Nature has given us certain sensors which are spread in different parts of the body. These sensors pick up the information and constantly inform the brain about the stability of the ground and the surroundings via afferent neural pathway.
The information coming from the eyes, skin, muscle and joints is integrated with the information coming from the inner ears and processed in the brain. Central processing of information in the brain is essential for balance.
—> In response the brain evolves a motor output via efferent nerves– thereby creating a precise and timed contraction of different body muscles to restore the stability.
—> Resulting in movement of head and neck, legs, eyes and rest of the body to maintain the balance and have clear vision while person is moving
Thus Maintenance of balance is a reflex action with the involvement of a sensory organ, an afferent neural pathway, a center of the reflex in the brain stem, an efferent neural pathway and an effector motor organ.
Afferent sensory organs–
- Eyes – Inform brain about our position and movement.
- Proprioceptors–Skin, muscles and joints inform the positions of our arms, legs, and other parts of body.
- Inner Ear Vestibular organs –Movement & position of head
Center of the reflex—
Situated in the brain-stem where 4 vestibular nuclei are present
Efferent neural pathway –
Neural tracts in the brain and spinal cord and peripheral nerves
Effector motor organ–
Different muscles of the body
Skeletal Muscles of the limb, trunk and neck (Vestibulo-spinal pathway)—vestibulospinal reflex —
Small Muscles of the eye Vestibulo ocular reflex pathway
Hence in order to have a properly working balance system we basically need:–
A perfectly working vestibulo spinal reflex system
A perfectly working vestibulo ocular system
A very good cerebellar system
For good balance eyes, nerve signals from the skin muscles and joints, and inner ears should work normally.
However, if we shut our eyes, we still have a good sense of balance because of the signal from inner ears, and other parts of our body
Role of Ear—
The labyrinth of the inner ear is composed of the vestibule (utricle and saccule) and the 3 semicircular canals. These are–
- The vestibular labyrinth is made up of three semicircular canals (lateral, posterior and superior) at right angles to each other and joining together at the vestibule (Utricle and Sacule).
- filled with fluid called endolymph and have receptors to inform the brain about the head’s position in space
- Semicircular canals detect direction of gravity and detect and measure movements and acceleration in all three planes of space.
- The right and left balance organs work together, constantly sending signals via the audiovestibular nerves to the brain, about position and direction of movement.
Vertigo is caused by conflict of information between inner ear and other sensory system or defect in central integration of vesitbular information in brain.