equilibrium

Question 1

Vestibular apparatus

Answer 1

• equilibrium receptors in semicircular canals and vestibule
• vestibular receptors monitor static equilibrium –> linear acceleration/deceleration and head movements
• semicircular canal receptors monitor dynamic equilibrium –> rotational movements and acceleration/deceleration

Question 2

Maculae

Answer 2

• one in each saccule wall (vertical orientation) and one in each utricle wall (horizontal orientation)
• monitor position of head in space (necessary for posture control)
• respond to linear acceleration forces (not rotational)
• contain supporting cells and hair cells
• stereocilia and kinocilia are embedded in the jelly-like otolithic membrane studded with otoliths (tiny CaCO3 stones)

Question 3

Activating maculae receptors

Answer 3

• hair cells release NT continuously
• movement modifies the amt released
• bending of hairs in direction of kinocilia depolarizes hair cells –> increases amt of NT released –> more impulses travel up vestibular nerve to brain
• bending hairs away from kinocilium hyperpolarizes receptors –> less NTs released –> reduces rate of impulse generation

Question 4

Crista Ampullares (Crista)

Answer 4

• sensory receptor for rotational acceleration
• one in ampulla of each semicircular canal
• each crista has supporting cells and hair cells that extend into gel-like mass called ampula cupula
• dendrites of vestibular nerve fibers encircle base of hair cells

Question 5

Activating Crista Ampullaris receptors

Answer 5

• cristae respond to changes in velocity of rotational movements of the head
• bending of hairs in cristae causes depolarizations and rapid impulses reach brain at faster rate
• bending of hairs in opposite direction causes hyperpolarization and fewer impulses reach brain

Question 6

What happens when you spin?

Answer 6

• THere’s a lag in the endolymph
• fluid flows in opposite direction, bending hair, and opening K chnnels

-once motion stops, endolymph flows in opposite direction

Question 7

Equilibrium Pathway to brain

Answer 7

• equilibrium info goes to reflex centers in brain stem
• allows fast, reflexive response to imbalance
• impulses travel to vestibular nuclei in brain stem or cerebellum, both of which revieve other inputs
• 3 modes of input for balance and orientation
• vestibular receptors
• visual receptors
• somatic receptors

Question 8

Motion Sicknes

Answer 8

• sensory input mismatches
• visual input differs from equilibrium input
• warnings: exess salivation, pallor, rapid deep breathing, profuse sweating
• treatment with antimotion drugs that depress vestibular input such as meclizine and scopolamine