chapter 15- balance

Question 1

what part of the ear is involved in balance?

Answer 1

the inner ear

Question 2

what is the inner ear?

Answer 2

sensory organ needed for hearing & balance
in Petrous Portion of Temporal bone
Posterior to the Eye Orbit
Extremely complex; functions in hearing & equilibrium

Question 3

what are the regions of the inner ear?

Answer 3

Vestibule, Semicircular Canals (Balance), Cochlea (Hearing)

Question 4

bony labyrinth

Answer 4

within the bone, series of bony cavities within temporal bone
lined by endosteum and contains perilymph (fluid like CSF)

Question 5

what makes up the bony labyrinth?

Answer 5

cochlea, vestibule, 3 semicircular canals (anterior, posterior, lateral)

Question 6

membraneous labyrinth

Answer 6

suspended within the bony labyrinth
filled with endolymph (K+ rich ICF), surrounded by perilymph

Question 7

what makes up the membraneous labyrinth ?

Answer 7

cochlear duct (hearing), saccule and utricle (sacs in anterior and posterior vestibule) and semicircular canals

Question 8

what does fluid do?

Answer 8

conducts sound vibrations in hearing and respond to mechanical forces during body position changes and acceleration

Question 9

how many parts make up the structural and functional organs of balance?

Answer 9

2 parts

Question 10

what does a static labyrinth consist of

Answer 10

utricle and saccule of the vestibule

Question 11

what does static labyrinth focus on?

Answer 11

body position in relation to gravity pushing down on you

Question 12

what does the static labyrinth respond to?

Answer 12

liner acceleration and deceleration

Question 13

what is responsible for maintaining proper head position in response to change in linear motion?

Answer 13

static labyrinth

Question 14

what is dynamic labyrinth associated with ?

Answer 14

semicircular canals

Question 15

what is dynamic labyrinth involved in evaluating?

Answer 15

movements of the head

Question 16

what is responsible for maintaining proper head position in response to rotational movement (turning)

Answer 16

dynamic labyrinth (kinetic)

Question 17

what parts make up static equilibrium ?

Answer 17

utricle and saccule of the vestibule

Question 18

what type of cells are the walls of the utricle and saccule made up of?

Answer 18

simple cubical epithelium

Question 19

where are the maculae located?

Answer 19

where the equilibrium receptor regions are

Question 20

what do the maculae respond to?

Answer 20

the pull of gravity and changes in head position

Question 21

what type of cells are involved in static equilibrium

Answer 21

specialized epithelium 2-3 mm in diameter
supporting cels and hair cells
1 cilium and many microvilli

Question 22

what is embedded in the otolithic membrane?

Answer 22

hair cells

Question 23

what are otoliths?

Answer 23

crystal-like structures composed of protein and CaCO3
“rocks”

Question 24

what are hair cells?

Answer 24

no axons, directly synapse with CN VIII

Question 25

where is the saccular macula?

Answer 25

perpendicular to the skull base

Question 26

where is the utricular macula

Answer 26

parallel to skull base

Question 27

true or false in an upright position the otolithic membrane does not move?

Answer 27

true

Question 28

what causes the otolithic membrane to move when the position of the head changes?

Answer 28

gravity

Question 29

what determines the intensity of hair cell stimulation?

Answer 29

the pattern of head movement

Question 30

true or false most info is perceived and handled consciously

Answer 30

false

Question 31

how does the body respond to information about head position?

Answer 31

by making subtle tone adjustments in muscles of th back and neck to help return the head to a neutral position

Question 32

does dynamic equilibrium have otoliths?

Answer 32

no- no response to gravitational pull

Question 33

what is dynamic equilibrium associated with?

Answer 33

semicircular canals- allow movement detection in all directions

Question 34

what is the ampulla?

Answer 34

base with enlarged swelling where equilibrium receptor called the crest ampullaris is

Question 35

what is dynamic equilibrium structurally and functionally similar to?

Answer 35

sensory epithelium of maculae

Question 36

what does the crust ampullaris respond to?

Answer 36

rotational head movements

Question 37

what does dynamic equilibrium consist of ?

Answer 37

crest of epithelium with cupula (curved gelatinous mass)

Question 38

what is embedded in the cupula?

Answer 38

crista hair cells

Question 39

what is a cupula?

Answer 39

float displaced by fluid movements with semicircular canals helps evaluate movements of the head?

Question 40

how does the cupula move?

Answer 40

endolymph moves within the semicircular canals to move the cupula hairs bend and AP is generated

Question 41

when a person is still, what happens to the cupula?

Answer 41

it is stationary

Question 42

when a person bends forward, what happens?

Answer 42

semicircular canals begin to move with the body but the endolymph remains stationary. cupula moves in direction opposite of the direction of movement.

Question 43

what happens as movement continues?

Answer 43

endolymph in semicircular canals catches up with the cupula and stimulation stops.

Question 44

what happen when the head stops moving?

Answer 44

endolymph continues to move because of the momentum, it displaces the cupula in the same direction that the head was moving.

Question 45

when is displacement of the cupula most intense?

Answer 45

when the rate of the head movement changes

Question 46

is the info that the brain obtains from dynamic labyrinth conscious or subconscious?

Answer 46

subconscious

Question 47

where does the nervous system pathway for balance receive info from?

Answer 47

inner ear signals (vestibular apparatus) sensory input from proprioception receptors are throughout the body and visual system

Question 48

what is proprioception?

Answer 48

sense of self-movement, force, and body position

Question 49

what is proprioception mediated by?

Answer 49

proprioceptors - receptors/ mechanosensory neurons in muscles, tendons, and joints

Question 50

why are signals integrated?

Answer 50

allows body to maintain posture and balance

Question 51

where is the sensory input that you are consciously aware of detected?

Answer 51

through the cerebrum

Question 52

where are the APs associated with balance pathways conducted to ?

Answer 52

vestibular area of the cerebral cortex ONLY

Question 53

what happens to the # of hair cells in saccule, utricle, and ampullae, as well as the # of otoliths?

Answer 53

it decreases

Question 54

what is the effect of having less hair cells and otoliths as we age?

Answer 54

the elders are less sensitive to gravity, acceleration, and rotation, making them get dizzy and fall more easily

Question 55

where do the neurons synapsing on hair cells of maculae and cristae ampullares converge into?

Answer 55

the vestibular ganglion- where cell bodies are located

Question 56

where do sensory axons from the vestibular ganglion pass through?

Answer 56

the vestibular nerve to the vestibular nucleus within the brainstem

Question 57

What other places within the CNS do the vestibular nucleus' axons run ?

Answer 57

spinal cord, cerebellum, and cerebral cortex cerebellum influences postural muscles.

Question 58

where else do vestibular nuclei axons also synapse? what do they do?

Answer 58

within motor nuclei or CN III, IV, VI these control reflexive movements of the extrinsic eye muscles

Question 59

do the vestibular nuclei axons also go to posterior ventral nucleus of the thalamus?

Answer 59

yes

Question 60

what are thalamic neurons that project to vestibular areas of cerebral cortex responsible for ?

Answer 60

conscious awareness of balance