scholarly journals Pulmonary and respiratory tract receptors.

1982 ◽  
Vol 100 (1) ◽  
pp. 41-57
Author(s):  
J G Widdicombe
Keyword(s):  
Respiratory Tract ◽  
Large Diameter ◽  
Small Diameter ◽  
Spinal Reflexes ◽  
Mechanical Stimuli ◽  
Nerve Fibres ◽  
Motor Responses ◽  
Myelinated Fibres ◽  
Set Up ◽  
Stimulation Of

Nervous receptors in the lungs and respiratory tract can be grouped into four general categories. 1. Deep, slowly adapting end-organs, which respond to stretch of the airway wall and have large-diameter myelinated fibres; those in the lungs are responsible for the Breuer-Hering reflex. 2. Endings in and under the epithelium which respond to a variety of chemical and mechanical stimuli (i.e. are polymodal), usually with a rapidly adapting discharge, and with small-diameter myelinated fibres; they are responsible for defensive reflexes such as cough and sneeze, and for the reflex actions to inhaled irritants and to some respiratory disease processes. 3. Receptors with nonmyelinated nerve fibres which, being polymodal, are stimulated by tissue damage and oedema and by the mediators released in these conditions; these receptors may be similar in function to 'nociceptors' in other viscera, and set up appropriate reflexes as a reaction to respiratory damage. 4. Specialized receptors such as those for taste and swallowing, and those around joints and in skeletal muscle. Stimulation of any group of receptors may cause reflex changes in breathing (including defensive reflexes), bronchomotor tone, airway mucus secretion, the cardiovascular system (including the vascular bed of the airways), laryngeal calibre, spinal reflexes and sensation. The total pattern of motor responses is unique for each group of receptors, although it is probably unusual for one type of receptor to be stimulated in isolation. The variety of patterns of motor responses must reflect the complexity of brainstem organization of these systems.

Depression of Nociceptive Sensory Activity in the Rat Spinal Cord Due to the Intrathecal Administration of Drugs: Effect of Diazepam

Neurosurgery ◽  
1984 ◽  
Vol 15 (6) ◽  
pp. 917-920 ◽  
Author(s):  
Ilmar Jurna
Keyword(s):  
Spinal Cord ◽  
Substance P ◽  
Nerve Fibers ◽  
Afferent Nerve ◽  
Spinal Reflexes ◽  
Sensory Response ◽  
Motor Responses ◽  
Afferent Nerve Fibers ◽  
C Fiber ◽  
Stimulation Of

Abstract The intrathecal (i.t.) administration of morphine inhibits nociceptive motor responses and activity in ascending axons evoked by stimulation of nociceptive afferent nerve fibers (nociceptive sensory response) in the rat. The i.t. administration of cholecystokinin octapeptide and ceruletide inhibits nociceptive motor responses, but does not affect ascending nociceptive activity. This shows that drug-induced depression of nociceptive motor responses is not always associated with depression of the nociceptive sensory response of the spinal cord. The microiontophoretic application of substance P excites single dorsal horn neurons that respond to noxious stimulation, whereas the i.t. administration of substance P inhibits both nociceptive motor and sensory responses. Thus, the results obtained from the i.t. administration of a drug may differ from those obtained from its application to single spinal neurons. Diazepam inhibits spinal reflexes and may reduce pain sensation in humans. To assess whether a spinal action is involved in the pain-relieving effect of diazepam, experiments were carried out on spinalized rats in which activity evoked by the stimulation of nociceptive and nonnociceptive afferent nerve fibers of the sural nerve was recorded from single ascending axons below the site of spinal cord transection. Diazepam, 20 ųg i.t., reduced activity evoked by afferent A delta and C fiber stimulation and by stimulation of afferent A beta fibers. The depressant effect caused by diazepam, 2 mg/kg i.v., on C fiber-evoked ascending activity was reduced by the i.t. injection of the benzodiazepine antagonist, Ro 15-1788 (40 ųg), an imidazodiazepine. It is concluded that the depression by diazepam of C fiber-evoked ascending activity contributes to pain relief caused by the drug.

The innervation of the joint and its role in osteoarthritis pain

2016 ◽  
Author(s):  
Jason J. McDougall ◽  
Joel A. Vilensky
Keyword(s):  
Firing Rate ◽  
Large Diameter ◽  
Small Diameter ◽  
Position Sense ◽  
Joint Position Sense ◽  
Sensory Nerves ◽  
Peripheral Sensitization ◽  
Mechanical Stimuli ◽  
Joint Afferents ◽  
Joint Pathology

Diarthrodial joints possess an extensive network of sensory and sympathetic nerve fibres whose physiological functions are varied and complex. Nerves are primarily located in the synovium but also innervate the subchondral bone, the outer third of menisci, and the superficial surface of tendons and ligaments. Large-diameter, myelinated neurons are involved in joint position sense while small-diameter neurons with thin or no myelin typically sense pain. The small-diameter nerves in conjunction with sympathetic fibres control synovial blood flow and maintain joint homeostasis. In patients with osteoarthritis (OA), the sensory nerves become sensitized and increase their firing rate in response to normal movement. This peripheral sensitization is mediated by numerous algogenic agents released into the OA knee including neuropeptides, eicosanoids, and proteinases. A portion of joint afferents fire in the absence of mechanical stimuli and encode pain at rest. Interestingly, the firing rate of joint afferents does not correlate with OA severity, indicating that pain is a poor predictor of joint pathology. Evidence is accumulating to suggest that a subpopulation of OA patients who are unresponsive to classical non-steroidal anti-inflammatory drugs may be suffering from neuropathic pain in which there is damage to the joint nerves themselves. Better understanding of the biology of joint nerves could help in the development of patient-targeted therapies to alleviate OA pain and inflammation.

Differences in the brain stem terminations of large- and small-diameter vestibular primary afferents

1995 ◽  
Vol 74 (3) ◽  
pp. 1362-1366 ◽  
Author(s):  
J. A. Huwe ◽  
E. H. Peterson
Keyword(s):  
Brain Stem ◽  
Large Diameter ◽  
Small Diameter ◽  
Movement Control ◽  
Three Dimensions ◽  
Significant Shift ◽  
Axon Diameter ◽  
Vestibular Complex ◽  
The Brain ◽  
Adjacent Brain

1. We visualized the central axons of 32 vestibular afferents from the posterior canal by extracellular application of horseradish peroxidase, reconstructed them in three dimensions, and quantified their morphology. Here we compare the descending limbs of central axons that differ in parent axon diameter. 2. The brain stem distribution of descending limb terminals (collaterals and associated varicosities) varies systematically with parent axon diameter. Large-diameter afferents concentrate their terminals in rostral regions of the medial/descending nuclei. As axon diameter decreases, there is a significant shift of terminal concentration toward the caudal vestibular complex and adjacent brain stem. 3. Rostral and caudal regions of the medial/descending nuclei have different labyrinthine, cerebellar, intrinsic, commissural, and spinal connections; they are believed to play different roles in head movement control. Our data help clarify the functions of large- and small-diameter afferents by showing that they contribute differentially to rostral and caudal vestibular complex.

Supraspinal inhibition of a cutaneous vascular reflex in the cat

1964 ◽  
Vol 207 (2) ◽  
pp. 303-307 ◽  
Author(s):  
B. J. Prout ◽  
J. H. Coote ◽  
C. B. B. Downman
Keyword(s):  
Carotid Sinus ◽  
Spinal Reflexes ◽  
Descending Pathways ◽  
Skin Response ◽  
Reflex Arc ◽  
Vascular Reflex ◽  
Carotid Sinus Nerve Stimulation ◽  
Sympathetic Discharge ◽  
Stimulation Of ◽  
Cerebellar Stimulation

In cats anesthetized with chloralose-urethane mixture, stimulation of an afferent nerve evoked a vasoconstrictor reflex (VCR) and a galvanic skin response (GSR) in the pads of the feet. Stimulation of the ventromedial medullary reticular substance at the level of the obex abolished the VCR and the GSR. VCR could also be reduced by occlusion during prolonged stimulation of another spinal or visceral afferent pathway. Medulla stimulation was effective without itself causing a sympathetic discharge to the paw, showing that inhibition rather than occlusion was operative. Anterior cerebellar stimulation also inhibited the VCR. Carotid sinus nerve stimulation did not abolish the VCR. It is concluded that the effective mechanism includes a bulbospinal inhibitory path projecting on a spinal vasoconstrictor reflex arc. This arrangement is similar to the descending pathways inhibiting other spinal reflexes but the VCR-inhibitory path can be activated independently of them.

scholarly journals Elastic Modulus and Elasticity Ratio of Malignant Breast Lesions with Shear Wave Ultrasound Elastography: Variations with Different Region of Interest and Lesion Size

Diagnostics ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1015
Author(s):  
Antonio Bulum ◽  
Gordana Ivanac ◽  
Eugen Divjak ◽  
Iva Biondić Špoljar ◽  
Martina Džoić Dominković ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Shear Wave ◽  
Large Diameter ◽  
Small Diameter ◽  
Shear Wave Elastography ◽  
Lesion Size ◽  
Ultrasound Elastography ◽  
Breast Lesions ◽  
Malignant Breast ◽  
The Impact

Shear wave elastography (SWE) is a type of ultrasound elastography with which the elastic properties of breast tissues can be quantitatively assessed. The purpose of this study was to determine the impact of different regions of interest (ROI) and lesion size on the performance of SWE in differentiating malignant breast lesions. The study included 150 female patients with histopathologically confirmed malignant breast lesions. Minimal (Emin), mean (Emean), maximal (Emax) elastic modulus and elasticity ratio (e-ratio) values were measured using a circular ROI size of 2, 4 and 6 mm diameters and the lesions were divided into large (diameter ≥ 15 mm) and small (diameter < 15 mm). Highest Emin, Emean and e-ratio values and lowest variability were observed when using the 2 mm ROI. Emax values did not differ between different ROI sizes. Larger lesions had significantly higher Emean and Emax values, but there was no difference in e-ratio values between lesions of different sizes. In conclusion, when measuring the Emin, Emean and e-ratio of malignant breast lesions using SWE the smallest possible ROI size should be used regardless of lesion size. ROI size has no impact on Emax values while lesion size has no impact on e-ratio values.

scholarly journals A Novel Bioreactor for the Mechanical Stimulation of Clinically Relevant Scaffolds for Muscle Tissue Engineering Purposes

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 474
Author(s):  
Silvia Todros ◽  
Silvia Spadoni ◽  
Edoardo Maghin ◽  
Martina Piccoli ◽  
Piero G. Pavan
Keyword(s):  
Mechanical Stimulation ◽  
Strain Range ◽  
Tensile Tests ◽  
Muscular Tissue ◽  
Fe Model ◽  
Mechanical Stimuli ◽  
Physiological Strain ◽  
Cellular Alignment ◽  
Stimulation Of

Muscular tissue regeneration may be enhanced in vitro by means of mechanical stimulation, inducing cellular alignment and the growth of functional fibers. In this work, a novel bioreactor is designed for the radial stimulation of porcine-derived diaphragmatic scaffolds aiming at the development of clinically relevant tissue patches. A Finite Element (FE) model of the bioreactor membrane is developed, considering two different methods for gripping muscular tissue patch during the stimulation, i.e., suturing and clamping with pliers. Tensile tests are carried out on fresh and decellularized samples of porcine diaphragmatic tissue, and a fiber-reinforced hyperelastic constitutive model is assumed to describe the mechanical behavior of tissue patches. Numerical analyses are carried out by applying pressure to the bioreactor membrane and evaluating tissue strain during the stimulation phase. The bioreactor designed in this work allows one to mechanically stimulate tissue patches in a radial direction by uniformly applying up to 30% strain. This can be achieved by adopting pliers for tissue clamping. Contrarily, the use of sutures is not advisable, since high strain levels are reached in suturing points, exceeding the physiological strain range and possibly leading to tissue laceration. FE analysis allows the optimization of the bioreactor configuration in order to ensure an efficient transduction of mechanical stimuli while preventing tissue damage.

Analysis Influence of Pile Embedded Depth and Diameter on Pile Tip Resistance

2013 ◽  
Vol 353-356 ◽  
pp. 459-462
Author(s):  
Ying Jie Zheng ◽  
Bin Fang ◽  
Lian Xiang Li
Keyword(s):  
Large Diameter ◽  
Small Diameter ◽  
Stiffness Ratio ◽  
Initial Stiffness ◽  
Tip Resistance

Pile tip absolute settlement curves and relative settlement curves of several working cases were analyzed. It is found that load-settlement curve characteristic related to the selection standard. The tip resistance initial stiffness of each case was analyzed. Results show that the small diameter pile has higher initial stiffness than large diameter pile, embedded depth has little influence on initial stiffness ratio, but increment of initial stiffness is linear with embedded depth growth.

The synaptic organization of optic afferents in the amphibian tectum

1974 ◽  
Vol 187 (1089) ◽  
pp. 421-447 ◽  
Keyword(s):  
Optic Nerve ◽  
Cell Layer ◽  
Maximum Amplitude ◽  
Synaptic Organization ◽  
Nerve Fibres ◽  
Synaptic Potentials ◽  
Postsynaptic Cell ◽  
Optic Fibre ◽  
Stimulation Of

Potentials in the amphibian tectum, evoked by stimulation of the optic nerve, were recorded extracellularly. Four discrete potentials, referred to as the m 1 , m 2 , u 1 and u 2 waves, occur at different latencies after stimulation. We have shown that these waves represent summed post-synaptic potentials generated by synchronous activation of four different groups of optic nerve fibres. The m 1 and m 2 waves are generated by two classes of myelinated optic nerve fibres, previously characterized as ‘dimming’ and ‘event’ fibres. The maximum amplitude of the m 2 wave occurs just below, and of the m 2 wave just above, cell layer 8 of P. Ramón. The u 1 and u 2 waves are generated by ‘edge’ and ‘convexity’ fibres, respectively. The maximum amplitude of the u 1 wave occurs near the surface of the tectum, and of the u 2 wave some 100 μm below it. Postsynaptic cell bodies for all four classes of optic fibre are located in layer 8.

THE MOTILITY AND REACTIVITY OF THE OESTROGENIZED RABBIT UTERUS IN VIVO; WITH COMPARATIVE OBSERVATIONS ON MILK EJECTION

1958 ◽  
Vol 16 (3) ◽  
pp. 237-260 ◽  
Author(s):  
B. A. CROSS
Keyword(s):  
Spinal Cord ◽  
Mammary Gland ◽  
Spinal Anaesthesia ◽  
Dose Range ◽  
Abdominal Muscles ◽  
Mechanical Stimuli ◽  
Milk Ejection ◽  
Thoracic Spinal ◽  
Spontaneous Motility ◽  
Stimulation Of

SUMMARY The spontaneous motility of the intact uterus of spayed oestrogenized rabbits under sodium pentobarbitone anaesthesia has been recorded. Both uteri of each animal behaved similarly, and contractions often appeared to be synchronous. Small changes of load affected the amplitude of contractions, but did not alter uterine responsiveness to neurohypophysial or adrenomedullary hormones. Mid-thoracic section of the spinal cord obliterated spontaneous motility of the uterus; spinal anaesthesia did not. Spontaneous motility persisted for as long as 7 hr after decerebration and removal of the pituitary gland. The threshold dose of oxytocin for activating the oestrogenized uterus was the same as that for the lactating mammary gland, i.e. 1–5 mu. Doses up to 50 mu. usually gave an increase in frequency and amplitude of contractions. In the same dose range vasopressin either had little effect or inhibited spontaneous uterine motility, although milk ejection was stimulated. Slow infusion of oxytocin at rates of 1·5–48 mu./min produced graded increases in the rate and depth of uterine contractions and, at the same time, in similarly treated, lactating animals, rhythmic milk-ejection responses which at the higher rates of infusion merged to give a tetanic (plateau) type of milk ejection. Adrenaline or noradrenaline in doses of 1–5 μg produced diphasic uterine responses, initial contractions being followed by inhibition of spontaneous motility. They also inhibited the uterine, as well as the milk-ejection response to oxytocin injected 10–30 sec later. The inhibitory effect of adrenaline on both organs was about twice that of noradrenaline. The above-mentioned responses to adrenaline and oxytocin could also be elicited by electrical stimulation of the hypothalamus. Stimuli in the dorsal, lateral, perifornical and posterior hypothalamic areas produced effects equivalent to those of 1–5 μg adrenaline on both the uterus and mammary gland. These responses were abolished by mid-thoracic section of the spinal cord or by spinal anaesthesia. In such preparations responses typical of those produced by oxytocin were seen in both organs after stimulation of the paraventricular nuclei, supraoptic nuclei and the hypothalamo-hypophysial nerve pathways of the tuber cinereum and neural stalk. Dilatation of the vagina (or rectum) gave rise to a uterine response similar to that resulting from adrenaline or noradrenaline. The response was abolished by spinal anaesthesia, but not by mid-thoracic spinal section or decerebration. The same stimuli also produced 'bearing down' contractions of the abdominal muscles. Contractions of the uterus could also be elicited by mechanical stimuli, in the absence of functional spinal connexions.

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