martin chapter 12 Flashcards
what do vestibular receptors sense?
head motion, both linear (such as the one experienced during fast acceleration in a jet) and angular (such as during turning)
vestibular receptors are located in 5 peripheral vestibular organs
the three semicircular canals (which signal angular acceleration) and the utricle and the saccule (which signal linear acceleration)
vestibular receptors are hair cells innervated by?
bipolar neurons whose cell bodies are in the vestibular ganglion
the axons of these bipolar neurons travel to the brain stem through? and terminate where?
the vestibular division of cranial nerve VIII and terminate in the vestibular nuclei
4 separate vestibular nuclei
inferior
superior
medial
lateral
the primary thalamic relay of vestibular nuclei is?
the ventral posterior nucleus
axons form the vestibular nuclei ascend bilaterally reaching several sites within and around the ventral posterior nucleus
3 major areas within the parietal lobe and insular cortex receive vestibular information
vestibular cortical areas:
1.the insular cortex and 2.posterior parietal lobe (area 2V) play a role in the conscious awareness of vestibular sensory activation and in sensing body orientation and the orientation of the world around us
3. area 3a at the base of the central sulcus (part of the primary somatic sensory cortex) participates in sensing head position in conjunction with proprioceptive afferents in neck muscles
3 key areas that receive vestibular input from the thalamus
insular cortex
area 2v
area 3a
how is vestibular regulation of blood pressure accomplished?
through connections with the brain stem visceral integrative centers (solitary, vagal and parabrachial nuclei) that, in turn, regulate autonomic nervous system function
for axial muscle control, the vestibular nuclei receive info primary from?
cerebellum and cerebral cortex
two distinct descending projections of vestibular nuclei for balance and coordinating head and eye movements
lateral and medial vestibulospinal tracts
these two form a major portion of the medial descending motor pathways
beginning of the lateral vestibulospinal tract
lateral vestibular nucleus
this pathway begins in this nucleus and descends ipsilaterally in the white matter to all spinal levels
this pathway is crucial for controlling posture and balance
beginning of the medial vestibulospinal tract
medial vestibular nucleus
this pathway begins in this nucleus and descends bilaterally in the white matter but only to the upper cervical spinal cord
this pathway plays a role in controlling head position in relation to eye position
each eye is controlled by 6 muscles that work as 3 functional pairs
lateral and medial rectus muscle move the eyes horizontally (abducting and adducting respectively)
superior and inferior rectus muscles elevate and depress the eye (especially when the eye is abducted)
superior and inferior oblique muscles depress and elevate the eye (especially when the eye is adducted9
the axons of the oculomotor nucleus contribute in forming what?
most of the oculomotor nerve (III)
the oculomotor nucleus innervates 4 out of 6 extra ocular muscles
- medial rectus
- inferior rectus
- superior rectus
- inferior oblique
this nucleus also innervates the elevator palpebrae superioris muscle (eyelid elevator)
how can we define the trochlear and abducens nuclei?
2 of the extra ocular motor nuclei
motor neurons in the trochlear nucleus give rise to?
to the fibers in the trochlear nerve (IV), which innervates the superior oblique muscle
which is the only cranial nerve that exits from the dorsal brain stem surface?
the trochlear nerve
NB: all of its axons decussate within the CNS
the axons of the motor neurons of the abducens nucleus form?
the abducens nerve (VI)
abducens motor neurons innervate the lateral rectus muscle
where do neurons in vestibular nuclei that partecipate in eye movement control project their axons?
into the medial longitudinal fasciculus to synapse on motor neurons in the oculomotor, trochlear and abducens nuclei.
