Comparative Anatomy and Physiology of the Mammalian Eye
David W. Hobson in Dermal and Ocular Toxicology, 2020
The musculature of the eyelids includes the muscles which close the eye, the orbicularis oculi, and those that open the eye, the levator palpebrae being the major muscle. A smooth muscle (Muller’s muscle) is found deep, extending along the course of the levator. It is under adrenergic innervation and results in a widened palpebral margin when stimulated. The orbicularis muscle fibers are arranged in bundles parallel to the free lid margin. The muscle is restricted in its circular sphincter action by restrictions in the nasal and temporal extremities. A firm attachment is accomplished by the medial palpebral ligament in all animals except the primate, which has a common tendon of the superficial heads of the pretarsal orbicularis oculi that inserts in the medial orbital wall. On the temporal side, the common tendon of the temporal pretarsal orbital axis assumes the function of the lateral ligament in primates, while in the other animals it is the retractor anguli muscle which serves this function. These structures allow the lid to close from laterally to medially, propelling tears to the medial aspect where the lacrimal puncta are found. The innervation to the eyelids includes sensory, motor, and autonomic portions. The sensory to the upper lid is the frontal branch of the ophthalmic division of the fifth cranial nerve, while the lower is the maxillary division of the fifth cranial nerve. Motor innervation is provided by the third (levator) and seventh (orbicularis) cranial nerves. The autonomic innervation is sympathetic to Muller’s and the smooth muscle of the third eyelid.
Peripheral Autonomic Neuropathies
David Robertson, Italo Biaggioni in Disorders of the Autonomic Nervous System, 2019
Autonomic dysfunction can also manifest with positive phenomena. In tetanus, for example, hyperhidrosis accompanies hypertension with tachycardia and, in autonomic hyperreflexia due to spinal cord transection, bouts of hypertension, sweating, bradycardia, pupillary changes and outpouring of catecholamines occur in response to stimuli of bladder filling stretch or peristaltic movements. Alternatively, autonomic paralysis may be associated with compensatory hyperactivity in normally innervated areas; for example, facial hyperhidrosis in patients with diabetic neuropathy and the segmental hyperhidrosis in partial peripheral nerve injuries. Autonomic function may be impaired in the paraspinous area when lung tumours invade the pleura, but hyperhidrosis occurs in such areas associated with tumour invasion of intercostal nerves.
Influence of Autonomic Nerves on Lymph Flow
Waldemar L. Olszewski in Lymph Stasis: Pathophysiology, Diagnosis and Treatment, 2019
The foregoing evidence makes it clear that lymphatic vessels possess a sympathetic motor innervation. The question naturally arises as to what is the function of such an innervation in the living animal. Thornbury64 examined the possibility that lymphomotor reflexes might be activated during baroreceptor or volume receptor responses. He found that a 5 min bilateral occlusion caused a 20 to 30 mm rise in arterial pressure (top record in Figure 19) but had little effect on lymph flow (second record from bottom) although there was a slight increase in lymphatic frequency (bottom record). Raising intrathoracic pressure was likewise without effect on lymph flow (see Figure 20) either at onset (when arterial pressure fell) or on removal of the stimulus (when arterial pressure transiently increased). These results would suggest that the lymphatic system does not participate in reflexes initiated at pressoreceptors. There are, however, good reasons to believe that such a conclusion is not fully warranted since such reflexes are difficult to demonstrate in anesthetized animals. For example, in cats halothane almost totally abolished the pressor response to carotid occlusion,65 while in dogs there was a greater than 50% reduction in the response to carotid sinus hypotension.66 Barbiturate anesthesia caused a 60% depression of the response to carotid occlusion in dogs,66 and in man abolished the vasomotor response to hypotension during lung inflation.67
A computational model of upper airway respiratory function with muscular coupling
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Olusegun J. Ilegbusi, Don Nadun S. Kuruppumullage, Matthew Schiefer, Kingman P. Strohl
For the genioglossus (the major upper airway dilator muscle), we assumed that muscle contraction occurred for 3s along an anterior-posterior direction. The strength of the contraction was induced through a time-force function in the FE model. In reality, the contraction of muscle tissues is activated through impulses delivered through the motor nerve network, for instance, the hypoglossal nerve for genioglossus in the tongue (Eisele et al. 1997; Yoo and Durand 2005). Figure 3 shows the activation profile used in this study. The activation duration was chosen to mirror a typical neurostimulation procedure. The magnitude of the force at this stage was chosen through preliminary simulations with varying forces until a profile produced airway openings at the epiglottis level typically observed in trial applications of neurostimulation. The activation profile was used as a distributed load within the region of genioglossus muscle. We assumed the airway structure was initially at rest. Therefore, there was no activation for the first 3s of the simulation in order to allow the airway structure to reach stable condition under gravity in the lateral-posterior direction.
Habitual use of psychological coping strategies is associated with physiological stress responding during negative memory recollection in humans
Published in Stress, 2022
The hypothesis that the average SCL trajectory would follow an upside-down u-shaped curve was not supported. The average trajectory of SCL showed the opposite pattern, indicating that the SNS did not, on average, innervate the eccrine sweat glands in preparation for fight-or-flight responding. Mean decreases in SCL are observed during some tasks, such as a mirror-tracing task (El-Sheikh et al., 2010); the increases in SCL following the 3-min mark observed in this study may indicate recovery. Rather than fight-or-flight responses, decreases in SCL may represent engagement responses (Porges, 2007). Lower SNS innervation of various target organs promotes calm and allows physiological resources to be devoted to attending to social cues, adjusting behavior to meet social expectations, and negotiating complex relationships with others. The decreases in SCL at the beginning of the interview may therefore permit recall and sharing of a negative autobiographical memory with the experimenter. Measurement of autonomic innervation of other target organs is needed to further investigate this possibility.
Changes in Corneal Subbasal Nerves after Punctal Occlusion in Dry Eye Disease
Published in Current Eye Research, 2021
Golshan Latifi, Ali Banafshe Afshan, Amir Houshang Beheshtnejad, Mehran Zarei-Ghanavati, Neda Mohammadi, Reza Ghaffari, Hamed Ghassemi, S.Saeed Mohammadi, Ahmad Kheirkhah
Dry eye disease (DED), one of the most common disorders of the ocular surface, is caused by disruption of homeostasis of the tear film resulting in symptoms of visual disturbances, redness, irritation, and foreign body sensation.1,2 Corneal nerves are critical for the maintenance of the ocular surface health; they also play an important role in the pathogenesis of DED.3,4 The cornea is supplied by sensory divisions of the ophthalmic branch of the trigeminal nerve. In addition to sensory function, this rich innervation helps maintain integrity of the epithelium and wound healing through trophic functions of the nerves.5,6 Tear secretion is also mainly modulated through corneal sensory nerves as a reflex mechanism and any impairment in innervation of the cornea causes less tear production.7