Ability to detect + respond to stimuli is essential for survival as it allows execution of appropriate response E.g. when hand placed on hot surface, thermoreceptors detect stimulus (heat)+ initiate withdrawal of hand to prevent injury Environments contain different kinds of stimuli – hence, many organisms have a range of different, specialised receptor types Type of receptor Stimulus Organ Mechanoreceptor Mechanical stimuli, i.e. Sound Gravity Touch Pressure Hair cells (ear) Skin Thermoreceptors Temperature, i.e. Hot Cold - Skin Electromagnetic receptors Electromagnetic i.e. - Visible light - Eye (photoreceptors) - Ultraviolet - Infra-red - Pit organs (snakes) Chemoreceptors Chemicals Nose Tongue
process information from secondary sources to evaluate a hearing aid and a cochlear implant in terms of: the position and type of energy transfer occurring conditions under which the technology will assist hearing limitations of each technology Hearing aids and cochlear implants Hearing aid or cochlear implant can be used to improve hearing (depending on the type of hearing loss) Device Hearing aid Cochlea implant (bionic ear) Type of energy transfer Sound energy; Electrical energy Sound energy energy; Electrical energy Radio energy; Electrochemical energy Information Battery-operated electronic device that fits into the hollow just outside ear canal by amplifying sound waves within the ear canal (making them louder), increasing the energy being transmitted through the ear Consists of a: Microphone – receives waves + changes them into electrical energy Amplifier – makes signal stronger Receiver – changes electrical energy into sound energy Speaker – directs sound energy into auditory canal Works by bypassing the damaged area of the ear + stimulating auditory nerve directly Receiver surgically implanted into patient’s skull (fine wires attach receiver to cochlea) Microphone behind patient’s ear picks up sound + transfers it to speech processor (worn on belt or in pocket) Processor converts sound into a digital signal (electrical energy) Signal transmitted to transmitting coil which sends message as FM radio signal to cochlea implant (under the skin) Attached wires stimulate auditory nerve which transmits signal to brain Hearing condition Conductive hearing loss Profound hearing loss (deafness caused by damage to inner ear)
(deafness caused by damage to outer or middle ear; may be due to aging, noise strain, injury, infection, head trauma) Advantages Relatively cheap Easy to install (no surgery required) - Provides hearing to profoundly deaf people Limitations Will not restore normal hearing Don’t only amplify speech – amplifies all sounds in the environment (background noise) Need to adjust to sound level May cause pain Do not assist hearing in people with damage to inner ear or auditory nerve Cost – surgery is expensive + there are ongoing costs Requires an operation to be installed Potential post-operative side effects E.g. infection, droopy face, numb tongue Need to learn to interpret sounds (quality limited/different) Success of implant system limited by degree of damage to auditory nerve +/or auditory centre of brain (highly damaged nerve will be limited in its ability to respond to stimulation)