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Drawing of the statocyst system Statocysts (ss) and statolith (sl) inside the head of sea snail Gigantopelta chessoia. The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, [1] cnidarians, [2] ctenophorans, [3] echinoderms, [4] cephalopods, [5] [6] crustaceans, [7] and gastropods, [8] A similar structure is also found in Xenoturbella. [9]
The utricle and saccule are part of the balancing system (membranous labyrinth) in the vestibule of the bony labyrinth (small oval chamber). [1] They use small stones and a viscous fluid to stimulate hair cells to detect motion and orientation. The utricle detects linear accelerations and head-tilts in the horizontal plane.
The calcium carbonate that the otolith is composed of is primarily derived from the water. As the otolith grows, new calcium carbonate crystals form. As with any crystal structure, lattice vacancies will exist during crystal formation allowing trace elements from the water to bind with the otolith.
Otoconia are crystals of calcium carbonate and make the otolithic membrane heavier than the structures and fluids surrounding it. [1] The otoconia are composite crystallites that overlie the macular sensory epithelium of the gravity receptors of most vertebrates and are required for optimal stimulus input of linear acceleration and gravity. [3]
Balance skill development in children Balance training using medicine balls The sense of balance or equilibrioception is the perception of balance and spatial orientation . [ 1 ] It helps prevent humans and nonhuman animals from falling over when standing or moving.
A woman demonstrating the ability to balance A waiter balancing wine glasses. Balance in biomechanics, is an ability to maintain the line of gravity (vertical line from centre of mass) of a body within the base of support with minimal postural sway. [1] Sway is the horizontal movement of the centre of gravity even when a person is standing still.
Problems with balance can occur when there is a disruption in any of the vestibular, visual, or proprioceptive systems. Abnormalities in balance function may indicate a wide range of pathologies from causes like inner ear disorders, low blood pressure, brain tumors, and brain injury including stroke. [citation needed]
Depending on the symmetry of a crystal structure (as determined by one of the 32 possible crystallographic point groups), crystals in that group may be forced to be isotropic (not birefringent), to have uniaxial symmetry, or neither in which case it is a biaxial crystal. The crystal structures permitting uniaxial and biaxial birefringence are ...