Sensation and Perception Hearing, touch, smell

Hearing

 Audition: energy form is sound waves – slower range of speeds, but work similar to sound waves  Pitch: how high or low sound is  Timbre: complexity of tone (instrument variations)  Decibels: measurement of the intensity of the sound – above 130 they are painful (siren, shot gun blast, jet airplane on runway, FULL VOLUME HEADSET!)  Sleep is disturbed by noise at about 70 decibels; soothing with a continuous sound around 50 decibels

 Shape of ear has a purpose – cupped design of the outer ear catches the sound waves and funnels them toward the eardrum – piece of skin stretched tightly  Sound waves hit drum – it vibrates; this causes small bone to vibrate; this bone is attached to another bone and acts like a lever, causing it to vibrate; third bone is attached to a snail shaped unit (cochlea)  Key to hearing is small hairs called cilia – 20,000 hair cells are found in cochlea – we lose them as we age – tuned to different frequencies – respond to movement on only a trillionth of an inch  Electrical impulses go through auditory nerve to the brain where it is interpreted  Cells specialize – certain cells recognize important sound patterns – mothers tuned to sounds of children; newborns soothed by sound of mother’s voice  

Touch

 Skin contains three types of touch receptors or cutaneous – each sends message to brain  Pressure – pinpricks, bruises, bug crawling  Changes in temperature  Injury or poison – cause painful feelings like when we have a major cut or burn 

Smell

 Olfaction is sense of smell – most animal like of human senses – hard to define using words – but associate with emotional event and we never forget  Nasal cavity has layer of mucus imbedded with cilia – collect molecules of odor – sent to olfactory bulbs wich generate a code to send to brain  Most critical is conveying information about food heading to our mouths – smell more important than taste  Pheromones – used by animals to communicate sexual interest  

Taste

 Taste receptors work through chemical communication  Major receivers are taste buds (little red spots, rich in blood supply)  Mucus and saliva in mouth cleanse the buds – takes a while – think brushing your teeth and drinking orange juice  Four types of receptors – sweet, salt, bitter, sour (umami?) 

Salt needs  Necessary for survival – operates nerve cells, keeps body chemistry in balance, used for muscle contraction  Newborns don’t like salt, after few months, we crave it; tapers off as we age and then reappears later in life  Pregnant women often crave salt for the fetus

Sugar Needs  Most animals need sugar – newborns will actively seek it  Vital for energy to run body  Often put on food in restaurants to make us crave it (hamburgers at fast food chains)

Sourness and Bitterness  More than one type of bitterness detectors  Help us detect poisons – most are bitter in one way or another  Sourness is also a protective sense – spoiled food often tastes sour 