Audition Part 2 Flashcards
What two labyrinths make up the vestibular system? What are those labyrinths made up of?
The bony (vestibule and semicircular canals) and membranous labyrinths (semicircular ducts, saccule and utricle)
Where is the vestibular system?
In the petrous portion of the temporal bone
What secretes endolymph and where does it drain?
Secreted by cochlear duct, drained into dural sinuses via the endolymphatic duct
What secretes perilymph and where is perilymph drained?
Perilymph is secreted by the periosteum, and drained into CSF via the perilymphatic duct
What is Meniers disease? What are the symptoms and what is it caused by?
Excess production of endolymph creates pressure and causes malfunctioning signal transduction. Sympts include dizziness, vertigo, nausea, abnormal saccadic eye movements
What are the three semicircular ducts/canals?
Anterior (superior), horizontal (lateral) and posterior
What is the crista ampullaris? What is it made of?
It is the receptor in the ampulla of each semicircular canal. It contains a gelatinous mass called the cupula as well as receptor hair cells embedded within the cupula
What two types of hair cell projections are in the cupula?
Stereocilia and one kinocilium per hair cell
How does endolymph relay information about relative head motion?
As the skull turns, endolymph gains inertia within the semicircular canals, putting pressure on hair cells which relay signals about head motion
What is the macula? Where is it? What is it made of?
Receptor system in the saccule and utricle. Contains epithelial supporting cells with receptor hair cells. Supporting cells produce the otoliths gelatinous layer. On top of the gelatinous layer is the otoliths, calcium carbonate stones
In what planes of space are the macular of the saccule and utricle oriented?
The saccule is oriented in a vertical plane, the utricle is oriented in a horizontal plane
When the Stereocilia are deflected towards the kinocilium, is the firing rate of the sensory neuron increased or decreased?
Increased
Hair cell cilia are distorted by what two things?
Gravitational pull of the otoliths and inertia of the otoliths during movement
Sensory vestibular neurons join which cranial nerve?
The vestibulocochlear nerve, CN VIII
What are two common causes of vertigo?
Acoustic neuroma and Ménière’s disease
What is acoustic neuroma?
Benign tumor pressing against the vestibulocochlear nerve and facial nerve. Symptoms: nausea, vomiting, ipsilateral deafness, tinnitus
How is it that pressure on the vestibulocochlear nerve or vertigo can lead to nausea and vomiting?
Vestibular nuclei project to the solitary nucleus, a site of stomach afference
What is benign paroxysmal positional vertigo?
Dizziness, vertigo, nausea imbalance due to dislodged otoliths from trauma, infection or degeneration with age
Where do vestibular nuclei project to for postural control?
Thalamus and cortex
Where do vestibular nuclei project to for eye movements?
Brain stem nuclei
Where do vestibular nuclei project to for vascular control?
Autonomic centers
Vestibular nuclei communicate with what lobe for reflex and precision?
The flocculonodular lobe of the cerebellum
What is the vestibulo-ocular reflex for?
Tracking objects- movement of the head results in opposite movement of the eye
What is the neural pathway of the vestibulo-ocular reflex?
Head moves left, causes movement in the horizontal semicircular canals. Vestibular nerve –> reticular formation –> Abducens and oculomotor nerve –> eyes move right.
What does the VOR require for precision?
Vestibulo-cerebellar communication
What is physiological nystagmus?
Normal part of the VOR system, rapid movement of the eye after tracking to keep up with the head
What is pathological nystagmus?
Spontaneous rapid eye movements independent of head movement due to damage to one or more parts of the vestibular system
What is the neural pathway for the vestibulo-sympathetic reflex?
Vestibular nuclei –>RVLM –> IML cell column of the spinal cord
What does the vestibulo-sympathetic reflex do?
Enhances vasoconstriction during stress, postural syncope. Increased MAP, increased sympathetic control of skeletal muscle, kidney, blood vessels, but NOT GI. Increased skin vasoconstriction and sweating during nausea (eg. Sea sickness)
How does information get from the vestibular nuclei to the vestibular cortex? What are 5 areas of cortex that are involved here?
Vestibular nuclei –> thalamus (VPL) –> cortex such as the temporal parietal junction (TPL), and parietal areas 3aV, 2V, 7 and the insula
What is autoscopy? What is it caused by?
A condition in which one sees their own body in extrapersonal space, caused by incongruences among sensory inputs
What are three types of autoscopy?
Autoscopic hallucination, heautoscopy, and out-of-body experience
An out of body autoscopy is mainly due to a dysfunction in:
Strong vestibular dysfunction in the TPJ
Autoscopic hallucination is usually a result in what dysfunction?
Minimal vestibular dysfunction
Heautoscopy is usually due to what kind of dysfunction?
A mixture of strong vestibular dysfunction in the TPJ and minimal vestibular dysfunction
How does the vestibular system regulate cerebral blood flow?
Increasing MAP via baroreceptors and vasoconstriction. Also increases cerebral blood flow by vasodilation cerebral vessels.
The vestibular system dilates cerebral blood vessels via what two pathways?
Sympathetic inhibition: vestibular nuclei –> cerebellum–> RVLM –> inhibits constriction of cerebral vessels.
AND:
Vestibular nuclei –> solitary nucleus –> pteryyopalatine parasympathetic ganglion –> vasodilation of vessels
