1. Any object moving through space (such as an animal’s head) has six degrees of
ID: 50068 • Letter: 1
Question
1. Any object moving through space (such as an animal’s head) has six degrees of freedom. Three of these are translational. This means that motion can occur along the x-, y-, or z-axis. Simply put, this means moving forwards or backwards, moving sideways, ore moving up and down. The remaining three degrees of freedom are rotational, i.e. roll, pitch, and yaw. The primary sensory input for motion of the head is enabled by the
left and right retina in combination with cranial nerve pair II
left and right vestibular apparatus in combination with cranial nerve pair VIII
2. Translational motion is detected by the neuroepithelia of the
otolith organs
ampullae within the semicircular canals
3. Rotational motion is detected by the neuroepithelia of the
otolith organs
ampullae within the semicircular canals
4. Recall that the vestibulo-ocular reflex enables the eyes to remain fixed on target and that extrinsic eye muscles are innervated by brainstem -motor neurons. What role does the medial longitudinal fasciculus play in the vestibulo-ocular reflex?
central integration
links the vestibular nuclei with brainstem motor nuclei
5. Descending projections from the vestibular nuclei enable postural adjustments of the head and body. Any stereotypical change in head position that promotes balance is mediated by the vestibulo-cervical reflex. This name stems from the fact that most of the -motor neurons that control the position of the head are located in the motor nuclei of the
brainstem
cervical cord
6. Any stereotypical change in body position that promotes balance is mediated by the vestibulo-spinal reflex. Does this reflex implement the -loop?
yes
no
Explanation / Answer
1. Left and right vestibular apparatus in combination with cranial nerve pair VIII.
Vestibulocochlear nerve (Sensory, VIIIth cranial nerve), is the nerve of hearing and equilibrium. Ear is the organ of hearing and equilibrium, and the inner ear is supplied with the vestibule cochlear nerve. 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.
The semicircular canals 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) and thus transmits the equilibrium signals.
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