Sound and Hearing Flashcards
what is sound?
- sound is produced when matter is acted upon
- vibration that propagates as an acoustic wave
- sound energy
- produced in many activities (Eg. voice)
what are the two properties of sound?
amplitude (loudness) and frequency (pitch)
what is the frequency?
- measured in hertz (cycles per second)
- pitch is the frequency of waves in a given amount of time - depends of frequency
- higher pitch - higher frequency
- lower pitch - lower frequency
what is amplitude?
- sound pressure level
-magnitude of sound - loudness
-measured in decibels - 70 dBA or lower is safe hw 85 dBA or higher can damage your hearing
why is hearing useful?
helps us converse with other people, learn by listening, hear music and shows and podcasts and alert us of dangers
what are the hearing structures for the outer ear?
pinna - funnel sound energy toward ear
external auditory meatus
tympatic membrane
what are the hearing structures for the middle ear?
ossicles - 3 bones in ear
ligaments and muscles
what are the hearing structures in the inner ear?
cochlea
auditory nerve
when do we do our best hearing?
because of the shape of the ear we do our best hearing face to face - funnel and capture info and magnifies the sound
external auditory meatus - description of the structure
- small opening surrounded by cartilage (makes up the pinna)
- medial two thirds are bony
- proximal end is closed at the T.M
role of the external auditory meatus
- conducts sound energy from concha to the T.M
- role is resonator- amplify certain pitches/ freq or sound b4 reaching the tympatic membrane
tympatic membrane - description of the outer ear structure
- 8-10mm diameter with 3 layers (0.0001m thick)
- “cone of light” via otoscope - see the bottom portion will shine
- used to be labelled the eardrum - now the TM
- boundary bw outer and middle ear
tympatic membrane - function of the outer ear structure
- function is that sound energy is funneled in
- hits membrane and causes it to vibrate from sound energy
ossicles - structure within the middle ear
- smallest bone in the human body
- extends from human body extending
from T.M to oval window of cochlea - 3 ossicles in ear- malleus (hammer), incus (anvil), stapes (stirrup)
ossicles - function within the middle ear
amplify the sound energy applied to the T.M to the fluid in the cochlea
pharyngotympanic or eustachian tube - structure within the middle ear
- Aka. The auditory tube
- 3.8 cm tube running from middle ear to nasopharynx
- cartilaginous and flexible toward the nasopharynx where it is usually closed
pharyngotympanic or eustachian tube - function within the middle ear
- opens occasionally to equalise the pressure in middle ear
- also functions to drainage mucus
what part of the ear is the semicircular canal?
inner ear
semicircular canal role within inner ear
essential for balance
bony labrynth - within the inner ear
- oval window - footbed of the stapes (ossicles), movement on oval window will move fluid called perilymph
- round window - perilymph exerts force on round window, causing it to slightly bulge
cochlea - structure
- coil like structure - comes up and down
- filled with perilymph
- scala vestibuli - spiral up
- scala tympani - spiral down
cochlea - function / description
- movement of perilymph leads to movement of the basilar membrane
- movement the basilar membrane means hair cells bend which causes action potential to be sent along the cochlea nerve
cranial nerve 8 - CNVIII
- auditory nerve - part of cranial nerve VIII
- afferent fibres will carry signal to central nervous system structures that
allow us to:
- converse w other ppl, learn by listening, hear music/podcast - temporal lobe
- moves head toward sound ( brainstem)
order of the hearing process
external sound energy, funnelled by the pinna, external auditory meatus, tympanic membrane, amplified through the ossicles, oval window, move perilymph, move hair cells, action potential, CNVIII, Primary auditory cortex
auditory perception
- ability to receive, identify and attach meaning to sounds
- perception is the ability to interpret info that our senses receive from the environment
- interpretation is an active process that depends on our cognitive processes and prior knowledge
- relies on the auditory cortex and association nerves
- eg. recognise someone via listening to their voice, sirens
types of hearing impairments
- conduction deafness
- sensorineural deafness
- tinnitus
- menieres syndrome
what is conduction deafness?
- hampers sound conduction to the fluids of the inner ear
- eg. impacted ear wax, perforated eardrum, osteosclerosis of the ossicles,
sensorineural deafness
damage to the neural structures at any point from the cochlear hair cells to the auditory cortical cells
tinnitus
- ringing or clicking sound in the ears in the absence of auditory stimuli
- disorder of the cochlea
menieres syndrome
- entire labrynth disorder
- affects cochlea and semicircular canals
- causes vertigo, nausea, vomiting
structural types of neurons
unipolar
bipolar
multipolar
unipolar
- one process of the cell body: mainly sensory neurons
- neuron that is unipolar has an axon that extends into dendrites
bipolar
- cell body positioned in the middle of the neuron - has both an axon and a dendrite extending from the stoma
- two processes of the cell body mainly special sensory neurons
multipolar
- two or more dendrites and one axon
- many processes of the cell body: mainly motor
functional types of neurons
sensory, motor and interneuron
sensory neurons
carry sensory info from receptors to CNS eg. touch of skin, taste
motor neurons
carry action potential from CNS to the PNS to effect the muscles
interneurons
in CNS only to facilitate efficient communication bw neurons
What is the structural difference bw a neuron classified as myelinated compared to unmyelinated?
- myelinated axon have Schwann cells tightly coiled around them
axons have larger loose Schwann cells in unmyelinated neurons around a group of axons
What is the functional difference bw a neuron classified as myelinated compared to unmyelinated?
speed of transmission of nerve impulses is high in myelinated nerve fibres. hw unmyelinated nerve fibres don’t have myelin insulations, tf the speed of transmission of nerve impulses is slow
Describe similarities and differences bw spinal nerves and cranial nerve
- similar - both nerves, part of the PNS, can be motor/sensory OR both
-differences - spinal nerves connect body structures (eg. bicep) to the CNS whereas Cranial nerves connect the head and neck structures to Brain and Brain Stem
Where are the spinal and cranial nerves in the body?
- spinal nerve - in the spinal cord
-cranial nerve - in the head
Explain the difference between nerve fascicles and peripheral nerves
- peripheral nerves are formed by bundles of fascicles grouped by epineurium
- nerve fascicles are surrounded by another layer of connective tissue - perineurium
