Question

Explain how “tiny rocks in your head” help your balance when your head is tilted forward, back, and side-to-side

Answer 1

The balance of head with respect to its body is governed by vestibular system which lies within inner ear.The two main components of the vestibular system are (1) the peripheral vestibular component and (2) the central vestibular component.

The peripheral vestibular component consists of three semicircular canals, two otolithic organs, and cranial nerve VIII. Semicircular canals detect the rotational movements of the head. For example, the semicircular canals are activated when you turn your head left and right or when you tilt your head up and down. When a rotational head movement occurs, it causes the fluid in the semicircular canals to move. The movement of the fluid causes hair cells in the semicircular canals to bend, and the bending of the hair cells stimulates cranial nerve VIII.The two otolithic organs are the utricle and the saccule. The purpose of the otolithic organs is to detect linear movements of the head. The otolithic organs are able to respond to linear head movements (forward & backward) in the following way. When a linear head movement occurs, it causes the fluid in the otolithic organs to move but otoconia in the otolithic organs to lag behind. The lagging behind of the otoconia causes hair cells in the otolithic organs to bend, and the bending of the hair cells stimulates cranial nerve VIII.Cranial nerve VIII is comprised of the cochlear nerve (for hearing) and the vestibular nerve (for balance). The purpose of the vestibular nerve is to transmit balance-related information from the semicircular canals and the otolithic organs to the central nervous system.

The central nervous system is composed of the vestibular nuclei, the ascending tract, and the descending tract.Once the vestibular nuclear complex has made sense of all of this incoming information, it transmits outgoing information along the ascending tract to control the movement of the eyes and along the descending tract to control the movement of the muscles. The eyes are primarily stabilized through a mechanism known as the vestibulo-ocular reflex (VOR), and the body is primarily stabilized through a mechanism known as the vestibulo-spinal reflex (VSR).