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Special Considerations in Gaze
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Mohamed Elkasaby, Aasef G. Shaikh
The EBNs driving horizontal saccades are in a different mesencephalic nucleus compared to vertical EBNs [45–47]. Horizontal EBNs are in the paramedian pontine reticular formation while rostral interstitious nucleus of medial longitudinal fasciculus has vertical EBNs [48]. The EBNs are only active during saccades; their discharge rate determines saccade velocity [46–48]. The IBNs are connected with the EBNs; but in addition, IBNs project across the midline mutually inhibiting each other. Such mutually reciprocal inhibition is critical for generating post-inhibitory rebound, a mechanism critical for sufficient strength of burst ensuring rapid saccade velocity.
Cranial Neuropathies I, V, and VII–XII
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
From the gasserian ganglion, sensory fibers enter the pons and terminate on the three sensory nuclei. The principal sensory nucleus mediates pressure and light touch from the face and oral cavity and contains second-order neurons that project to the ipsilateral and contralateral ventral posteromedial (VPM) nuclei of the thalamus via the dorsal trigeminothalamic tract (Figure 21.6). The spinal trigeminal tract and nucleus mediate pain and temperature from V1 to V3. Fibers in the spinal trigeminal tract descend from the pontomedullary junction to the C2–C4 level of the spinal cord; second-order neurons project to the contralateral VPM nucleus via the ventral trigeminothalamic tract.19 The mesencephalic nucleus, which is located at the midbrain–pontine junction, contains first-order neurons that receive proprioceptive input from V3.20 This nucleus also provides the afferent limb of the jaw jerk reflex. After the trigeminothalamic tracts synapse in the thalamus, third-order neurons from the thalamus project on the somatosensory cortex.
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
The oral cavity is functionally responsible for mastication, which is the initial phase of digestion. Food is broken into smaller particles and mixed with saliva so as to soften and form a bolus for swallowing. The tongue and the cheek muscles keep the bolus between the masticatory surfaces of the teeth. The process of mastication is controlled by a reflex involving the trigeminal mesencephalic nucleus. The presence of a bolus of food in the mouth reflexly inhibits the masticatory muscles, which allows the lower jaw to drop suddenly. This, in turn, initiates a stretch reflex of the jaw muscles and a rebound contraction, which raises the jaw to compress the teeth. Usually, mastication occurs subconsciously, but it may be subject to cortical control.
Cardiovascular responses induced by the activation of muscarinic receptors of the pedunculopontine tegmental nucleus in anesthetized rats
Published in Clinical and Experimental Hypertension, 2022
Vida Alikhani, Tahereh Nikyar, Reza Mohebbati, Mohammad Naser Shafei, Atiyeh Ghorbani
The nucleus of pedunculopontine tegmentum (PPT) is a mesencephalic nucleus with multiple functions including gait and motor control(1), sleeping (2), learning and memory (3), and the control of autonomic responses including cardiovascular regulation (4,5).