Mouth and throat, face, and the five senses
Frank J. Dye in Human Life Before Birth, 2019
To perceive vibrations propagated through the air, natural selection has provided us with a high-fidelity, stereophonic receiver, comprising our ears and brain. Sound waves, gathered into our external ear canals by the pinnae, cause first our eardrums and then our middle ear ossicles to vibrate, setting in motion fluid movement in the cochlea of the inner ear. This movement causes stereocilia in the cochlea to bend, resulting in a train of nerve impulses being sent (via cranial nerve VIII) to the brain, which interprets the impulses as sound. In addition, the inner ears possess systems of semicircular canals. These canals allow us to sense our position in space, and consequently maintain balance as we go about our various activities, by detecting fluid motion in three axes (x, y, and z) (Figure 17.8).
Anatomy and Physiology of Balance
R James A England, Eamon Shamil, Rajeev Mathew, Manohar Bance, Pavol Surda, Jemy Jose, Omar Hilmi, Adam J Donne in Scott-Brown's Essential Otorhinolaryngology, 2022
The semicircular canals are orientated so that they provide complementary information about angular movement. Anti-clockwise head rotation (turning your head to the left) increases the nerve-fibre firing rate of the left lateral semicircular canal and decreases the firing rate of fibres from the right lateral semicircular canal. The perception of head rotation is the net result of differential firing rates between these complementary lateral semicircular canals (see Figure 2.4). The superior and posterior canals of opposing ears lie in the same plane. Therefore, with the head rotated 45° to right, head flexion results in an increased fibre firing rate of the right superior semicircular canal and decreased firing rate of the left posterior semicircular canal. With the head rotated 45° to right, head extension causes reversal in this pattern of activation, between the right superior and left posterior semicircular canals.
Clinical management
Alistair Burns, Michael A Horan, John E Clague, Gillian McLean in Geriatric Medicine for Old-Age Psychiatrists, 2005
The vestibular labyrinth is anatomically associated with the cochlea (which subserves hearing) in the petrous temporal bone. The components of the vestibular labyrinth are the semicircular canals, utricle and saccule. The labyrinth is fluid-filled and movements in the fluid are sensed by hair cells. The semicircular canals sense angular acceleration of the head, whereas the utricle and saccule sense linear acceleration and gravity. The three semicircular canals are at right angles to each other. The lateral canals on each side are coplanar. The anterior canal on one side is coplanar with the posterior canal on the other. Thus, for movement in any pla�e, at least two semicircular canals code the activity for the CNS responses. The sign�is from the semicircular canals cease once the head acceleration ceases. In contrast, the utricle (oriented vertically) and the saccule (oriented horizontally) have sus- tained sign�is during static head tilt with respect to gravity.
Dissociated responses to caloric and head impulse stimulation in a case of isolated vestibule-lateral semicircular canal dysplasia
Published in Acta Oto-Laryngologica Case Reports, 2018
Ricardo Wegmann-Vicuña, Octavio Garaycochea, Pablo Domínguez-Echavarri, Carlos Guajardo-Vergara, Reyes García-Eulate, Nicolás Pérez-Fernández
Spontaneous and direction fixed positional nystagmus is a very common finding in patients with chronic dizziness and in those with recurrent nonpositional vertigo spells; in the later, intensity and direction are related to the time elapsed since the last vertigo spell. It is a non-localizing finding that even during an acute crisis of Méniere’s disease is difficult to correlate with a specific peripheral vestibular deficit [9]. In our patient seen in an intercritical period late after the last vertigo spell the VEMP tests and the horizontal canals VOR gains, as measured with the vHIT, demonstrated responses within normal limits. It could be argued, thus, that it could be a manifestation of habituation once the acute dysfunction has recovered. Likewise, Yukawa et al. [10] described a case of bilateral posterior semicircular canal and lateral semicircular canal dysplasia with dilation of the vestibule on both sides and with normal cVEMP and VOR elicited by horizontal rotational stimulus, along with decreased caloric response in the same ear.
Dynamic visual acuity in benign paroxysmal positional vertigo
Published in Acta Oto-Laryngologica, 2018
Vestibulo-ocular reflex (VOR) abnormality is not expected in patients with BPPV as long as they do not have any associated inner ear problem since no organic pathology specific to BPPV is reported up to now. However, in view of recent studies, testing the VOR to understand the inner ear function and to analyze how well those patients use their vestibular function in daily life is worth to investigate. Semicircular canals react to head movements. The otolithic signal is created in response to motion, which plays an important role in perception of orientation and the direction of motion [4]. Compensatory eye movement occurs after linear acceleration of the head, opposite in direction to the head movement, and is generated to stabilize the image of the target in co-ordination with movement and balance. Thus, vision is maintained during high-velocity head motion. The impact of dysfunction on the VOR in patients with chronic vestibular problems is associated with inability to have a clear image of the target on the retina during head movements, resulting in blurred vision [4]. This condition is due to a distorted phase relationship between the eye and head movement.
Vestibular function in children with generalized epilepsy and treated with valproate
Published in Expert Review of Clinical Pharmacology, 2022
Sherifa Ahmed Hamed, Amira Mohamed Osiely
The vestibular system is divided into peripheral and central components. The peripheral component is composed of the semicircular canals, otolith (saccule and utricle) organs and the superior and inferior vestibular nerves. The central component begins from the point of entrance of vestibular nerves to the brainstem, the medial and lateral vestibular nuclei and the central inter-relations and connections to the thalamus and cerebral cortex. The semicircular canals sense horizontal angular head accelerations. Their afferents project to the medial vestibular nuclei via the vestibulo-ocular reflex (VOR). They provide reflexive ocular motor responses for maintenance of gaze stability. The otolith organs sense linear acceleration and static tilt in relation to gravity. Their afferents project to the lateral vestibular nucleus via the vestibulo-spinal reflex (VSR) for postural control and via connections to the cerebellar neurons, thalamus, and higher-cortical areas for balance, self-motion, and gravity direction [14].
Related Knowledge Centers
- Bony Labyrinth
- Endolymph
- Inner Ear
- Membranous Labyrinth
- Perilymph
- Petrous Part of The Temporal Bone
- Temporal Bone
- Periosteum
- Ear
- Petrous Part of The Temporal Bone
- Sense