8.4 Equilibrium and orientation

Question 1

What are the two main parts for maintaining quilibrium and orientation

Answer 1

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

Question 2

what is the vestibule

Answer 2

• 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

Question 3

describe the maculae

Answer 3

• sensory receptors for static equilibrium and linear acceleration
• each hair cell has stereocilia and kinocilium embedded in the otolithic membrane

Question 4

Describe the Otolithic membrane

Answer 4

• jellylike mass studded with tiny CaCO3 stones called otoliths (dense structures that interact with hair cells)

Question 5

what are the hair cells that respons to movement in the maculae

Answer 5

Utricular hairs respond to horizontal movement (running)

Saccular hairs respond to vertical movement (jumping)

Question 6

describe utricular receptor cells

Answer 6

Otolithic movement in the direction of the kinocilia causesdepolarizes vestibular nerve fibers

Movement in the opposite direction causes hyperpolarizes vestibular nerve fibers

Question 7

describe saccular receptor cells

Answer 7

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

Question 8

describe semicircular canals

Answer 8

• 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

Question 9

role of crista ampullaris in dynamic equilibrium

Answer 9

• senses iff types of movement
• Posterior: head tilt left and right

Anterior canal/superior canal: nod yes

Lateral canal/horizontal canal: head shake no

Question 10

Describe rotary head movement

Answer 10

• head head turns right, endolymph shes the cupula to left

*fluid and cupula move in the same direction

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Question 11

how is vestibular input processed

Answer 11

• 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

Question 12

how is balance and oreintation maintained?

Answer 12

Vestibular receptors

Visual receptors

Somatic receptors

• these receptors allow our body to respond reflexively