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At least 109 records · Page 6Linked to original sources
PubMed1986

Modulation of transmission in rostral trigeminal sensory nuclei during chewing.

Eighty-one sensory neurons in the rostral trigeminal sensory nuclei (main sensory nucleus, nucleus oralis, and the lateral border zone of the motor nucleus) were recorded in urethan-anesthetized rabbits before and during mastication. Receptive-field characteristics were described, and responses evoked by electrical stimulation of the inferior alveolar and infraorbital nerves, sensorimotor cortex, and thalamus were recorded. Forty-four percent of neurons were stimulated by the movements of mastication; nevertheless, evidence is presented that the excitability of the 49 neurons that receive low-threshold mechanoreceptor inputs is depressed during mastication for the following reasons: The spontaneous activity of seven cells was inhibited during movement. The probability of firing in response to stimulation of the peripheral nerve on sensorimotor cortex was decreased during mastication. There was usually a corresponding increase in the latency of the action potentials. Injections of local anesthetic (prilocaine hydrochloride, 4%) into the receptive field of the neuron did not prevent the decrease in excitability during mastication. Fourteen neurons that received inputs from periodontal pressoreceptors were recorded medial to most of the low-threshold group. The excitability of six of these was reduced during jaw closure and during the occlusal phase of movement, that is, within the period in which they would be activated by pressure on the teeth. The rest were tonically suppressed. Eighteen neurons recorded in the lateral border zone of the motor nucleus had receptive fields that were of high threshold or were undefined. They responded to stimulation of the peripheral nerve at high threshold. The excitability of most of these neurons was strongly phase modulated during mastication. They were most excitable during jaw closure or during the occlusal phase of movement and inexcitable during opening. The excitability of the others was tonically depressed. In most cases, the changes in excitability described did not seem to be due to the patterns of activity of the neurons that were generated by the movements. We conclude that the pattern elaborated by the central pattern generator includes selective modifications of sensory transmission. One reason for this is to suppress reflex responses to low-threshold inputs while maintaining the protective response to tissue damage.

Alveolar Process↗
PubMed1994

Ageing and balance: the measurement of spontaneous sway by posturography.

Sway was measured by static posturography in 74 healthy subjects. Four age groups were investigated: 20-40, 40-60, 60-70 and over 70 years with equal numbers of males and females in each group. Sway increased linearly with age but was not affected by gender at any age. All age groups were more dependent on proprioception than vision in the maintenance of balance, but when reliable pressoreceptor information was removed, dependence on vision increased. The relative contributions of the sensory systems to balance did not alter with advancing age. The increase in sway demonstrated with normal ageing does not appear due to altered peripheral sensibility. It is more likely that it is due to slowing of central integrative processes.

Adult↗
PubMed1983

Ultrastructure of the corpuscular nerve ending in the lymph heart of the turtle (Pseudemys scripta elegans).

Corpuscular nerve endings were found in the tunica externa of the lymph heart of a turtle (Pseudemys scripta elegans). They consisted of axon terminals and surrounding cellular lamellae. Serial thin sections of one such presumable sensory corpuscle were made and reconstructed for the three-dimensional analysis of the corpuscle, with special reference to the axon terminals. It was revealed that axon terminals ramified at several points within the corpuscle and formed varicosities of various sizes ranging from 1.0 to 3.0 microns in diameter in their courses. Such varicosities contained an abundance of mitochondria as well as clear and granular vesicles 500 to 800 A in diameter. Finger-like protrusions often projected from the axon terminals into the interlamellar spaces. The lamellae consisted of several thin cytoplasmic processes of modified Schwann cells. The corpuscle was enclosed in an incomplete capsule consisting of a thin layer of cellular processes. The corpuscular nerve endings may represent pressoreceptors in the wall of the lymph heart.

Animals↗
PubMed1989

Does impulse noise induce vestibular disturbances?

The effect of impulse noise on postural stability was evaluated in 54 subjects from the Finnish army, who were suffering from acute hearing loss caused by exposure to firearms noise. For referents we used 20 non-exposed army recruits and 39 civilian volunteers. The effects of vision, pressoreceptor function and proprioception were stepwise excluded or altered, leaving mainly the vestibular guidance of postural control intact. Since the postural perturbation was fairly smooth during these instances we assume that the condition evaluates mainly the function of the otolith organs in guiding stance. We found no difference in any of the test conditions used, between normal controls, army controls and impulse noise exposed subjects. Furthermore, there was no dose response with body sway and severity of hearing loss. The results indicate that impulse noise may not be the cause of significant functional changes in the vestibular system that can account for noise-induced postural instability.

Adult↗
PubMed1975

[Syncope in glossopharyngeal neuralgia].

The case is presented of a 51-year-old man with symptomatic glossopharyngeal neuralgia who exhibited syncope during some of the neuralgic attacks. Clinically and pathophysiologically, these syncopes differ from the "carotid sinus syndrome" by the fact that they are caused by irritation of the sensory fibers of the IXth cerebral nerve instead of the pressoreceptors in the carotid sinus. While carbamazepine (Tegretol) had only transient beneficial effects, complete relief of symptoms was obtained by intracranial section of the glossopharyngeal nerve.

Carbamazepine↗
PubMed1991

Effects of venous return on respiratory response.

This study reevaluated the link between the rate of CO2 flow to the pulmonary circulation and changes in cardiac output to the respiratory responses following leg lifting in normal man subjects. Thirty healthy subjects (mean age = 22.2 years) were subjected to the experimental maneuver which increased venous return to the right heart. Cardiac output was significantly increased and with it a significant increase in CO2 output by the lungs was found. These results were associated with a significant increase in expired ventilation. The rapidity of the ventilatory response to the increase in cardiac output suggests the existence of pressoreceptors localized in the pulmonary circulation which, when activated, results in the elicitation of respiratory reflexes. The end result is an adjustment in the respiratory response in accordance with venous return.

Adult↗
PubMed1990

[Experimental studies on the transitional characteristics from touch sensation to pressure sensation in the mechanoreceptive sensation of periodontium].

Many studies have made on the physiological significance of the periodontium in relation to oral functions. But, although its importance to oral functions has been pointed out, few investigations have been carried out on the periodontal pressoreceptive information system. To help rectify this situation, as a link in investigations of soft-food textures, the author attempted to determine how a sense of pressure was perceived when loads gradually increasing from very small were applied to the tooth surface. In addition, the author attempted to clarify the way the periodontium discerns differences between initial and secondary loadings in a range of small loads between the touch sensation and the pressure sensation. Subjects were 10 males with sound, natural dentition and no disorders in mandibular functions. In order to eliminate intervention from pressoreceptors in the masticatory muscles and the mandibular joints, the upper first premolar was chosen as the test tooth. Small loads were applied in 2 directions: parallel to the first premolar vertical axis (vertical) and from the lingual to the buccal sides parallel to the occlusal plane (horizontal). For vertical loading, the mesial pit on the occlusal surface was chosen as the loading point. The middle point on the lingual surface was chosen as loading point for horizontal loading. First, loading on the tooth surface was gradually increased to obtain (1) threshold value for touch sensation; that is, minimal load required to incite a touch sensation, and (2) critical value for pressure sensation; that is, minimal load required to incite the pressure sensation subsequent to the touch sensation. Each subject was requested to press a hand switch in the moment he experienced the sensation of being touched and then again when, during increases of load, the touch sensation changed to the pressure sensation. The loading device was built into an electric strain gauge. Loads were increased gradually from 0 g to 60 g, with an increase ratio of about 10 g/sec. Loading wave and switching signal were simultaneously recorded on an oscillograph. Second, in order to determine the ability to discriminate small loads, with the same loading device, initial load was applied to the tooth. This load served as control. As soon as the load was sensed, it was removed. Then the secondary (testing) load was applied. Subjects were requested to say whether the secondary load was larger, smaller than or same as the initial one.(ABSTRACT TRUNCATED AT 400 WORDS)

Bite Force↗
PubMed1980

[Therapy of orthostatic dysregulation. Comparative studies on anti-hypotensive sympathomimetics with a tilt-table test].

In 7 patients suffering from orthostatic hypotension the early behaviour of arterial mean blood pressure was studied in the tilting table experiment under influence of etilefrine, norfenefrine, gepefrine (D-(+)-1-(3-hydroxyphenyl)-2-aminopropan-(2R, 3R)-hydrogentartrat) and of its I-isomere. Significant improvement of early orthostatic disregulation of the arterial pressure could be only observed under gepefrine. Amelioration seems to be induced by sensitization of the pressoreceptors.

Adult↗
PubMed1978

A mechanism to explain the antihypertensive action of propranolol.

The present experiments were designed to measure the direct effects of propranolol on carotid sinus pressoreceptor nerve activity in the semi-isolated, superfused sinus of the cat. Propranolol (5 microgram/ml) significantly enhanced carotid sinus nerve activity at perfusion pressures of 100, 150 and 250 mm Hg. The enhancement was due primarily to the recruitment of new fibers. In similar preparations, perfused at constant flow, propranolol increased sinus resistance in parallel with the increase in sinus discharge. These effects were rapidly dissipated by rinsing with drug-free perfusion solution. The evidence suggests that propranolol may produce a change in either the elastic or autoregulatory modalities of sinus smooth muscle. This may produce a functional "resetting" of the sinus and provide a mechanism to explain the antihypertensive effect of propranolol.

Action Potentials↗
PubMedDate not supplied

[Exercise test in young steers at 2800 M above sea level].

Among its different activities the Mexican Health Ministry (SSA) promotes: 1) the specification of biological standards for the Mexican population; 2) mechanisms for early detection of physiopathological changes and 3) development of the appropriate technology as a basis for primary health care. As part of this program we studied a random sample of students at the "Colegio de Bachilleres" of Cuajimalpa a suburban area of Mexico City, situated at 2800 m above sea level, part of the equipment used was produced at the Center for Development and Technological Applications (CE-DAT), an agency of SSA. Height, weight, heart rate (HR), systolic and diastolic blood pressures (SBP/DBP) were measured at rest in sitting position, standing up and walking on a treadmill. The results show a population with similar physical characteristics to those described for other populations in Mexico, with HR values within a homogeneous distribution, except for three subjects with rates larger than 2 standard deviations (SD). At standing up, women showed an orthostatic reflex of 27 beats/min and men of 22 beats/min. At the beginning of the exercise, the HR curve becomes more homogeneous, showing a discrete ascending slope with a low correlation coefficient, suggesting low physical capacity of the studied population. As exercise continued, some subjects showed a low increment of HR, giving values differing by 2 SD. Five women and three men had resting SBP values lying 2 SD out of the mean values of the sample. During exercise, SBP increases 28 mmHg as average. Notwithstanding the low cardiac response, the time spent on the treadmill lies within the levels considered as good and, even, excellent, on the table of the National Institute of Cardiology. We discuss new procedures to analyze instantaneously the HR and the pressoreceptor reflex as well as their functional significance.

Adolescent↗