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Control of Ventilation
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
There are three types of receptors in the lungs. Two types, the slowly adapting pulmonary stretch receptors and the rapidly adapting (irritant) receptors, send nerve impulses to the brain in myelinated nerve fibres in the vagi, while the third, C-fibres, send information in unmyelinated fibres. Slow adapting pulmonary stretch receptors. The slow adapting fibres of the Hering–Breuer reflexes are located in the smooth muscles of the trachea and bronchi. In the Hering–Breuer inflation reflex, the stretch receptors of these muscles during steady inflation of the lung are activated and results in an increase in the duration of expiration. A Hering–Breuer deflation reflex results in a decrease in the duration of expiration produced by marked deflation of the lung.Rapidly adapting stretch receptors. The rapidly adapting stretch receptors are found in the epithelial cells of large airways such as the carina. They increase their firing rate in response to the rate of change in lung volume and cause rapid shallow breathing. They were formerly known as irritant receptors because they respond to chemical stimuli such as cigarette smoke. The sigh or augmented breath we take every 15 minutes originates from the rapidly adapting receptors stimulated by atelectasis. This action is implicated in the first few breaths of the newborn.
Mechanically Induced Periarticular and Neuromuscular Problems
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
The concept that the primary function of ligaments is to restrain the extremes of joint motion is inconsistent with good engineering design principles. The frequency of ligamentous rupture eloquently demonstrates that ligaments are poorly constructed for this function. In dynamic circumstances, when forces are high, what limits extreme joint motion is muscular action. In passive circumstances, when the forces are low (7), the ligaments can effectively act as checks. Ligaments have an equally important function as proprioceptive receptors (8). Stretch receptors in ligaments provide necessary afferent signals to the involuntary neurological pathways to regulate appropriate antagonistic muscle contraction, which can control and limit joint motion (see Chap. 9). This system is made inoperative when the deforming forces are unexpected and there is inadequate time to “get ready”—to set preprogrammed muscular action into play. Under these circumstances ligaments rupture (9).
The circulatory system
Published in Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella, Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella
The baroreceptors respond to stretch or distension of the blood vessel walls. Therefore, they are also referred to as stretch receptors. A change in blood pressure will elicit the baroreceptor reflex, which involves negative feedback responses that return the blood pressure to normal (see Figure 6.6). For example, an increase in blood pressure causes distension of the aorta and the carotid arteries, which stimulates the baroreceptors and there is an increase in the number of afferent nerve impulses transmitted from these receptors to the vasomotor center. The vasomotor center processes this information and adjusts the activity of the autonomic nervous system accordingly. Sympathetic stimulation of vascular smooth muscle and cardiac muscle is decreased. Parasympathetic stimulation of cardiac muscle is increased. Thus, VR, CO, and TPR all decrease so that MAP is decreased back toward its normal value.
Classifier for the functional state of the respiratory system via descriptors determined by using multimodal technology
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Sergey Alekseevich Filist, Riad Taha Al-kasasbeh, Olga Vladimirovna Shatalova, Altyn Amanzholovna Aikeyeva, Osama M. Al-Habahbeh, Mahdi Salman Alshamasin, Korenevskiy Nikolay Alekseevich, Mohammad Khrisat, Maksim Borisovich Myasnyankin, Maksim Ilyash
HF-waves are presented in the ECS spectrum by one peak in the range of 0.2 to 0.3 Hz. The presence of these waves determines the RS, and their peak in the spectral region, as a rule, coincides with the RR. RR cardiac rate modulation has not been completely deciphered. There are a number of hypotheses to explain this process. The most famous of them associate this modulation with the influence of lung stretch receptors on the sinus node, with control signals from the central nervous system, with mechanisms for regulating blood pressure, and changes in the gas composition of the blood during respiration. In all cases, there are phenomena in which the modulation of the RR cardiac rhythm does not fit into the hypotheses put forward. The researchers also draw attention to the possibility of the appearance of peaks in the HF spectrum that are not associated with RRs.
Upper eyelid weighting for lagophthalmos results in contralateral upper eyelid elevation
Published in Orbit, 2022
Justin N. Karlin, Christina Le, Daniel B. Rootman
Eyelid weighting has been shown clinically and experimentally to lower the weighted eyelid,9 however the effect of weighting on the contralateral eyelid height is poorly understood. A phenomenon well known to ophthalmologists, coordinated neural control of extraocular muscles during conjugate eye movement, also known as Hering’s law of equal innervation, has been shown to apply to levator palpebrae muscles in the setting of ptosis, but has not been examined in the setting of lagophthalmos. One may hypothesize that the increased muscle tension sensed by theoretical stretch receptors of the levator muscle after upper eyelid loading may affect neural output to the contralateral levator muscle. In this study, we investigate the effect of upper eyelid loading on ipsilateral and contralateral static upper eyelid position.
Contralateral eyelid elevation following unilateral upper eyelid retraction repair
Published in Orbit, 2022
Michael B. Wong, Robi N. Maamari, Steven M. Couch
This study identifies an observed elevation in the upper eyelid position of a significant number of patients following unilateral retraction repair performed on the contralateral eyelid. Though this clinical trend highlights the impact of Hering’s law as classically described in unilateral ptosis surgery, the key differentiating feature in the present study is the activation of afferent drive following recession surgery resulting in contralateral elevation. In contrast, unilateral ptosis repair leads to a loss in afferent drive by the ptotic eye after repair, corresponding to the contralateral ptosis. The observations in the present study demonstrate the clinical impact of afferent and efferent drive, a concept with several proposed theories to describe the underlying mechanism including proprioception, mechanical stretch receptors, and neurologic feedback.6,9–11