Describe how the inner ear anatomy leads to nystagmus; what is the physiological

Vestibular nystagmus occurs during self-rotation even in darkness: the inner ear contains motion detectors (vestibular labyrinth) which project to the vestibular nuclei and cerebellum. A vestibular nystagmus can also be induced by irrigating the ears with warm or cold water. With unilateral irrigation the conjugate nystagmus is horizontal, torsional or oblique, depending on the position of the head. Both a convection mechanism and a direct temperature effect on the canal's sensory apparatus have been proposed to account for the involuntary oscillations.

Diseases affecting the visual system, such as retinal disorders causing visual loss, commonly lead to nystagmus because visual fixation is no longer possible. Disease affecting the vestibular organ in the inner ear causes an imbalance that leads to a mixed horizontal—torsional nystagmus, usually associated with vertigo. Disease affecting the central connections of the vestibular system, including the cerebellum, may cause several forms of nystagmus. These include down-beat, torsional, periodic alternating and see-saw nystagmus. None of these nystagmus types are, in themselves, pathognomonic of central nervous system disease. Nonetheless, down-beat nystagmus is usually associated with lesions of the vestibulo-cerebellum (flocculus, paraflocculus, nodulus and uvula) and the underlying medulla; up-beat nystagmus is most commonly reported with lesions of the medulla, including the perihypoglossal nuclei and adjacent vestibular nucleus (both structures are important for gaze-holding), the ventral tegmentum and the anterior vermis of the cerebellum; periodic alternating nystagmus is often linked to cerebellar disease (note that in this case the horizontal jerk nystagmus spontaneously reverses direction of the quick phase every few seconds); see-saw nystagmus is linked to parasellar lesions of the optic chiasm (e.g. pituitary tumours) and achiasma (note that this is a rare form of pendular nystagmus in which the torsional components are conjugate and the vertical components are disjunctive—one eye rises and intorts while the other falls and extorts); and gaze evoked nystagmus is commonly seen as a side-effect of drugs, including sedatives, anticonvulsants and alcohol, as well as cerebellar disease

nystagmus is basically when the eye jumps as you turn your head, instead of moving with your head and blurring your vision your eye stays put and then jumps to where you turned your head to. So the purpose of it is to ensure your vision doesn't blur, because blurry vision is no good to your brain.

so how does this occur? so in the inner ear there are the semicircular canals. In these canals there is a watery substance that moves hair cells in the inner ear. Without getting too complicated, when you turn your head the watery substance moves and knocks into the hair cells and activates medial vestibulospinal tract. Which controls involuntary eye movement and other things that's not important.

SUMMARY: caused by movement of the watery stuff in your ear which knocks into hair cells and causes the eye to move a certain way. Nystagmus is named by the direction it jumps, so right nystagmus you turn your head right. anyway, the purpose of it is to stop visual blurring when you turn your head.