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Equilibrium I & II

Equilibrium I & II. Prof.Lammers Unit 8/ Week 5-6. R.E.B, Equilibrium . 4medstudents.com 2003. The Vestibular System. The Visual System. The Propreceptive System. Systems involved in Equilibrium. The main systems that are involved in equilibrium are:. Cerebellum. Vestibular System.

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Equilibrium I & II

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  1. Equilibrium I & II Prof.Lammers Unit 8/ Week 5-6 R.E.B, Equilibrium. 4medstudents.com 2003

  2. The Vestibular System The Visual System The Propreceptive System Systems involved in Equilibrium • The main systems that are involved in equilibrium are: Cerebellum

  3. Vestibular System • The vestibular apparatus is located in the inner ear and comprises of 3 semi-circular canals and vestibule which contain these sensor organs: • The utricle • The saccule • 3 ampulla • These organs contain the sensory hair receptors: • the maculae (for the utricle & saccule) • and cristae (ampullae).

  4. Types of Equilibrium • Static equilibrium: is concerned with the orientation of the body relative to the ground ( Linear acceleration) • Dynamic equilibrium is concerned with the maintenance of posture, especially in the head ( Rotational movement) Rotational movement

  5. 1. Static Equilibrium • Receptors for static Equilibrium are the maculae. • Each maculae conations supporting cells and scattered receptors called hair cells • Each of the hair cells has a major process called a kinocilium and several smaller stereocilia. Lying over the supporting and hair cells is a gelatin-like otolithic membrane. This membrane slides over the hair cells and stimulates them when the head is moved.

  6. 1- Supporting cells 4- Membrane otolithique 2- Hair cell 5- nerve fibers 3- Cilia 6- Otolithes

  7. Saccule Utricle Static Equilibrium • The Maculae are responsible for linear acceleration forces. • The Maculae are in the • Saccule : is responsible for vertical acceleration • Utricle: Is responsible for horizontal acceleration Maculae in Saccule & utricle

  8. Linear Acceleration Stimuli • When the head starts or stops moving in a linear acceleration otolothic membrane slides backward or forward over hair cells the hair cells will bend

  9. Linear Acceleration Stimuli • When the hair bends towards the kinocilium the hair cell depolarize faster steam of impulse is sent to the brain • When the hair bends in the opposite direction the hair cells hyperpolarize Slower impulse generation NOTE: It is important to understand that the maculae is responsible for the change in acceleration only. Because the hair cell can adapt it quickly Nerve Action Potential

  10. Dynamic Equilibrium • The receptors for Dynamic equilibrium are the ampulla which is found in the semicircular canals. • In each ampulla is a small elevation called a crista. Each crista is made up of hair (receptor) cells and supporting cells, and covered by a jelly-like material known as the cupola. Movement of the cupola stimulates the hair cells Ampulla

  11. Ampulla

  12. Dynamic Equilibrium • The ampulla is responsible for the change in rotational movement, as continuous rotation does not stimulate the ampulla. • when the head starts moving in a rotationally the endolymph in the semicircular ducts move in the direction opposite to the body’s direction deforming the crista in the duct causes depolarization • If the body continues to rotate at a constant rate The endolymph moves at the same direction and speed as the body and stop the movement of hair cells

  13. Dynamic Equilibrium • When we suddenly stop moving, the endolymph keeps on moving in the opposite direction hyperpolarization of the hair cells that will tell the brain that we have stopped movement.

  14. The Visual System • The 2nd system that plays an important role in equilibrium is the visual system. • The effect of the visual system is best noticed when there is a conflict between the messages that reach the brain. • Motion sickness is a very common equilibrium disorder in which is due to sensory input mismatch. The main symptoms are: Nausea, dizziness, vomiting and pale appearance

  15. Motion sickness • Ex. of motion sickness: • When we read while traveling, the visual inputs indicates that the body is fixed. But as the vehicle is moving the vestibular system detects movement and send impulses that conflict with the visual system. • The Brain receives conflicting information which will lead to motion sickness.

  16. Propreceptive system • Nerve endings that respond to muscle and tendon stretch are called propreceptors (ex. Muscle spindle). They send signals to the brain, giving it information about the posture of the body. • The proprioceptors are available in the muscles, ligaments, tendons, and joints. It which they can detect the initiation and termination of body movement. • Note: In a sitting situation the system that is responsible for equilibrium in the PRORIORECEPTOR

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