The Incredible Human SensesThe Incredible Human Senses

Sensory ReceptorsSensory Receptors

General Sense General Sense Receptors Receptors (Somatic)(Somatic)

Detect touch, Detect touch, temperature, and temperature, and pain.pain.

Responsible for Responsible for maintaining internal maintaining internal homeostasishomeostasis

Receptors are Receptors are distributed all over the distributed all over the body.body.

Special Sense Special Sense ReceptorsReceptors

Vision, hearing, Vision, hearing, balance, taste and balance, taste and smell.smell.

Initiate reflexes to Initiate reflexes to keep homeostasiskeep homeostasis

AdaptationAdaptationWhen a stimulus acts on a receptor, a When a stimulus acts on a receptor, a

receptor potentialreceptor potential builds up. builds up.

The response is graded The response is graded based on the strengthbased on the strength of stimulus.of stimulus.

Many receptors will show Many receptors will show ADAPTATIONADAPTATION to to a repeated or continual stimulus. a repeated or continual stimulus. Receptor potential is reduced thus the Receptor potential is reduced thus the sensation is reduced or eliminated.sensation is reduced or eliminated.

Types of Receptors by LocationTypes of Receptors by Location

ExteroceptorsExteroceptors Aka cutaneous Aka cutaneous

receptorsreceptors Found in the skinFound in the skin

VisceroreceptorsVisceroreceptors Located around Located around

organsorgans Mediate hunger and Mediate hunger and

thirstthirst

ProprioreceptorsProprioreceptors Found in skeletal Found in skeletal

muscle, tendons muscle, tendons and jointsand joints

Respond to Respond to movement, movement, stretching and stretching and orientation.orientation.

Sensory ReceptorsSensory Receptors

Sensitive to light and Sensitive to light and colorscolorsEyesEyes

Sensitive to chemicals in Sensitive to chemicals in the air and food, pH and the air and food, pH and glucose levels in blood.glucose levels in blood.

Nose and taste budsNose and taste buds

Sensitive to touch, Sensitive to touch, pressure, muscle pressure, muscle stretching, sound, motionsstretching, sound, motions

Skin, skeletal muscles & Skin, skeletal muscles & inner earinner ear

FunctionFunctionLocationsLocationsTypeType

Detect variations in Detect variations in temperaturetemperature

Skin, body core and Skin, body core and hypothalamushypothalamus

Everywhere except the Everywhere except the brainbrain

Signal danger, injury or Signal danger, injury or diseasedisease

Ex: itchingEx: itching

Classification by StructureClassification by StructureFree Nerve EndingsFree Nerve Endings Simplest and most Simplest and most

common receptorscommon receptors Most are nociceptors Most are nociceptors Create sensations such Create sensations such

as tickling, itching, touch as tickling, itching, touch and movement, heat and and movement, heat and cold.cold.

Can sense chronic or Can sense chronic or acute painacute pain..

Encapsulated Nerve Encapsulated Nerve EndingsEndings

They are They are mechanoreceptors that mechanoreceptors that are activated by being are activated by being “deformed”“deformed”

Respond to light and Respond to light and deep touchdeep touch

Some are resistant to Some are resistant to adaptation so that you do adaptation so that you do not lose a sense for what not lose a sense for what you are touching.you are touching.

Olfactory ReceptorsOlfactory Receptors Olfactory receptors are located Olfactory receptors are located

in the post superior portion of in the post superior portion of the nasal cavity and respond the nasal cavity and respond to chemicals dissolved in to chemicals dissolved in mucusmucus

Extremely sensitive to small Extremely sensitive to small amounts of chemicalsamounts of chemicals

Highly adaptive receptorsHighly adaptive receptors

Action potential travels from Action potential travels from nerves in thalamus to olfactory nerves in thalamus to olfactory cortex in braincortex in brain

Impulses linked to limbic Impulses linked to limbic system and system and hippocampus...memories!hippocampus...memories!

Olfactory PathwayOlfactory Pathway

Gustatory Sense (taste)Gustatory Sense (taste) Chemoreceptors on the tongue Chemoreceptors on the tongue

respond to testants (taste respond to testants (taste chemicals)chemicals)

Taste buds that house the Taste buds that house the chemoreceptors are located in chemoreceptors are located in the papillae on the tonguethe papillae on the tongue

Sweet, sour, bitter, and salty Sweet, sour, bitter, and salty are the primary tastesare the primary tastes

Metallic and umami Metallic and umami (meat/protein) are likely to be (meat/protein) are likely to be new tastes in the future.new tastes in the future.

Texture and temperature add Texture and temperature add to taste sensations.to taste sensations.

Adaptation usually occurs in a Adaptation usually occurs in a few minutes.few minutes.

Iris: Colored part of the eye, made of smooth muscles

Pupil: opening

Cornea: clear cover

Lens: focus objects

Ciliary Body: contracts and relaxes to modify the shape of the lens.

Posterior Cavity: filled with jellylike vitreous humor

Fovea centralis: depression in the macula lutea, highest concentration of cones, sharpest vision.Optic Nerve: impulses go to brain, optic disc known as blind spot

Blood Vessels

Choroid: highly vascular middle layer, modified into ciliary body and iris

Sclera: outer layer of eye, white part

Retina: inner layer, contains rods and cones, found only in posterior of eye

Ligaments: blend with elastic capsule that holds lens and connect with ciliary body

Anterior Cavity: filled with aqueous humor; has anterior and posterior chamber

Structures of the EyeStructures of the Eye

Neurons in the RetinaNeurons in the Retina*Listed in order in *Listed in order in which impulses which impulses are transmittedare transmitted

PhotoreceptorsPhotoreceptors Rods- detect light, Rods- detect light,

most numerous most numerous Cones- specialized Cones- specialized

to detect color, to detect color, highly concentrated highly concentrated in foveain fovea

Bipolar neuronsBipolar neuronsGanglion neuronsGanglion neurons

View of the eye View of the eye through the through the pupilpupil

Muscles of the EyeMuscles of the Eye

Extrinsic muscles- voluntary connect eye to bone; most active muscles in the body

Intrinsic muscles- iris and ciliary are involuntary muscles to control pupil size and lens shape respectively.

Accessory StructuresAccessory Structures

Eyebrows & eyelashesEyebrows & eyelashes offer protection offer protection from foreign objectsfrom foreign objects

EyelidsEyelids are covered by a thin layer of are covered by a thin layer of mucosa called conjunctiva which mucosa called conjunctiva which also covers the eye.also covers the eye.

Infection of conjunctiva is called Infection of conjunctiva is called pinkeye.pinkeye.

TearsTears

Lacrimal Apparatus-Lacrimal Apparatus- tears form in the tears form in the lacrimal glands and lacrimal glands and enter the eye from the enter the eye from the top outer corner. top outer corner.

Normally tears drain Normally tears drain through the through the lacrimal lacrimal canalscanals (tear ducts) (tear ducts) into the nasal cavity.into the nasal cavity.

VisionVision

Four processes must occur to form a clear imageFour processes must occur to form a clear image

1.1. Refraction-Refraction- light must pass through cornea, light must pass through cornea, aqueous humor, lens and vitreous humor.aqueous humor, lens and vitreous humor.

2.2. Accommodation of lens-Accommodation of lens- curvature of lens curvature of lens must change to increase refraction.must change to increase refraction.

3.3. Constriction of pupil- Constriction of pupil- prevents divergent prevents divergent rays from entering eye and blurring image.rays from entering eye and blurring image.

4.4. Convergence of eyes- Convergence of eyes- muscles move eyes muscles move eyes so that image falls on corresponding points so that image falls on corresponding points in the retinas.in the retinas.

Ciliary Muscles and Lens ShapeCiliary Muscles and Lens Shape

ContractionContraction Loosens ligaments and Loosens ligaments and

allows lens to bulge. allows lens to bulge. Allows for near visionAllows for near vision Prolonged use of near Prolonged use of near

vision tires the muscles vision tires the muscles and causes eye strainand causes eye strain

Aging of the lens prevents Aging of the lens prevents bulging resulting in bulging resulting in presbyopiapresbyopia

Vision DisordersVision Disorders

Myopia- nearsighted, cannot see far away. Myopia- nearsighted, cannot see far away. Eyeball is elogated.Eyeball is elogated.

Hyperopia- farsighted, cannot see up Hyperopia- farsighted, cannot see up close. Eyeball is short.close. Eyeball is short.

Presbyopia- cannot see upclose because Presbyopia- cannot see upclose because of aging of the lens.of aging of the lens.

Astigmatism- irregular curvature of the Astigmatism- irregular curvature of the cornea.cornea.

PhotopigmentsPhotopigments

RodsRods Photopigment rhodopsin is highly sensitive to light causing it to Photopigment rhodopsin is highly sensitive to light causing it to

break downbreak down This changes the membrane potential of the rod thus transmitting a This changes the membrane potential of the rod thus transmitting a

signal.signal. Images are seen in shades of gray when viewed only with rods.Images are seen in shades of gray when viewed only with rods.

PhotopigmentsPhotopigments

ConesCones There are three There are three

types if cones types if cones used to detect used to detect red, green and red, green and blueblue

Cone Cone photopigments photopigments are less sensitive are less sensitive to lightto light

Optical IllusionsOptical Illusions

Imagine the Imagine the Hermann Hermann Grid as a Grid as a map of city map of city streets; most streets; most intersections intersections appear to be appear to be grey, but grey, but when you when you look closely look closely at any at any individual individual intersection, intersection, you will see you will see that it is that it is white. The white. The streets, on streets, on the other the other hand, hand, appear white appear white no matter no matter where you where you look.look.

Optical Illusions Hermann GridHermann Grid

Optical Illusions Complemtary colorsComplemtary colors

Stare at the center of the flag for at least 20 second - even longer to enhance the effect - and then look at the white area such as a

light colored wall, or a white piece of paper.

How many F’s are there?How many F’s are there?

FINISHED FILES ARE THE RE SULT OF YEARS OF SCIENTI FIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS...

Instructions: Close your left eye and fixate your right eye on the cross in the first diagram. If your eye is about 12 inches (30 cm) away from the monitor, you should notice that the round dot disappears. This distance may vary according to the screen resolution you have set.

You may be surprised to see that the dot is replaced, not by a black region, but rather blank white space. The brain simply "fills in" the most probable stimulus (in this case, a uniform white area) where there is none. The following examples demonstrate the "filling-in" phenomenon in greater detail. Apply the same instructions as given above and you should notice the red markings each time are replaced by the most probable pattern that your brain is able to perceive. 

Smell and TasteSmell and Taste

Scent particles are actually Scent particles are actually chemicals detected by your chemicals detected by your nosenose

Scents are closely tied to Scents are closely tied to memories memories

Taste buds are the receptors Taste buds are the receptors found in your mouthfound in your mouth

TouchTouch

Sense of touch is not limited to one part of the bodySense of touch is not limited to one part of the body

Skin is our largest sense organ Skin is our largest sense organ

Greatest amount sense receptors are found in our fingers, toes Greatest amount sense receptors are found in our fingers, toes and face.and face.

The EarThe EarSense of Hearing and BalanceSense of Hearing and Balance Outer EarOuter Ear

Auricle or pinna(ear)Auricle or pinna(ear) Auditory meatus(ear canal)Auditory meatus(ear canal) Tympanic membrane(ear Tympanic membrane(ear

drum)drum) Middle EarMiddle Ear

Malleus(hammer)Malleus(hammer) Incus(anvil)Incus(anvil) Stapes(stirrup)Stapes(stirrup) Eustachian tubeEustachian tube

Inner EarInner Ear VestibuleVestibule CochleaCochlea Semicircular canalsSemicircular canals

Sense of HearingSense of Hearing

SoundSound is the result of is the result of vibrationsvibrations occurring in occurring in air, fluid and solid air, fluid and solid materialmaterial

Pathway of SoundPathway of Sound

auditory meatus

tympanic membrane

malleus(hammer)

incus(anvil)

stapes(stirrup)

oval window

cochlea

cochlear nerve

Sense of BalanceSense of Balance VestibuleVestibule

Utricle and saccule function Utricle and saccule function in static equilibriumin static equilibrium

Receptor hairs respond to Receptor hairs respond to movement of otoliths (ear movement of otoliths (ear stones)stones)

Sense of acceleration, Sense of acceleration, gravitygravity

Semicircular canalsSemicircular canals Flow of endolymph fluid Flow of endolymph fluid

triggers receptor hairs in triggers receptor hairs in canalscanals

Three canals are form right Three canals are form right angles to each other.angles to each other.

TinnitusTinnitus

An abnormal ringing noise in the ear most An abnormal ringing noise in the ear most commonly a ringing. It can be continuous or commonly a ringing. It can be continuous or intermittent. intermittent.

CausesCauses TumorsTumors DiseaseDisease Muscle spasmsMuscle spasms MedicationsMedications Loud noiseLoud noise