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Saliva, Swallowing, and Lower Oesophageal Sphincter
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Swallowing is a complex reflex controlled by the swallowing centre in the medulla oblongata, which transfers food from the oral cavity to the stomach. Swallowing occurs in three phases (Figure 33.1): an initial voluntary oral phase, which is followed by involuntary pharyngeal and oesophageal phases coordinated by the swallowing centre in the medulla and pons.
Traumatic Carotid Sinus Reflex
Published in Burkhard Madea, Asphyxiation, Suffocation,and Neck Pressure Deaths, 2020
Elke Doberentz, Burkhard Madea
Of high forensic interest is the carotid sinus, which is located in the medial vessel wall of the internal carotid artery in the area of the carotid bifurcation. The carotid sinus consists of baroreceptors (stretch-sensitive fibres), which are located in the adventitia as small bundles of nerve fibres (Figure 25.4). They are in contact with elastic fibres of the vessel wall [4,22]. The carotid sinus is stimulated by elongation and deformation of the carotid wall, especially in response to rapidly increasing blood pressure (rise of intravascular pressure) and also external pressure. By rapid and powerful reflex stimulation of the parasympathetic area of the medulla oblongata and an inhibition of sympathetic areas, this induces a decrease in heart rate (bradycardia) and in blood pressure (hypotonia) and the reduction of the peripheral vessel tone (vasodilatation) [7]. Alterations in an electrocardiogram occur after a few seconds after stimulus onset [7,3,8]. In contrast, the compression of the common carotid artery beneath the carotid bifurcation is accompanied by an acute reduction of vascular pressure due to decreased blood flow. This induces tachycardia, tachypnoea and the release of catecholamines [18]. The faster the pressure changes, the more intense the reactions are.
Role of central GABA in the regulation of blood pressure and the development of hypertension in the SHR
Published in H. Saito, Y. Yamori, M. Minami, S.H. Parvez, New Advances in SHR Research –, 2020
Maarten Van Den Buuse, Geoffrey A. Head
Modulation of GABAergic systems in other regions of the medulla oblongata also induced changes in blood pressure. Thus, micro-injection of muscimol into the dorsal raphe nucleus caused a reduction of both blood pressure and heart rate (Robinson et al., 1986). Micro-injection of bicuculline into the nucleus ambiguus similarly caused a decrease in blood pressure and a marked bradycardia (DiMicco et al., 1979). Such an effect was not observed after micro-injection into the other brainstem regions, such as the NTS or DMX. Injection of muscimol into the nucleus ambiguus inhibited bradycardic responses to intravenous phenylephrine injections (Williford et al., 1980b), indicating that this nucleus is one of the sites in the brain where GABAergic drugs may influence vagal reflexes. Finally, intrathecal injection of muscimol decreased blood pressure, heart rate, and sympathetic nerve activity, while intrathecal injections of bicuculline had the opposite effect (Gordon, 1985).
Baroreflex control model for cardiovascular system subjected to postural changes under normal and orthostatic conditions
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
V. L. Resmi, R. G. Sriya, N. Selvaganesan
On changing the position from supine to standing, blood pools towards the lower body due to gravity, which changes the distribution of the blood volume in the body, leading to change in venous pressure. The rapid blood pressure change is sensed by detecting the level of tension on vascular walls with the help of baroreceptors located in the carotid sinus and arch of the aorta. The Baroreceptors fire action potentials according to the blood pressure sensed through mechano-electrical transduction to the central nervous system. This information is processed in the medulla oblongata and its cardioinhibitory and vasomotor centers then create sympathetic and parasympathetic nerve activities, respectively (Solaro et al. 2019). The efferent pathways transmit these activities in the form of impulses to the various parts of the cardiovascular system which affects the blood pressure by changing the peripheral resistance, compliance, stroke volume and contractility.
Botulinum toxin A injection using ultrasound combined with balloon guidance for the treatment of cricopharyngeal dysphagia: analysis of 21 cases
Published in Scandinavian Journal of Gastroenterology, 2022
Lielie Zhu, Jiajun Chen, Xiangzhi Shao, Xinyu Pu, Jinyihui Zheng, Jiacheng Zhang, Xinming Wu, Dengchong Wu
As part of the upper oesophageal sphincter (UES), normally, the cricopharyngeal muscle maintains tension and contraction during breathing, preventing air from entering the oesophagus and protecting the airway from retrograde reflux from the stomach [1–3]. During swallowing, food is pushed from the mouth to the pharynx under the contraction of masticatory muscles, tongue muscles and pharyngeal muscles; then, the hyoid–laryngeal complex moves upwards and forwards, and the cricopharyngeal muscle relaxes physiologically to allow food to pass through [38]. This swallowing motor sequence is regulated by the medulla oblongata swallowing central pattern generator (CPG) [39]. Brain lesions of many causes, especially brainstem stroke, could damage this regulatory mechanism, which then cannot distribute the swallowing impulse to the relevant motor nucleus, resulting in cricopharyngeal muscle achalasia [38,39]. Therefore, patients with stroke were selected as the participants in this study, which has important clinical significance because of its high incidence and the high incidence of cricopharyngeal muscle achalasia after stroke [5–7,23]. In addition, with good administration, stroke can reach a relatively stable clinical state compared with other progressive neurogenic or neuromuscular diseases, which might hinder patients from gaining permanent therapeutic effects.
The evolution of the concept of synesthesia in the nineteenth century as revealed through the history of its name
Published in Journal of the History of the Neurosciences, 2020
Jörg Jewanski, Julia Simner, Sean A. Day, Nicolas Rothen, Jamie Ward
In the year of Chabalier’s article, 1864, the term synesthésie was used by the famous French physiologist (Edmé Félix) Alfred Vulpian (1826–1887). He inserted it in a public lecture at the end of his 20th Lecon sur la physiologie, dated July 21, and published these lectures two years later (1866, 465; cf. Schrader 1969, 46–49). But Vulpian’s understanding of synesthesia was different from ours today. He used it specifically for phenomena linking touch or light to coughing or sneezing (see below), which he related to the tail of the medulla oblongata (in the brainstem) in particular. It certainly had no links at that time to hyperchromatopsie or pseudochromesthésie in this context: Mechanical irritation of the external auditory canal gives rise to a special sensation, a tickling in the throat, that makes people cough. The impression on the eyes of a bright light, sunlight for example, causes a particular tickle in the mucus membrane in the nasal cavity and indirectly provokes a fit of sneezing in certain susceptible people. … It’s via the terms sympathy [original: sympathie] or synesthesia [original: synesthésie] that we must designate the phenomena in question. Or even, with Müller, we could use the expression associated sensations [original: sensations associées]. (Vulpian 1866, 463 and 465)