Sensation Chapter 4

Sir Isaac Newton English physicist Observed a ray of sunlight (white light) broken up into the colors of the spectrum when it passed through a glass prism

Sensory Systems We experience the world through Vision, hearing, taste, smell, and touch Allows us to process information

Receptors and Stimuli Eye – wavelengths of light Ear – vibrations of air molecules Nose –molecules in the air Tongue – chemicals in food Skin – pressure/ temperature

Absolute Thresholds The smallest amount of a stimulation necessary in order for it to be detected by our sensory system (VOCAB) Vision – see a candle flame from 30 miles away Hearing – hear a watch tick from 20 ft. away Taste – 1 tsp. of sugar in 2 gal. of water Smell – 1 drop of perfume in a 1000 sq ft. Touch – wing of a bee falling on your cheek, 1 cm

How do we perceive? Info. from the environment is taken in by the senses through receptors Receptors bring the info. to the brain Perception – organizes the information that we receive, so we can use it

How do we perceive? Sensations - based on stimuli from the environment Sensory coding - way the message is sent to the brain Through these codes, the brain then processes the information

Sensory Adaptation When a particular stimulus is received over a period of time, you adapt to the stimulus (VOCAB) Ex. When you are in a completely dark room, at first you can not see anything, then your eyes begin to adjust to the darkness and you can see

Vision and Light Light is the only form of electromagnetic radiation the human eye can see Other types of light are: Gamma rays Ultraviolet rays – move too slowly Infrared rays – move too quickly Radio waves

Vision and Light Visible light is white light from the sun or light bulb White light - different frequencies or wavelengths Different wavelengths = different colors Visible spectrum of colors violet (shortest) to red (longest)

Color Spectrum R O Y G B I V

How The Eye Responds to Light Light first enters the cornea (transparent covering of the eye) The image is then focused using the lens (behind the cornea) Light then passes through the pupil (dark area in the center of the eye) which is surrounded by the iris (colored part of the eye) The pupil dilates (gets bigger) in dim light The pupil contracts (gets smaller) in bright light

How The Eye Responds to Light The lens focuses the image on the retina (interior of the eye) by a process called accommodation. The retina consists of neurons called photoreceptors The photoreceptors convert light into electrical activity (bringing the info. to the brain). Rods – function in dim light Cones – function in bright light, color

How The Eye Responds to Light Optic nerve (where it leaves the eye) – no photoreceptors in this area (blind spot) The photoreceptors send impulses to the optic nerve, which sends them to the visual cortex of the brain, which then interprets the image

Color We see color because our eyes have different receptors for different wavelengths of light Hue (color) – refers to a particular wavelength Saturation – purity, richness, or intensity of color. (Red – high saturation, Pink – low saturation) Brightness – amplitude or height

Trichromatic Theory Trichromatic – 3 color theory 3 types of cones 1. Red 2. Green 3. Blue All colors result from a combination of these three

Opponent-Process Theory Three types of receptors: Each receptor is capable of responding to one of these, but not all 1. red-green 2. yellow-blue 3. black - white

Opponent-Process Theory The colors from each pair oppose each other, they cannot be blended The 4 primary colors (red, green, blue, yellow) can be mixed with colors from other pairs This mixing creates all the colors of the visible spectrum

Color Blindness Color weakness Affects 8% of the male population Less than 1% of the female population Usually inherited from the maternal grandfather

Hearing and Sound Sound is created in our brain from external stimuli An object generates sound waves when its vibrating causes vibrations in the air molecules around it Sound waves – patterns of vibrations Sound waves travel much slower than light waves

Hearing and Sound Sound waves are picked up by our auditory system - when the vibration puts pressure on our eardrum (this causes vibrations within the ear) When these impulses reach the brain, we interpret them as a specific sound

Characteristics of Sound 1. Pitch – how high or low a sound it 2. Timbre – quality/complexity of sound 3. Intensity – loudness of a sound, measure in decibels

Sound Waves and the Ear An object in motion will produce sound Sound waves travel in all directions You hear something when the sound wave (pattern of vibration) is detected by the receptors in the ear The brain then translates these receptors into sounds

3 Parts of the Ear 1. External – air conducts sound waves 2. Middle – bone conducts sound waves Hammer, anvil, stirrup (vibrations of these bones transmit sound to the inner ear) 3. Inner – fluid conducts sound waves Sound is transmitted in the cochlea (tube filled with fluid)

Auditory Nerve Conveys neural impulses to the hearing areas of the cerebral cortex Brain can determine where a sound is coming from

Deafness 1. Conduction Eardrums or middle ear bones do not vibrate Sound waves are partially or completely prevented from entering the inner ear Hearing aids help amplify sound waves so they can reach the inner ear

Deafness 2. Nerve Deafness 3. Stimulation Deafness damage to the auditory nerve Messages cannot reach the brain 3. Stimulation Deafness Permanent hearing loss Cochlea is damaged by prolonged exposure to very loud noise

Smell & Taste Chemical senses Receptors in the nose respond to molecules in the air Receptors for taste on the tongue and mouth respond to chemicals in foods

How do we taste food? Taste buds (receptors) are located on the surface of the tongue and roof of the mouth 4 Primary taste qualities 1. Bitter 2. Sour 3. Salty 4. Sweet

How do we taste food? The sense of smell is involved in experiencing taste

How do we smell? Receptors are located in the nose The process of olfaction (smelling) begins when we inhale A sensory code in the olfactory bulbs sends info. about the molecules to the brain

How do we smell? Animals use their sense of smell in selecting a mate At appropriate times their bodies give off pheromones – molecules that attract the opposite sex

Touch, Pressure, Temperature & Pain Somatic receptors Found all over the body Varies in different areas Tongue, lips, face, hands – the greater # of receptors the more sensitive to stimuli Pain receptors are also found inside the body

Pain Serves as a warning signal Provides us with vital information about an illness

Pain Thresholds vary with each individual Low tolerance High tolerance Never feel pain

How does the body alleviate pain? Various types of drugs Aspirin Tranquilizers Pain killers

How does the body alleviate pain? Endorphins (natural) Released by neurons in the upper spinal cord and several regions in the brain Bind receptors in the brain – just like pain killers do

Gate Control Theory Built in gating mechanism in the spinal cord Block neural impulses outside the brain 2 Types: Large (fast conducting) Small (slow conducting)

Gate Control Theory A message sent in one pain fiber can close the “pain gate” to a message from the other fiber If only one pain message gets to the brain – we feel less pain!

Acupuncture Ancient Chinese practice Needles are inserted in the appropriate places in the body that affect the functioning of pain gates When the doctor twirls the needles, this causes small, sharp pains, which, when carried by small fibers, close the gates to more intense or chronic pain.