Equilibrium video Flashcards
What is Equilibrium?
- Awareness and monitoring of head position
- Monitored by utricle, saccule, semicircular ducts
- Information sent to brain to help keep our balance
What are the types of equilibrium?
Static equilibrium
* when body is steady
* monitored by utricle and saccule
Linear acceleration
* e.g., tilting your head to look at shoes
* also detected by utricle and saccule
Angular acceleration
* rotational movements of the head
* e.g., skater spinning on ice
* monitored by semicircular ducts
What is Maculae?
- Sensory receptors for static equilibrium
- One in each saccule wall and one in each utricle wall
- Monitor the position of the head in space, necessary for control of posture
- Respond to linear acceleration forces, but not rotation
- Contain supporting cells and hair cells
- Stereocilia and kinocilia are embedded in the otolithic membrane studded with otoliths (tiny CaCOz stones)
What type of movement does the macula detect, and how does it detect it?
The macula detects linear acceleration of the head. The position of the head influences the position of the otolithic membrane, distorting the stereocilia, causing changes in depolarization and neurotransmitter release.
Semicircular ducts relation to rotational movements
- Semicircular canal
- semicircular duct connected to the utricle
- Ampulla
- expanded region within each semicircular duct
- located at end farthest from utricle connection
What are Crista ampullaris?
Crista ampullaris
* elevated region on ampulla
* covered by epithelium of hair cells and supporting cells
What is Cupula?
Cupula
* overlying gelatinous dome
* kinocilia and stereocilia embedded here
* extends across semicircular duct to roof over ampulla
What is Detection of rotational movement ?
- with head rotation, lagging of endolymph
- pushes against cupula, causing bending of stereocilia
- results in altered neurotransmitter release from hair cells
- stimulation of sensory neurons
- bending of stereocilium in direction of kinocilium- leads to increased frequency of nerve signals
- response primarily to changes in velocity
Describe Vestibular sensation pathways
- Sensory neurons housed within vestibular ganglia
- monitor changes in activities of hair cells
- Equilibrium stimuli transmitted
- via vestibular branch of CN VIII
- Axons projecting to vestibular nuclei in medulla and cerebellum
- both integrate stimuli related to balance and equilibrium
- transmit signals through descending vestibulospinal tracts
- helps maintain muscle tone and balance
What type of movement do the ampullae detect, and how do they detect this movement?
The ampulla of the semicircular ducts detect rotational movements of the head. Endolymph pushes against the cupula, causing bending of the stereocilia and altering neurotransmitter release from the sensory neurons.
