Auditory pathway to brain LO4

Question 1

Balance or Equilibrium

Answer 1

• is the response felt by head movements (frequently without awareness)
• the role of equilibrium is to provide information about the location of our
  head, the movement of our head, how rapid and in which direction the
  movement
• equilibrium depends on inputs from the internal ear, as well as, vision and information from proprioceptors of muscles and tendons

Question 2

Static equilibrium:

Answer 2

evaluating the position of the head relative to gravity
(up/down) and forward/backward. Information supplied when the head is motionless, or moving in a straight line – detected by hair cells in the
vestibule (saccule and utricle)

Question 3

Dynamic equilibrium

Answer 3

evaluates the position of the head while it is rotating, or moving in an angular direction – detected by hair cells in the semicircular canals

Question 4

Vestibule - equilibrium

Answer 4

contains 2 membranous sacs
– saccule: continuous with
cochlear duct
– utricle: continuous with
semicircular canals
* both contain equilibrium receptors
* utricle & saccule contain hair cells that are embedded in jellylike substance
* tiny ear stones (otoliths) are embedded in the surface of the jelly

Question 5

Static Equilibrium

Answer 5

When head position is
changed, gravity pulls on
the stones and distorts
the jelly, bending the
equilibrium hair cells in
vestibule
* distortion of the hair cells
is the stimulates depolarisation

Question 6

Semicircular Canals

Answer 6

• 3 fluid filled canals that lie in three planes of space
• equilibrium hair cells respond to rotational movement of the head

Question 7

Dynamic Equilibrium:
Semicircular Canals

Answer 7

• contain hair cells surrounded by endolymph
• angular movement moves endolymph
• endolymph movement bends and distorts
  hair cells

Question 8

Equilibrium pathway

Answer 8

*distortion of the hair cells (vestibule and semicircular
canals) stimulates depolarisation of vestibular division of the
vestibulocochlear nerve
* action potentials travel to:
* the reflex centres (vestibular nuclei) of the brainstem
* cerebellum
* vestibular cortex of the insula