Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Audiology and hearing health professionals in developed and developing countries wikipedia , lookup
Noise-induced hearing loss wikipedia , lookup
Olivocochlear system wikipedia , lookup
Sensorineural hearing loss wikipedia , lookup
Sound from ultrasound wikipedia , lookup
Evolution of mammalian auditory ossicles wikipedia , lookup
Senses 1 Introduction to physiology of senses Sense of hearing Sense of balance Practical tasks Otoscopy Tests with tuning forks Audiometry Examination of nystagmus http://t2.gstatic.com/images?q=tbn:ANd9GcQLxYEdEk8lRTuToHhhLhGTIA OfpOUYUkXwbLaC9dD3FYcpm2XA Senses • gather the stimuli occurring in our external or internal environment, transmit this information to the CNS, process it and allow for sensation an perception • crucial for survival: – provide necessary warning to avoid injury, e.g. feeling heat, seeing danger – external receptors – to maintain homeostasis – internal receptors – make it possible for the body to respond to stimuli • special senses – – – – – vision hearing taste smell balance • general (somatic) senses – touch – temperature – pain Each of the principal types of sensation that can be experienced pain, touch, sight, sound, taste, etc. is called a modality of sensation. Sensory receptors • specialized cells or free nerve endings • sensitive to various forms of energy (energy = stimulus) • stimulation elicits receptor potential (change in membrane potential – depolarization or hyperpolarizing) • receptors detect also the intensity of a stimulus • convert the stimulus to nerve impulses (action potential) Distribution of receptors - receptors of special senses – grouped in specific areas of the body or in complex organs - general sense receptors – distributed throughout the body – skin, mucosa, joints, muscles, tendons, viscera Classification of receptors • Mechanoreceptors – activated by mechanical stimuli -deformation, stretching, changing position of the receptor (e.g. touch-skin receptors, hearing, stretch of a muscle, receptors in vessel - blood pressure) • Chemoreceptors – activated by chemical substances (smell, taste) • Thermoreceptors – activated by heat or cold • Photoreceptors – activated by light (vision) • Nociceptors – activated by intense stimuli of any type that result in tissue damage, produced sensation is pain Stimulus a change in external or internal environment (a form of environmental energy) that stimulates the receptor adequate stimulus - type of stimulus (energy) that a receptor is specialised for - receptors are specialised on one type of energy (except nociceptors): light – vision chemical substances – smell, taste, etc. - even if a receptor can be stimulated also by other type of energy, it is most sensitive to the adequate stimulus, i.e. to a small intensity of stimulus (minimum) threshold intensity of a stimulus – minimum strength of a stimulus that triggers an action potential in the sensory neuron's axons (i.e. it is the weakest stimulus that can be reliably detected) receptor potential - a change in membrane potential a of a sensory receptor - graded response depending on the strength of the stimulus - is spread with a decrement - if sufficiently strong to reach axon, it is transduced by a nerve as action potential Sensory nerve • conducts nerve impulses to central nerv. system • usually 3 neurons form a sensory pathway Central nervous system • sensory projection - brain centres for individual senses • primary cortex (for vision, hearing...) – I can see, hear...something • secondary cortex – I can recognize what I see..hear • tertiary cortex (association) – complex sensation (colour+shape+taste+memories) Response to a sensory stimulus 1. reflex – quick, stereotype, involuntary response to a stimulus 2. conscious behaviour (voluntary motor activity, memory, etc.) http://t2.gstatic.com/images?q=tbn:ANd9GcQLxYEdEk8lR TuToHhhLhGTIAOfpOUYUkXwbLaC9dD3FYcpm2XA Sense of hearing - The ear Sound • • • • • vibrations (compression/decompression) of air (water or solids) audible frequency: 20 – 20 000 Hz (Hertz) adequate stimulus for sense of hearing pitch – determined by frequency of the waves loudness determined by height of the waves Pitch • high tone • deep tone Loudness • quiet sound • loud sound - the acoustic waves exert pressure - decibel – unit of loudness (derived as logarithm of acoustic pressure) 0 dB – threshold of hearing - less sensitive people – slightly above 0 dB, - people with very sensitive sense of hearing – can detect even negative dB 60 dB – speech > 100 dB – damage of the ear > 120 dB – pain • sensitivity of the ear to sound depends on the frequency of sound waves • maximum sensitivity is in the range 1000 - 4000 Hz (frequency of speech) = threshold ~ 0 dB • the ear is less sensitive to lower and higher frequencies than 1000-4000 Hz • the more higher /lower frequency - the louder the sound must be in order to be detectable Function of the external ear • auricle (pinna) – captures the sound waves and gives them appropriate direction • ear canal – conducts the sound • tympanic membrane – separates external ear from middle ear – sound causes its oscillation http://www.neuroreille.com/promenade/english/ear/exear/e_oreille_ext.gif Function of the middle ear - cavity in os petrosum, filled with air - chain of 3 ossicles - malleus - hammer - incus - anvil - stapes – stirrup - malleus is connected to the eardrum - stapes is connected to oval window (membrane separating middle/inner ear) - ossicles transduce the sound from outer into the inner ear and amplify it: - area (eardrum/oval window) pressure amplification - hearing is improved by approx 25 dB http://www.ohiohealth.com/mayo/images/image_popup/ans7_inside_ear.jpg - m. stapedius, m. tensor tympani - loud sound causes their reflex contraction - dampen movements of the ossicles - protect the ear - middle ear - communicates with pharynx by Eustachian tube - balance of pressure on both sides of the eardrum (e.g. in airplane) - risk of infection spreading !!! - from nasopharynx into middle ear - easily in children Function of inner ear Components: • cochlea – sense of hearing • vestibule, semicircular canals – sense of balance Cochlea • a spiral shaped organ (2 ¾ turns) • inside - organ of Corti with sensory receptors - hair cells http://www.nidcd.nih.gov/staticresources/images/electrode_array.jpg http://www.ohiohealth.com/mayo/images/image_popup/ans7_inside_ear.jpg Inner ear - 3 chambers A/ bony labyrinth - filled with fluid - perilymph 1. scala vestibuli 2. scala tympani B/ membranaceous labyrinth - scala media - filled with fluid - endolymph Reissner´s membrane – separates scala vestibuli from scala media Cross-section through one of the turns of cochlea Basilar membrane – separates scala tympani from scala media Inside scala media • organ of Corti • receptor cells = hair cells, their cilia are covered by tectorial membrane https://ccrma.stanford.edu/realsimple/psychoacoustics/img5.png • sound waves cause fluid movement in scala vestibuli • fluid movement is transduced into the fluid of scala media and s.tympani • basilar membrane (soft) and tectorial membrane (rigid) become displaced • this causes cilia to move – this movement elicits receptor potential https://ccrma.stanford.edu/realsimple/psychoacoustics/img5.png http://www.colorado.edu/intphys/Class/IPHY3730/image/10-21.jpg Cochlea „unfolded“ - tones produce travelling wave on basilar membrane - the farther from oval window – the less stiff the membrane - the wave travels to the point with maximum resonance (then dies out) - the higher the tone the closer the maximum resonance point • low tones/low frequencies - maximum resonance close to apex • middle frequencies - middle of the basilar membrane • high frequencies - max resonance close to the oval window Air conduction of sound - normal sound transmitting in healthy people • external ear • middle ear • internal ear Bone conduction of the sound • sound causes vibration of bones – os petrosum • vibration of the bones is transmitted directly to inner ear • significant way of sound transmitting if the air conduction does not work properly (e.g. inflammation of the middle ear) • higher threshold – louder sound necessary in order to hear Central auditory pathway - we can hear the soud when signal (AP) arrives to brain cortex 1. cochlear afferent fibres = n. statoacusticus - synapses in ventral and dorsal cochlear nuclei (med.oblongata/pons) 2. synapse in superior olive (med. oblongata/pons) lemniscus lateralis (ipsi, contra) to colliculi inferiores (midbrain) 3. corpus geniculatum mediale (thalamus) =radiatio acustica cortex – temporal lobe - primary auditory cortex - secondary auditory cortex - tertiary cortex (association) Otoscopy - examination of external ear Principle - examination of ear canal and eardrum using otoscope - otoscope – a device with speculum (ear mirror) and light source that is inserted into ear canal - ear canal and eardrum is visually examined Procedure: - the patient is sitting sideway – better access to ear - switch the light in otoscope on - pull the auricle – to lateral + cranial + dorsal direction – the ear canal is straightened - insert slowly speculum of the otoscope into the ear - observe the appearance of ear canal and eardrum (light reflex, try to distinguish imprints of malleus - stria mallearis and prominentia mallearis) Results describe your observation: - skin of ear canal – pink/ red, inflamed with rash - presence of cerumen (yellow wax) – normal/excessive quantity - presence of pus, blood - appearance of the eardrum smooth, grey/red-inflamed, perforated Conclusion: is the result of examination normal? Ear tests with tuning forks Examination of • air conduction of sound • bone conduction of sound Allow to distinguish 1. conduction disorders - external ear - middle ear 2. perception disorders - inner ear - sensory pathway - brain centre for hearing Rinné test • sound a tuning fork with a hammer • place it on the processus mastoideus of the patient (bone conduction) • in the moment as the patient stops to hear the sound, put the fork at patient's pinna (air conduction) • in case that the patient cannot hear sound, repeat the test in reverse order http://www.aafp.org/afp/20000501/2749_f4.jpg • record the time – of bone conduction (BC) - how long could the patient hear a sound conducted by bone – of total conduction (TC) how long could the patient hear a sound conducted by bone + air Normal result: TC:BC = 2:1 Abnormal result: BC>AC AC= BC Rinné positive (R+) Rinné negative (R-) Rinné inconclusive (R±) Schwabach test • sound a tuning fork • place it on the processus mastoideus of the patient • in the moment as the patient stops to hear the sound, put the fork on processus mastoideus of the doctor • normally the doctor should not hear any sound • repeat the test in reverse order (doctor-patient) • normally the patient should not hear any sound patient Normal result: • Schwabach normal Abnormal result: • Schwabach shortened – the patient can hear the sound for shorter time then the doctor • Schwabach prolonged – the patient can hear the sound for longer time then the doctor doctor http://www.aafp.org/afp/20000501/2749_f4.jpg Weber´s test • sound a tuning fork • put it in the middle of the patient´s forehead • the patient is asked to say on which side he can hear the sound louder (right, left) http://www.aafp.org/afp/20000501/2749_f4.jpg Normal result: • the loudness is the same on both sides (←W→) Abnormal result: • louder at one side = lateralization • e.g. if louder on the right = lateralization to the right • Conclusion: Resume and evaluate results of all tests together normal hearing conduction disorder perception disorder R+ R- R+, R± Schwabach normal Schwabach prolonged Schwabach shortened ←W→ W lateralization to the sick side W lateralization to the healthy side Audiometry Principle • sensitivity of the ear to sound depends on the frequency of sound waves • maximum sensitivity is in the range 1000 - 4000 Hz (frequency of speech) = threshold ~ 0 dB • the ear is less sensitive to lower and higher frequencies than 1000-4000 Hz • the more higher /lower frequency - the louder the sound must be in order to be detectable Procedure • each ear is examined separately • air conduction / bone conduction of sound can be examined • patient is not allowed to watch the audiometer (sitting backwards to it) • put earphones on the patient´s ears (only one is active) • give a switch to the patient´s hand • preset the frequency in audiometer to the lowest value • preset the intensity in audiometer to the lowest value • slowly move the marker for intensity to higher values • • • when the patient hears the sound, he/she gives a sign by pushing the switch – light flash is seen on audiometer the value of intensity indicates the threshold for that particular frequency record the threshold intensity in dB into the sheet (dot) • • repeat the procedure within the predetermined range of intensity repeat the whole examination for bone conduction Results • by connecting the dots draw a graph and evaluate it The vestibular system part of the inner ear contributes to balance, sense of spatial orientation provides input about movement Components 3 semicircular canals - detect rotation of the head saccule and utricle - detect linear movement of the head http://t1.gstatic.com/images?q=tbn:ANd9GcTgpLH6l2qvF W-q8XnnW4JySSBX0RZif93UqMz5of6l-oeOYLDobg • semicircular canals, utricle, saccule – filled with liquid - endolymph • sensory cells – hair cells http://images.suite101.com/2476145_com_innerear4.jpg Linear acceleration • areas with sensory cells – macula utriculi – macula sacculi • both maculas contain hair cells covered by gelatinous substance (cupula) containing otolits (earstones) • when moving – gel with otolits moves the hair cells to side – this elicits action potential Angular acceleration • 3 semicircular canals – horizontal – posterior – superior • at right angles to each other – cover all 3 planes http://t1.gstatic.com/images?q=tbn:ANd9GcTgpLH6l2qvFWq8XnnW4JySSBX0RZif93UqMz5of6l-oeOYLDobg • ampulla – a swelling on the beginning of each canal • crista ampullaris - contains hair cells • as the body starts to rotate endolymph inside canals starts to move • hair cells are stimulated by the movement of endolymph – action potentialis elicited http://image.absoluteastronomy.com/images/encyclopediai mages/v/ve/vestibular_pushpull.svg.png Examination of nystagmus in a human Nystagmus • movement of eyeballs – fast movement to one side – slower movement to the other side • reaction to stimulation of vestibular apparatus (canales semicirculares) by rotation and by movement of endolymph • signals from the vestibular system trigger eye (and head) movements to stabilize the visual image on the retina • it may be caused also by other stimuli • sign of some neurological disorders http://ivertigo.net/graphics/v4.gif Principle • rotation causes movement of endolymph – in the direction of movement • movement of endolymph is a stimulus for hair cells in vestibular organ • endolymph moves with delay, it reaches the speed of movement of the body only in a few seconds • at the beginning of rotation – due to delayed movement of endolymph, the hair cells are temporarily bent to the opposite side to movement – within this time perrotation nystagmus occurs • after the rotation stops – endolymph continues to move – hair cells are temporarily bent to the direction of movement – postrotation nystagmus occurs until endolymph stop • the direction in which the endolymph is moving – is the same as the slow movement of eyeball • the direction of nystagmus is determined according to the fast movement (to the right, to the bottom, etc.) • i.e. after rotation movement nystagmus to the opposite side to direction of movement can be observed Procedure • the examined person is seated into a rotating chair and belted with head in normal position (to stimulate the horizontal canal) • the chair is set into rotation (for approx 20-30 sec, as fast as possible) • the rotation is suddenly interrupted • the nystagmus is observed (lasts just a few seconds) • the examination is repeated in position with head leaned 1. towards the arm 2. to the front Result: nystagmus – direction Conclusion: explain your observation