29 Questions
What is the primary function of the cristae ampullaris in the vestibular system?
To detect changes in the position of the head
What is the role of the maculae in the vestibular system?
To detect sustained positions of the head
What innervates the maculae and cristae ampullaris?
CN VIII (vestibular nerve)
What is the effect of gravity on the vestibular hair cells?
It causes the hair cells to bend away from the utricle
What is the sequence of the 3 ossicles in the middle ear that transmit vibrations from the tympanic membrane to the inner ear?
Malleus → Incus → Stapes
Which of the following is NOT a central connection of the vestibular system?
Optic nerve
What is the membrane that separates the perilymph and endolymph in the cochlear duct?
Vestibular membrane
What is the structure responsible for converting mechanical sound stimuli into nerve impulses in the auditory system?
Organ of Corti
What is the pathway through which the remaining pressure waves in the scala tympani are dissipated?
Round window to the middle ear
What is the nerve that conveys the nerve impulses from the cochlea to the auditory cortex?
Cochlear nerve
What is the region of the brain where the auditory pathways terminate and sound is perceived?
Temporal lobe
What is the primary function of the vestibulo-ocular pathway?
To prevent slipping of the image from the fovea centralis during head movements
How do the corresponding ducts on opposite sides of the head function?
In pairs, with the same effects
What happens when the duct/canal of one side is stimulated?
The duct/canal of the opposite side is inhibited
What is the relationship between the horizontal ducts of opposite sides of the head?
They work together in the same plane
What is the result of the activity generated by the semicircular canals?
Compensatory eye movements in the direction opposite to head motion
Which extraocular muscles are stimulated by each semicircular canal?
A yoked pair of muscles that move the eyes in the same plane
What direction do the eyes move when the right horizontal canal is stimulated?
Towards the left
Which muscles are responsible for moving the eyes upward and to the left when the right anterior canal is stimulated?
Left superior rectus and right inferior oblique
What is the direction of eye movement when the right posterior canal is stimulated?
Downwards and to the left
Which nuclei are primarily responsible for controlling horizontal and vertical eye movements?
Medial and superior vestibular nuclei
What is the primary function of the vestibulo-ocular reflex?
To maintain gaze stability
Which direction is the head rotated when the right posterior canal is stimulated?
Backward and to the right
Which visceral motor functions are regulated by the vestibuloreticular pathway?
Vomiting, coughing, and cardiovascular functions
What is the primary function of the vestibuloreticular pathway?
Regulation of visceral motor functions
Which of the following is an example of the vestibuloreticular pathway in action?
A person experiencing dizziness and nausea while traveling by sea
What is the purpose of the doll's eye test?
To assess vestibular function in patients
How is the doll's eye test performed on an unconscious patient?
By holding the eyelids with thumb and index finger
What is the normal response to the doll's eye test?
Eyes move opposite to the head
Study Notes
Vestibular System
- Consists of receptors, vestibular nerve, and central connections
- Receptors: cristae ampullaris and maculae
- Innervated by CN VIII (vestibular nerve)
- Classified into dynamic receptors and static receptors
- Stimulus: position or changes in the position of the head
Auditory System
- Pathway of sound: sound waves enter the external ear, causing the tympanic membrane to vibrate
- Vibrations transmitted to the inner ear through the oval window via the 3 ossicles: malleus, incus, and stapes
- Pressure waves generated in the perilymph travel across the vestibular membrane to the endolymph of the scala media
- Basilar membrane ripples, causing the bending or displacement of hair cells in the Organ of Corti
- Mechanical sound stimulus converted into a nerve impulse
- Nerve impulses conveyed along the cochlear nerve, terminating in the auditory area of the temporal lobe of the central cortex
Vestibulo-Ocular Pathway
- Formed by the connection of the vestibular nuclei to the extraocular motor nuclei in the brainstem
- Main function: prevent slipping of the image from the fovea centralis during head movements
- Corresponding ducts on opposite sides of the head that lie in the same plane function in pairs
- Stimulation of one duct inhibits the duct on the opposite side
- Each semicircular canal stimulates a yoked pair of extraocular muscles that move the eyes in the same plane as the canal
Vestibulo-Reticular Pathway
- Projection of the vestibular nerve to the reticular formation through its connection to the reticular activating system
- Fibers come from the lateral and inferior vestibular ganglia and terminate on the reticular activating system and various visceral motor nuclei
- Projections are mainly ipsilateral
- Regulates visceral motor functions such as vomiting, coughing, cardiovascular functions, respiration, and speech function
Doll's Eye Test
- Aka Oculocephalic test
- Procedure used to elicit the vestibulo-ocular reflex
- Can be done to conscious and unconscious patients
- Examiner holds the eyelids with thumb and index finger and rotates the head from side to side while assessing eye movement
- Normal response: eyes move opposite to the head
Test your knowledge on the pathway of sound in the auditory system, from the external ear to the inner ear, including the transmission of vibrations through the ossicles and the journey of pressure waves through the cochlear duct. Learn about the different components involved in this process. Evaluate your understanding of the auditory system and its functions.
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