physiology of ear Flashcards
what is sound
a pressure wave caused by oscillating molecules
-set in motion by a vibration
how is the inner ear designed as a receiver of sound
- curved spiral lamina
- coiled tubes of liquid
- scala media suspended in between scala tympani and scala vestibuli
what do the two opening of the cochlea to the middle ear do
permit transmission of pressure wave in enclosed canal and vibration of the basilar membrane
what opens the eustachian tube
tensor veli palatini and levator palatine muscles
how do the parts of the ear contribute to sound stimulation
external ear - sound collector
middle ear - mechanical force amplifier
inner ear - sound transducer/analyser
how does sound work
- wave passes through the chochlea maximally stimulating a particular area of the basilar membrane
- the organ of corti here depolarises and fires - stimulating the CN VII and then central pathways
- culminating activity in superior temporal gyrus
how old does a foetus have to be to hear
18 weeks
26 weeks to respond to sound
two types of hair cells in ear
kinocilium and stereocilia
how do the utricle and saccule help balance
- maculae of these organs have stereocilia projecting upwards into a gelatinous matrix with otoconia
- lend weight and due to gravity - brain perceives position and movement when tilting head or linear motion
what is the vestibulo-ocular reflex
gaze stabilizing reflex: the sensory signals encoding head movements are transformed into motor commands that generate compensatory eye movements in the opposite direction of the head movement, thus ensuring stable vision
what is nystagmus
Nystagmus is an involuntary rhythmic side-to-side, up and down or circular motion of the eyes that occurs with a variety of conditions
what are the outputs of the vestibular nuclei
- vestibulospinal tract - motor output to the neck, back and leg muscles (posture)
- medial longitudinal fasciculus and ocular muscles - motor output to eyes (gaze stabilisation)
- medial lemniscus and thalamus to cerebrum (awareness)
