Sense Organs The first step in knowing

What does it mean to hear? Sound waves traveling through the air Changes in air pressure that result from vibration – Each vibration is called a cycle or sound wave

Every sound has its own pitch and loudness – Depends on frequency (cycle per second) – Low sounds low frequency – High sounds high frequency Examples – Woman’s voice=shorter vocal chords ; Man’s voice =longer vocal chords – Violin has shorter strings than a cello Human hearing 20 to 20,000 cycles per second; Dogs, dolphins hear more cycles What is frequency

What is sound? Determined by height (amplitude of waves) – Higher the amplitude the louder the sound – Softer sounds have less amplitude Measured in decibels (height of wave) Ear needs time to adjust to louder sounds Zero dB = absolute threshold for hearing – Ticking watch 20ft away 90 db beginnings of hearing loss can occur – Train whistle, lawn mower

Parts of the Ear Outer ear – pinna (outside of the skull) Middle ear – ear drum & bones (hammer, anvil, stirrup) Inner ear – cochlea (snail shape tube that contains fluid & neurons) – Moves in response to vibrations – Movement transmits neural impulses along auditory nerve to the brain

Hearing & deafness We locate sounds by repositioning the head & ears Sensorineural deafness – Damage to inner ear – Loss of neurons in cochlea – Result of disease or prolonged exposure to loud sounds – Can only be corrected if people have memories of sound Conductive deafness – Damage to middle ear – As long as auditory nerve is intact it is possible for most people to hear – Use hearing aid to increase amplitude (loudness)

Smell & Taste Odors are detected by receptor neurons in each nostril Info is sent via the olfactory nerve Taste has 4 qualities Sweet, sour, salty, bitter (umami=savory) Apples & onions taste similar, it is their odor that makes their flavors different Taste buds –receptor neurons Taste sensitivities can be inherited – Few people ever lose their sense of taste – You grow new taste buds throughout your life

Skin & Touch Skin senses are a combination of pressure, temperature & pain – Reduces stress & depression – Can help babies thrive Extremities and face more sensitive than thighs, calves, upper arms and shoulders Different receptors fire for cold & hot The more pain receptors in our skin, the more sensitive the area

How do pain messages travel? Pain in contact area ->spinal chord ->thalamus ->projected on to cerebral cortex -> brain registers sensitivity & location -> prostaglandins produce & transmit pain messages to the brain Ibuprofin & aspirin stop production of prostaglandins

Why we do or do not feel pain Gate Theory: rubbing or scratching sends competing messages with pain messages – Prevents some of the pain messages from getting through Phantom pain: people who lose a limb or loss of feeling have memories of pain that are activated by nerve endings near the location of the original injury

Vestibular Sense Vestibular sense tells you whether or not you are upright – Helps keep you balanced – Lets you know if you are falling Kinesthesis: sense that informs you about the position & motion of their bodies – Athletes and musicians typically have more kinesthetic sense than others