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10.8

10.8. Sense of equilibrium . Intro. Two senses of equilibrium - Static equilibrium: the maintenance of balance when the head and body are motionless. - Dynamic equilibrium: maintenance of balance when the head and body are suddenly moved or rotated. Static Equilibrium. Key terms

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10.8

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  1. 10.8 Sense of equilibrium

  2. Intro • Two senses of equilibrium - Static equilibrium: the maintenance of balance when the head and body are motionless. - Dynamic equilibrium: maintenance of balance when the head and body are suddenly moved or rotated.

  3. Static Equilibrium • Key terms • vestibule: a bony chamber between the semicircular canals and the cochlea. • utricle: an enlarged portion of the membranous labyrinth of the inner ear. • saccule: an enlarged region of the membranous labyrinth of the inner ear. • macula: has many hair cells, which serve as sensory receptors.

  4. Static Equilibrium • The process of static equilibrium. • The organs of static equilibrium are located within the vestibule and contain two expanded chambers – utricle and saccule. They each have a tiny structure called a macula. • The nerve impulses travel into the CNS on the vestibulocochlear nerve, informing the brain of the head’s new position. The brain sends motor impulses to skeletal muscles, which contract or relax to maintain balance.

  5. When the head is upright, the hairs of the hair cells project upward into a mass of gelatinous material, which has grains of calcium carbonate embedded in it. The head bending forward, backward, or to one side stimulates hair cells, and they signal the nerve fibers associated with them.

  6. Dynamic Equilibrium • Key terms • ampulla: houses the sensory organs of the semicircular canals. • cristaampularis: contains a number of sensory hair cells and supporting cells. • cupula: dome-shaped gelatinous mass.

  7. Dynamic Equilibrium • The process of dynamic equilibrium • rapid turns of the head/body simulate the hair cells of the cristaampullaris, causing the semicircular canals to move with the head or body, but the fluid inside the membranous canals remain stationary. • this bends the cupula in one or more of the canals in a direction opposite that of the head/body movement

  8. Summary • Static equilibrium maintains the stability of the head and body when they are motionless. • Dynamic equilibrium balances the head and body when they are moved or rotated suddenly; other structures that help maintain equilibrium include the eyes and mechanoreceptors associated with certain joints.

  9. Tehiind. ;D

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