1. Animals have specialized neurons that detect the motion of the head as it mov

Question

1. Animals have specialized neurons that detect the motion of the head as it moves through space. These mechanoreceptors are organized as neuroepithelia within the left and right vestibular:

apparatus

ganglia

nuclei

2. Rotational acceleration/deceleration of the head – as described by roll, pitch, and yaw – is detected by:

fluid-filled semicircular canals

the ampullae of the semicircular canals

otolith organs

3. Linear acceleration/deceleration of the head as well as the effect of gravity are detected by:

the semicircular canals

the ampullae of the semicircular canals

otolith organs

4. Balance requires the central integration of raw and processed sensory streams. Such integration occurs within the:

sensory cortex

cerebellar cortex

brainstem

5. The processed sensory stream that enables balance passes through one pair of peduncles. Which pair?

superior

middle

inferior

6. What do cerebellar neurons evaluate?

intent

body status

head status

all of the above

Explanation / Answer

1. Vestibular apparatus

The overall body posture and movement is balanced by the integration of information received from the vestibular system (vestibule receptors), proprioceptors (somatic receptors) and visual receptors by the brain. The vestibular apparatus (and cochlea) present in the ear contains mechanoreceptors that respond to the sense of hearing and equilibrium.

2. fluid-filled semicircular canals

Each ear has three semicircular canals, filled with endolymph, placed at right angles to each other. They are posterior, superior and lateral semicircular canals. The enlarged end of the semicircular canal is called as ampulla. The ampulla communicates with the axons of vestibular nerve.

Semicircular canals are involved in the maintenance of dynamic equilibrium, they sense the angular momentum. When we change the position of head, the endolymph lags behind, and pushes the cupula forward, in the opposite direction of the angular movement. This result in the activation of hair cells, depolarisation of these cells sends signals to the vestibular division of the vestibulocochlear nerve (eighth cranial nerve).

3. otolith organs

“Vestibule” lies between cochlea and semicircular canals. It contains utricle and saccule which are parts of membranous labyrinth. Maculae in the vestibule contains sensory receptors called, hair cells, which are essential to the mechanism of static equilibrium. The hair cells of maculae are embedded in the “otolithic membrane,” which contains small grains of calcium carbonate, called otoliths.

The maculae provide the information regarding the ups and downs of a path and to linear changes in speed, as it responds to the gravitational pull by means of otoliths. According to the gravitational pull, the otoliths cause the hair cells to depolarise or hyperpolarise, and then these hair cells send action potentials to the vestibular part of the eighth cranial nerve (vestibulocochlear nerve).

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