in characteristic changes in inspiratory and expiratory patterns and, most prominently, depression of respiratory rate. Both the potency of irritation and the concentration of... 

Each emotion is very complex and hence evolutionarily stable. It entails visceral adjustments, motoric responses, an affect, and extensive representation in the ancient subcortex. It is bound to be slow to evolve, hence Ekman s claim (1994, p. 16) that humans are unlikely to have evolved new emotions not found in other primates. Therefore, another useful criterion is presence in other primates. However, since every species has some unique characteristics, it is possible that some human emotions are absent from our primate relatives. For example, defecation may be purely reflexive in the arboreal primates but partly voluntary and hence emotional in our own species. Also, pair bonding is seen in humans but not chimpanzees. 

Neurohumoral (extrinsic) compensation involves two major mechanisms (previously presented in Figure 6-7)—the sympathetic nervous system and the renin-angiotensin-aldosterone hormonal response—plus several others. Some of the pathologic as well as beneficial features of these compensatory responses are illustrated in Figure 13-2. The baroreceptor reflex appears to be reset, with a lower sensitivity to arterial pressure, in patients with heart failure. As a result, baroreceptor sensory input to the vasomotor center is reduced even at normal pressures sympathetic outflow is increased, and parasympathetic outflow is decreased. Increased sympathetic outflow causes tachycardia, increased cardiac contractility, and increased vascular tone. Vascular tone is further increased by angiotensin II and endothelin, a potent vasoconstrictor released by vascular endothelial cells. The result is a vicious cycle that is characteristic of heart failure (Figure 13-3). Vasoconstriction increases afterload, which further reduces ejection fraction and cardiac output. Neurohumoral antagonists and vasodilators... 

Intradermal injection of histamine causes a characteristic red spot, edema, and flare response that was first described many years ago. The effect involves three separate cell types smooth muscle in the microcirculation, capillary or venular endothelium, and sensory nerve endings. At the site of injection, a reddening appears owing to dilation of small vessels, followed soon by an edematous wheal at the injection site and a red irregular flare surrounding the wheal. The flare is said to be caused by an axon reflex. A sensation of itching may accompany these effects. 

Some sedative-hypnotics, particularly members of the carbamate (eg, meprobamate) and benzodiazepine groups, exert inhibitory effects on polysynaptic reflexes and internuncial transmission and at high doses may also depress transmission at the skeletal neuromuscular junction. Somewhat selective actions of this type that lead to muscle relaxation can be readily demonstrated in animals and have led to claims of usefulness for relaxing contracted voluntary muscle in muscle spasm (see Clinical Pharmacology). Muscle relaxation is not a characteristic action of zolpidem, zaleplon, and eszopiclone. 

Further experimental evidence for the involvement of SP in pain perception came from knock-out animals. Mice, in which the preprotachykinin A gene was disrupted, showed significantly reduced responses in tests that involved more intense noxious stimuli (Cao et al., 1998). De Felipe et al. (1998) disrupted the N receptor, and found the characteristic amplification ( wind up ) and intensity coding of nociceptive reflexes to be absent. NK receptor knockout mice show no changes in acute nociception tests. In contrast, SP and NKi receptor knock-out mice show reduction in responses to inflammatory stimuli. Nerve injury-induced mechanical but not thermal hyperalgesia is attenuated in NKi receptor knock-out mice, when inducing chronic neuropathic pain by unilateral ligation of the L5 spinal nerve (Mansikka et al., 2000). 

Thiamine Deficiency and Brain Function Individuals with thiamine deficiency show some characteristic neurological signs and symptoms, including loss of reflexes, anxiety, and mental confusion. Why might thiamine deficiency be manifested by changes in brain function ... 

The second group involves polymers with three-dimensional ordering of side branches (e.g., those forming Mj-phaseXTable 5). On X-ray patterns of these polymers 3-4 narrow reflexes at wide angles are observed. As a rule, the authors define this type of structure as crystalline, or ascribe a smectic type of structure, characteristic for ordered smectics in SE or SH phases. The heats of transition from anisotropic state to isotropic melt are usually small and do not exceed the heats of transition smectic liquid crystal — isotropic melt . The similarity of structural parameters of three-dimensionally ordered smectics and that of crystalline polymers of the type here considered, make their correct identification quite a difficult task. 

Many clinical observations indicate that neurogenic factors in some way influence the development and maintenance of essential hypertension. It has long been recognized that stressful situations may induce marked increases in both systolic and diastolic pressures which persist for varying periods of time (21, 38), and that hypertensives tend to have a characteristic type of personality (2, 99. Such individuals usually exhibit important components of repressed antagonism and anxiety. They do not find emotional outlets in overt acts, but rather their emotions are expressed through an increased activity of the sympatho-adrenal system with a consequent increase in blood pressure. Relief of psychic tension frequently produces salutary effects in these patients. Individuals who show hyperactive sympathetic vasomotor reflexes (as measured by the cold pressor test) are much more prone than the average individual to develop hypertension in later life (57). 

Another characteristic of irritative stimulation of the trigeminal nerve is the defensive reflexes (e.g., sneezing) invoked by the body to remove or dilute the offending substance. In the case of oral chemical heat, the burning sensation from capsaicin invokes sweating, tearing, and copious salivation. Salivary flow... 

In foodborne botulism, complaints of nausea, vomiting, and diarrhea may accompany the initial neurologic symptoms. In later stages of the disease, constipation becomes more prominent. In infantile botulism, constipation is often the main symptom, along with characteristic flaccidity (the floppy baby ), poor suck reflex, poor feeding, and poor head control. 

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