8.4 Equilibrium and orientation Flashcards
What are the two main parts for maintaining quilibrium and orientation
Vestibular apparatus: equilibrium receptors maintains our orientation and balance
- > vestibular receptors: monitors static equilibrium or linear acceleration
- > semicircular canal receptors: monitors dynamic equilibriium or angular acceleration
what is the vestibule
- suspended in its perilymph are two sacs: saccule and utricle
- these sacs house equilibrium receptors called maculae that respond to gravity (linear acceleration) and changes in the position of the head
describe the maculae
- sensory receptors for static equilibrium and linear acceleration
- each hair cell has stereocilia and kinocilium embedded in the otolithic membrane
Describe the Otolithic membrane
- jellylike mass studded with tiny CaCO3 stones called otoliths (dense structures that interact with hair cells)
what are the hair cells that respons to movement in the maculae
Utricular hairs respond to horizontal movement (running)
Saccular hairs respond to vertical movement (jumping)
describe utricular receptor cells
Otolithic movement in the direction of the kinocilia causesdepolarizes vestibular nerve fibers
Movement in the opposite direction causes hyperpolarizes vestibular nerve fibers
describe saccular receptor cells
At rest: about 10% of ion channels are open, and topic signal sent by sensory enuron
excitation: hair cell bends in one direction causing cell to depolarize -> inc action potential frequency in associated sensory neuron
inhibition: if hair cells bend in opp direction, ion channels close, hyperpolarization and sensory neuron signals decrease
describe semicircular canals
- respond to angular acceleration (rotation)
- lie in the 3 spaces of space and ocmmunicate with the utricle
- ampulla is swollen end of each canal and houses equilibrium receptors in a region called crista ampullaris
- receptors respond to angular movements of head
role of crista ampullaris in dynamic equilibrium
- senses iff types of movement
- Posterior: head tilt left and right
Anterior canal/superior canal: nod yes
Lateral canal/horizontal canal: head shake no
Describe rotary head movement
- head head turns right, endolymph shes the cupula to left
*fluid and cupula move in the same direction
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how is vestibular input processed
- vestibular apparatus -> vestibular branch of nestibulocochlear nerve -> cerebellum (imp balance)
- vestibular apparatus -> vestibular branch of nestibulocochlear nerve -> vestibular nuclei of medualla -> reticular formation -> thalamus -> cerebral cortex
how is balance and oreintation maintained?
Vestibular receptors
Visual receptors
Somatic receptors
- these receptors allow our body to respond reflexively