physiology-ear Flashcards
what dictates the pitch of a sound?
frequency
what dictates the intensity of a sound?
amplitude
what frequency can humans hear?
20Hz-20,000Hz
what graph can be used to cover hearing range?
audiogram
what do the ‘O’ and ‘X’ represent in an audiogram?
o= right ear air conduction
x=left ear air conduction
what allows amplification of sound in the middle ear?
-size of tympanic membrane compared to oval window (18:1)
what are the three parts inside the cochlear?
- scala tympani (contains perilymph)
- cochlear duct/ scala media (contains endolymph)
- scala vestibuli (contains perilymph)
where are the inner hair cells found in the cochlea?
-in the organ of corti
what is the role of the inner hair cells?
-involved in receiving sound and passing the sound up the auditory nerve by turning it into action potential (they sway causing voltage gates to open, causing depolarisation, creating an action potential)
what is the role of the outer cells?
-modifying sound
where is the primary auditory complex located?
left posterior superior tempoal gyrus (Broadmans area 41/42)
what is the role of the eustachian tube?
equalise pressure in ears
what is the resting state of the eustachian tube like?
-it is closed but can be opened by tensor veli palatini and levator palatine muscles
what role does have external ear have in hearing?
sound collector
what role does the middle ear have in hearing?
mechanical force of amplification
what role does the inner ear have in hearing?
sound transducer/analyser
at what age in the utero can a foetus hear?
18 weeks
at what age in the utero can a foetus respond to sound/voice?
26 weeks
what system in your ear is responsible for balance?
vestibular system
what nerve supplies the lateral, anterior semi-circular canal and utricle?
SVN (superior vestibular nerve)
what nerve supplies the posterior semicircular canal and saccule?
-inferior vestibular nerve (IVN)
what are the longest hair cell?
kinocilium
what are stereocilia?
hair cells that increase in length until the kinocilium (longest hair cell) (found in the semicircular canals)
what occurs if there if the stereocilia move towards compared to away from the kinocilium?
towards- increase in action potential
away- decrease in action potential
what allows you to percieves position and movement when tilting head or linear motion?
- in the utricle and saccule there is maculae
- maculae of these organs have stereocilia projecting upwards into a gelatinous matrix with otoconia (otolith organs)
- this means when you move head/tilt it the hair cells drag allowing you to feel motion
what occurs to firing rate of hair cells in semicircular ducts as you tilt head left/right horizontally?
left= inhibition so decrease in firing rate
right=excitation so increase in firing rate
what allows you to stabilize your gaze?
vestibular ocular reflex
what is nystagmus?
-a rhythmical, repetitive and involuntary movement of the eyes
what occurs if you have right vestibular damage?
you think youre turning left when you aren’t actually
-can cause vertigo
what is bi directional nystagmus?
look to left- eye moves fast to left
look to right- eye moves fast to right
-indicates a central vestibular problem
what does communications in vestibular nuclei with outputs to the vestibular tract involve?
- motor output to neck, back and leg muscles
- involves posture
what does communications in vestibular nuclei with outputs to the medial longitudinal fasciculus and ocular muscles involve?
motor output to eyes
-gaze stabilisation
what does communications in vestibular nuclei with outputs to the medial lemniscus and thalamus to cerebrum involve?
awareness
