hearing, balance, taste and olfaction

Question 1

sound

Answer 1

sound is a longitudinal wave
frequency of sound is the number of cycles per second (Hz)
amplitude of sound waves=Db
as air pressure goes up and down it causes movement in the ear drum and that allows us to perceive sound

Question 2

3 parts of the ear

Answer 2

outer ear (pinna)
middle ear (ossicles)
inner ear (cochlea and labyrinth)

Question 3

role of the pinna

Answer 3

capture sound efficiently
sound localisation
ridges and bumps of outer ear reflect sound and focus it into the auditory canal

Question 4

what is the auditory canal filled with?

Answer 4

air

Question 5

where does the outer ear stop?

Answer 5

tympanic membrane (ear drum)

Question 6

role of the middle ear

Answer 6

transmit mechanical energy captured at the ear drum from sound through the ear to the cochlea

Question 7

role of the inner ear

Answer 7

mechanical energy - fluid waves - action potential

Question 8

what are the 3 bones of the ossicles?

Answer 8

malleus, incus and stapes

Question 9

how do the ossicles and ear drum enable the amplification of sound information?

Answer 9

ossicles are stiff and the ear drum is larger than the oval window where the stapes is means we have an increase in 25 in the energy going from the ear drum to the window

Question 10

direction of the ossicles

Answer 10

tymapnic membrane- malleus- incus- stapes terminates at the oval window

Question 11

what muscles are by the ossicles?

Answer 11

stapedius and tensor tympani muscles

Question 12

what is the role of the stapedius and tensor tympani?

Answer 12

secure the ossicles and the membrane
protect these structure when there is a loud sound by contracting

Question 13

what is the middle ear filled with?

Answer 13

air

Question 14

what is the cochlear composed of (scalae)?

Answer 14

scala vestibululi (starts in the oval window)
scala media
scala tympani (ends in round window)

Question 15

what is the cochlea filled with?

Answer 15

fluid

Question 16

what is the organ of corti?

Answer 16

runs the entire length of the cochlea and contains the hair (auditory) receptors along the basilar membrane

Question 17

pathway of sound

Answer 17

sound causes tympanic membrane to vibrate
these vibrations are passed via the ossicles to the oval window
this causes the stapes to vibrate against the oval window and this generates a fluid wave that travels down the length of the cochlea
oscillatory pressure differences propagate along the scala vestibuli and tympani

Question 18

what is the hole at the end of the basilar membrane called?

Answer 18

helicotrema

Question 19

what does the helicotrema allow?

Answer 19

fluid wave to pass through and come down the scala tympani

Question 20

what happens to left over energy in the ear?

Answer 20

round window bulges out and that absorbs remaining energy so fluid wave can continue

Question 21

what does a fluid wave do to the basilar membrane?

Answer 21

causes it to move so the hair cells start to move in response to the changing in fluid pressure

Question 22

what are the two ends of the basilar membrane?

Answer 22

basal (narrow by stapes) and apical (wide)

Question 23

hair cells on the basal end respond to…

Answer 23

higher frequencies because they are stiff

Question 24

hair cells on the apical end respons to…

Answer 24

lower frequencies because they are flexible

Question 25

what is tonotopy?

Answer 25

a map of sound created at the basilar membrane (low and high frequencies)

Question 26

what partially covers the organ of corti?

Answer 26

the tectorial membrane that causes hair cells to bend

Question 27

role of inner hair cells

Answer 27

fine perception of sound

Question 28

role of outer hair cells

Answer 28

fine tuning (more outer than inner)

Question 29

central auditory pathway

Answer 29

hair cells- cochlear ganglion cells (spiral)- dorsal and ventral cochlear nuclei in medulla- ventral to superior olivary nuleus to inferior colliculus/dorsal straight to IC- medial geniculate nucleus in thalamus- primary auditory cortex

Question 30

why is it functionally important that the ventral cochlear nuclei is contralateral and ipislateral?

Answer 30

bilateral representation of sound in an early stage of the pathway (means damage to auditory cortex wont necessarily mean being deaf in one ear)

Question 31

functions of the vestibular system

Answer 31

balance
visual stability
spatial orientation
autonomic functioning

Question 32

what 2 sets of structures in the vestibular labryrinth help us detect balance?

Answer 32

otolith organs and semicircular canals

Question 33

what structures does the otolith organs contain?

Answer 33

utricle and saccule

Question 34

what do otolith organs detect?

Answer 34

detect the force of gravity and head tilits

Question 35

what do the semicircular canals detect?

Answer 35

3 perpendicular canals that are sensitive to rotational accleration

Question 36

how do otolith organs cause depolarisation?

Answer 36

if hairs bend in direction of the largest hair then there will be an action potential
as head tilits forward, intertia carries gelatinous cap to move forward and hair bends in the direction of the kinocilium

Question 37

how do semicircular canals cause depolarisation?

Answer 37

when youre spinning, the endolymph in the canals moves and that causes the hair cells in the cupula to bend causing exictation of the dendrites of neurons in the vestibular ganglion

Question 38

principle vestibular pathway

Answer 38

hair cells- vestibular ganglion cells- vestibular nuclei via the vestibulocochlear nerve- ventral posterior nucleus- somatosensory cortex

Question 39

what nuclei does the vestibulocochlear nerve also innervate?

Answer 39

oculomotor
trochlear
abducens
(eye movement)
accessory

Question 40

how do we detect smell?

Answer 40

chemoreceptors
chemicals in air are breathed in and they become dissolved in the mucus lining the top of the nasal cavity

Question 41

where are the cilia of the olfactory cells located?

Answer 41

the mucus of the nasal cavity

Question 42

olfactory epithelium

Answer 42

axons of the olfactory receptor cells constitute the olfactory nerve and penetrate the cribriform plate of the skull

Question 43

what happens when smell information enters the brain?

Answer 43

olfactory synapses with mitral cells in glomeruli contained within the olfactory bulb (ventral surface)
second-order neurons then form the olfactory tract which pass along the bulb

Question 44

what is different in the ascedning sensory pathway of olfaction compared to the other special senses?

Answer 44

there is no synapse within the thalamus

Question 45

what lobe is the olfactory cortex/piriform in?

Answer 45

temporal lobe- conscious perception of smell

Question 46

what areas of the brain is the olfactory tract assoiated with?

Answer 46

olfactory cortex, hippocampus (olfactory memory), amygdala (emotional responses), reticular formation (visceral responses to smell) and the orbitofrontal cortex

Question 47

where are taste buds located?

Answer 47

papillae in the tongue and palate

Question 48

how do we taste?

Answer 48

each taste bud has 50-150 taste receptor cells arranged within the bud
microvilli at the apical end of the taste cells extend into the taste pore, the site where chemicals dissolved in saliva can interact with taste cells
this activates gustatory axons

Question 49

gustatory pathway

Answer 49

facial and glossopharyngeal nerve (and vagus)
information rises up and synapses in the nucleus of the solitary tract in the medulla oblongata
main ascedning taste information arrives at the ventral posterior medial nucleus of the thalamus
travels to the gustatory cortex in the insula (floor of lateral sulcus)

Question 50

collateral pathways for gustation

Answer 50

brain regions for control of: respiration, satiety & feeding, muscles of mastication and muscles of swallowing