Sensation: Part 2

Sensation: A Deeper Look into the SensesTransmission of Sensory InformationTransduction: Transformation of stimulus energy to the electrochemical energy of neural impulsesImpulses from sense organ travel to the thalamus before the cortexExcept for smell which goes straight to the olfactory bulbs (underside of the cortex)Job of the cortex: To put all the information together and make sense of it and then puts it into actionVision: Occipital lobeHearing: Temporal lobeBody senses: Parietal lobesTaste: Where the temporal and parietal lobes meetSmell: Lower portion of the frontal lobe

VisionPhotoreceptors: Modified neurons that convert light energy into electrochemical neural impulses which include:Rods: Detect black, white, and gray and also detect movement. Important for peripheral and dim-light vision when cones do not respond.Have a lower threshold than conesLocated in the retina except in the foveaCones: Detect color and fine detail in daylight or in bright-light conditions. Located mostly in the fovea; none in the periphery.

Problems with VisionNear-sighted: Closer objects are seen clearer than distant objectsToo much curvature of the cornea and/orLens focuses an image in front of the retinaFar-sighted: Distant objects are seen more clearer than close objectsToo little curvature of the cornea and/orLens focuses the image behind the retinaAstigmatism: Distorts and blurs image at the retinaCaused by an irregularity in the shape of the cornea and/or the lens

Color BlindnessTrichromatic Theory: Proposed mechanism for color vision with cones that are differently sensitive to different wavelengths of light; each color you see results from a specific ratio of activation among the three types of receptorsProposed by Thomas Young & Hermann von HelmholtzTrichromats: three types of cones (red, green, blue)Dichromats: combination of two types of conesMonochromats: one type of coneThose that are colorblind lack the chemical usually produced by one or more types of conesRed & green blindness caused by a defective gene on the x-chromosome (sex-linked recessive traitmore common in males)Blue & yellow and total color-blindness are rareOpponent-Process TheoryProposed mechanism for color vision with opposing retinal processes for red-green, yellow-blue, white-black. Some retinal cells are stimulated by one pair and inhibited by anotherProposed by Ewald HeringHelps explain why mixing complementary colors such as red and green produces the perception of white and the appearance of negative afterimages.How We SeeThe light from the outside world travels to your eye.The light then enters the eye through the pupil and travels to the cornea.The cornea focuses the light upon the lens.The lens further focuses the light on the retina. The image is flipped over and spread across the back of the retina. The retina then carries the light signals to the brain via the optic nerve.

Audition (Sound)The loudness of a sound is determined by the amplitude (height) of the sound wavesMeasured in decibels (dB)Absolute threshold for hearing is 0 dBnormal conversations 60 dBFrequency: The number of complete wavelengths that pass a point in a given amount of time. Wavelength is proportional to the frequency. Determines the hue of light or the pitch of soundHertz HzPitch: Highness or lowness of a sound. Shorter wavelength, the higher frequency and the higher the pitch.Timbre: The quality of a sound determined by the purity of a waveform. What makes a note of the same pitch and loudness sound different on different musical instruments.What did you say?Conduction deafness: Loss of hearing due to a punctured eardrum or if any ossicles lose their ability to vibratePeople can hear the vibrationsHearing aids help amplify the vibrationsNerve (sensorineural) deafness: Loss of hearing that results from damage to the cochlea, hair cells, or auditory neurons Causes may include disease, biological changes (aging), or constant exposure to loud musicCochlea implants translate sounds into electrical signals which are wired into the cochlea's nerves

http://www.youtube.com/watch?v=0ZcZVugtF6w

Localization of SoundsBecause we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound.

10Localization of Sound1. Intensity differences2. Time differences

Time differences as small as 1/100,000 of a second can cause us to localize sound. The head acts as a shadow or partial sound barrier.Sound TheoriesPlace Theory: The position on the basilar membrane at which waves reach their peak depends on the frequency of a tone. Accounts well for high-pitched soundsHigh frequencies produce waves that peak at the close end and the opposite is true for the low frequencies (peak at far end)Proposed by Georg von BekesyFrequency Theory: The rate of the neural impulses traveling up the auditory nerve matches the frequency of a tone, enabling you to sense its pitch. Combination of the place theory and the frequency theory helps explain hearing intermediate-range pitchesVolley Principle: Neural cells can alternate firing can achieve a combined frequency of about 4,000 times per second.Combination of the frequency theory and volley principle helps explain how you hear low-pitched sounds

How We HearNoise is collected by the outer ear or pinnaThe sound waves travel along the ear canal to the ear drum.When the sound waves hit the ear drum they make it vibrateThe hammer, anvil and stirrup are the smallest bones in your body. Vibrations by the ear drum cause the 3 bones to vibrate in turn.As the stirrup vibrates, it causes vibrations in the fluid of the cochlea.The mechanical vibrations in the fluid of the cochlea bend the thousands of tiny delicate hair cells known as cilia. Then the vibrations change into electric nerve impulses.The auditoria nerve then carries these electric impulses to the brain.The brain translates the sounds it receives so that they have meaning for us.

With what we have discussed thus far about sensations (and using your own personal experiences), of the 6 senses which one would you GIVE UP and which one would you be reluctant to live without?Justify your response!Touch

The sense of touch is a mix of four distinct skin sensespressure, warmth, cold, and pain.

Bruce Ayers/ Stone/ Getty Images15Preview Question 10: How do we sense touch and feel pain? Touch is both the alpha and omega of affection (James, 1890).Skin SensesOnly pressure has identifiable receptors. All other skin sensations are variations of pressure, warmth, cold and pain.

Burning hot

PressureVibrationVibrationCold, warmth and pain16SomatosensationGeneral term for the four classes of tactile (touch) sensations:Touch/pressure (tickling)WarmthColdPain (itching)Other sensations result from a combination of stimulation from multiple receptors:Burning: Warmth, cold, and painWetness: cold and pressure

PainPain tells the body that something has gone wrong. Usually pain results from damage to the skin and other tissues. A rare disease exists in which the afflicted person feels no pain.

Ashley Blocker (right) feels neither painnor extreme hot or cold.AP Photo/ Stephen MortonGabby18Gate-Control TheoryMelzack and Wall (1965, 1983) proposed that our spinal cord contains neurological gates that either block pain or allow it to be sensed.Small nerve fibers conduct most pain signals. Stimulating large nerve fibers closes the spinal gate.

Gary Comer/ PhototakeUSA.com19One way to treat chronic pain is to stimulate it through massage by electrical stimulation or acupuncture. Rubbing causes competitive stimulation to pain thus reduces its effect.Pain ControlPain can be controlled by a number of therapies including, drugs, surgery, acupuncture, exercise, hypnosis, and even thought distraction.

Todd Richards and Aric Vills, U.W. Hunter Hoffman, www.vrpain.com

20Burn victims can be distracted by allowing them to engage in illusory virtual reality. Their brain scans show differences in pain perceptions.Smell

Like taste, smell is a chemical sense. Odorants enter the nasal cavity to stimulate 5 million receptors to sense smell. Unlike taste, there are many different forms of smell.21Preview Question 12: How does our sense of smell work?Smell and MemoriesThe brain region for smell (in red) is closely connected with the brain regions involved with memory (limbic system). That is why strong memories are made through the sense of smell.

22Sensory InteractionWhen one sense affects another sense, sensory interaction takes place. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor.TasteTraditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors for a fifth taste have been discovered called Umami.

SweetSourSaltyBitterUmami(savory)24Preview Question 11: How do we experience taste?Taste Buds

Taste is a chemical sense, like smelling. There are 5 basic kinds of taste: sweet, sour, bitter, salty and umami (savoriness), like the taste of monosodium glutamate. The spicy foods (like chili peppers) stimulate the pain receptors, not the taste buds. Body Position and MovementThe sense of our body parts position and movement is called kinesthesis. The vestibular sense monitors the head (and bodys) position.

http://www.heyokamagazine.comWhirling DervishesWire WalkBob Daemmrich/ The Image Works26Preview Question 13: How do our senses monitor our bodys position and movement?