Physiology Flashcards
what does frequency of sound dictate?
pitch (high or low)
what does amplitude of sound dictate
intensity (quiet or loud)
what is 0 on an audiogram?
this is the hearing of a healthy 20-year-old male
what is considered normal hearing on an audiogram
hearing below 20-25
two ways the middle ear changes vibrations in the air to fluid vibrations in the cochlear
- tympanic membrane to oval window is 18:1
2. malleus handle is much bigger than the incus long process
what does the scala media contain?
endolymph
what is suspended between scala tympani and scala vestibuli?
scala media
what does the scala tympani and scala vestibuli contain?
perilymph
what does the frequency of sound vibrate in the cochlea?
different parts of the basilar membrane that hold hair cells (tonotopic organisation of the cochlea)
describe tonotopic organisation of the cochlea
high frequencies at the base
low frequencies at the apex
difference between inner and outer hair cells
inner hair cells sense sound
outer hair cells have a modulating effect (switch cochlea on and off)
pathway of the AP from hair cells to the brainstem
ECOLI eighth cranial nerve cochlear nucleus superior olivary complex lateral lemniscus inferior colliculus
where is sound perceived in the brain?
primary auditory cortex in left posterior superior temporal gyrus (Brodman areas 41/42) found in the temporal lobe
what opens the eustachian tube?
tensor veli palatini
levator palatine
what does dysfunction of opening the eustachian tube lead to?
negative middle ear pressure
what week in-utero can the foetus hear?
18 weeks
how many weeks when the foetus will respond to sound/voice
26 weeks
hearing is fundamental for speech development (milestones)
3 months recognises mothers voice
6 months turns to sound
input systems into balance
visual
cardiovascular (perfuses the systems involved with balance)
proprioceptive
vestibular
output systems of balance
vestibulopsinal tract
vestibulo-ocular reflex
vestibular end organs
SVN: lateral and anterior SCC and utricle
IVN: posterior semi-circular canal and saccule
two types of hair cells
kinocilium
stereocilia
what are the otolith organs
utricle
saccule
what do the utricle and saccule contain?
macules containing stereocilia projecting upwards into a gelatinous matrix with otoconia
describe the vestibular-ocular reflex
brain perceives position and movement when tilting head/linear motion
what are the receptors for taste and smell?
chemoreceptors
what do taste buds consist of?
sensory receptor cells and support cells arranged like orange segments
what are taste cell receptors replaced by?
basal cells
four types of papillae in the human tongue
filiform= most numerous but do not contain taste buds
fungiform, vallate and foliate all contain taste buds
describe the pathway of taste
- binding of chemicals to receptor cell alters ionic channels producing a depolarising AP
- afferent nerve fibres synapse with receptor cells
- signals are sent to cortical gustatory areas
ways afferent taste fibres reach the brainstem
CNVII= chorda tympani CNIX= supplies posterior 1/3rd of tongue CNX= epiglottitis and pharynx
five primary tastes
- bitter= stimulated by alkaloids, poison
- sour= acids containing free H+
- salt= NaCl
- sweet= stimulated by glucose
- umami (meat or savoury) triggered by amino acids
abnormalities of taste
ageusia
hypogeusia
dysgeusia
where is the olfactory mucosa located?
dorsal roof of the nasal cavity
what does the olfactory mucosa contain?
olfactory receptor cells
supporting cells
basal cells (secrete mucus)
describe the structure of olfactory receptor cells
neurone with a thick dendrite and expanded end called an olfactory rod which cilia project from and cause odorants to bind
role of basal cells in the olfactory mucosa
act as precursors for new receptor cells
what do afferent fibres of the olfactory nerve pierce?
cribriform plate and enter olfactory bulbs on the interior surface of the brain
where does the AP go once in the bulb?
passes along olfactory tracts to reach the temporal lobe and olfactory areas
during quiet breathing do odorants reach the olfactory mucosa?
no as this is situated above normal air flow
what allows odorants to reach the olfactory mucosa?
sniffing enhances the currant upwards
what must an odorant contain to be smelled?
it must be volatile enough
sufficiently water soluble (dissolve in mucous coating olfactory mucosa)
abnormalities of smell
anosmia
hyposmia
dysosmia
