Transcript The Senses

The Senses
Terminology
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Sensation: conscious or subconscious
awareness of external or internal body
conditions
Adaptation: the ability of a stimulus to
decrease its sensation over a prolonged
period of time.
Proprioception: perception of body position
Kinesthesia: perception of body movement
Perceptions: conscious sensation that you
acquire with all of your senses
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Ex: hearing, seeing, tasting, touching, smelling
To feel a sensation…
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Stimulus must occur
Sensory receptor converts the stimulus
into an impulse
The impulse is conducted to the brain
(via sensory or afferent neuron)
Brain (control center) integrates the
impulse into a sensation (hot, pain, itch,
etc.)
A look at the pathway
Senses can be…
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General
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Touch
Pressure
Temperature
Pain
Position
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Special
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Smell (olfaction)
Hearing &
Equilibrium
Seeing (vision)
Tasting (gustation)
Classification of Sensations…
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Be familiar with…
Mechanoreceptor (movement) = detect
touch, pressure, hearing
 Thermoreceptor (temperature) = detect
temperature changes
 Photoreceptor (light) = detect light changes
 Chemoreceptor (chemicals) = detect taste &
smell
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Cutaneous sensations (tactile)
Are general senses
 Senses that affect skin
 Receptors embedded in dermis
 Touch
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Crude = perception of touch
 Fine = specific information about touch
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Cutaneous receptors
Meissner’s corpuscle: rapid adapting fine
touch receptor
 Hair root plexus: rapid adapting receptor
for detecting movement on skin
 Merkel disks: slow adapting receptor that
coincide with Meissner’s corpuscle
 Ruffini’s corpuscle: slow adapting
receptor for detecting stretching & limb
movement
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More cutaneous receptors
Pacinian corpuscle: pressure & vibration
 Nociceptors (free nerve endings): itch,
tickle, pain
 Cold receptors (epidermis): temperatures
between 50-105 degrees Fahrenheit
 Warm receptors (dermis): temperatures
between 90-118 degrees Fahrenheit
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Pain
Referred pain: pain usually felt on the
skin overlying the affected organ
 Phantom pain: pain felt in an organ or
limb that has been removed
 Analgesia: pain relief; blocks chemicals
that stimulate free nerve endings
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Special Senses
Have an organ devoted to the sense
 Ear = hearing & equilibrium
 Eye = vision
 Nose = olfaction
 Tongue = gustation
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Vision
Uses more than half of the sensory
receptors in the body
 Accessory structures:
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Eyebrows & eyelashes = protection
 eyelids = protection & spread secretions
 Lacrimal glands = produce tears that
contain lysozyme (bactericidal enzyme)
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Vision specialists
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Opthalmology: study of eye structure, function,
and diseases
 Optician
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Optometrist
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Fits & adjusts lenses
Optician duties +
Gives eye exams, corrective lens prescriptions
Opthalmologist (M.D.)
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Optometrist duties +
Surgical procedures & medication prescriptions
The Eye (p. 278, Figure 10.17)
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2.5 cm in diameter
Exterior has 3 layers (coats = tunics)
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Outer = fibrous tunic
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Middle = vascular tunic
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Cornea: transparent outer covering for bending light as it enters
eye; covered by conjunctiva
Sclera: white of the eye; gives eye its shape
Choroid: lines sclera
Ciliary body: secretes aqueous humor; alters lens shape
Iris: colored part of eye; regulates pupil (hole) size
Inner = retina
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Lines posterior ¾ of eye; contains photoreceptors (rods = b/w &
cones = color)
Optic disk = blind spot found here
The Eye
The Eye Chambers
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Interior eye (divided by lens)
Anterior cavity = contains aqueous humor
(watery substance that maintains corneal
shape); constantly replaced
 Posterior cavity = contains vitreous humor
(jelly-like fluid that holds retina in place);
never replaced
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More on the eye
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Binocular vision: seeing 1 image with 2 eyes
 The eye works like a camera
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Light is refracted (bent) as it enters
Image is inverted on retina
Brain reverses image to recognize it
Pathway: light  rods & cones  bipolar cells
 ganglion cells  optic nerve  optic
chiasm  optic tract thalamus  occipital
lobe of brain
The eye camera
Eye disorders
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Myopia: near sightedness
 Hypermetropia: far-sightedness
 Presbyopia: old-sightedness which is usually farsighted; acquired ~ 40 years
 Astigmatism: irregular curvature of cornea or lens
 Color-blindness: inherited inability to see certain colors
due to missing cones; males affected more often (sexlinkage)
 Cataracts: clouding of lens; may cause blindness
 Glaucoma: high or low anterior eye (ocular) pressure;
leading cause of blindness in the U.S.
Myopia
Hypermetropia
Glaucoma
Cataract
Olfaction
Sense of smell
 Uses the nose
 Receptors embedded in mucosa
 Pathway: olfactory receptors  olfactory
nerves  olfactory bulbs  olfactory
tract  temporal lobe of brain
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Gustation
Sense of taste
 Uses the tongue (and nose)
 4 classes of taste
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Sweet (tip)
 Salty (sides, anterior)
 Sour (sides, posterior)
 Bitter (back)
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Gustation continued
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Taste buds
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~10,000 on roof of mouth, tongue, and throat
Found inside of papillae (elevations on tongue)
Pathway: Chemicals dissolve in saliva 
enters taste pore  gustatory hair  gustatory
receptor cell  taste bud  facial,
glossopharyngeal, & vagus nerves medulla
 hypothalamus  thalamus  cerebral
cortex
Hearing & Equilibrium
Uses the ear
 2 types of equilibrium
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Static: maintenance of body position
 Dynamic: correction of body position
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Both use the crista (hair cells) in the ear
The Ear
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3 main regions
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External ear: collects sound waves
Auricle (pinna) : made of cartilage
 External auditory canal: connects auricle with
eardrum; hairs and cerumen for protection
 Tympanic membrane (ear drum): thin partition
between outer and inner ear; resonates with
sound waves
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The Ear continued
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Middle ear: air-filled cavity between ear drum
and internal ear
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Ossicles located here
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Malleus, incus, stapes
Internal ear
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Outer bony labyrinth
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Cochlea (H), vestibule (E), semicircular canals (E),
perilymph fluid
Inner membranous labyrinth
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Series of sacs & tubules
Endolymph fluid
A look at the ear
Sound Pathway
Auricle  eardrum  malleus  incus
 stapes  oval window  perilymph
 vestibule  endolymph  cochlea 
vestibulocochlear nerve  medulla
 Soundwaves are the stimuli that we
perceive as sound
 Healthy human ear hears
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20-20,000 Hertz (Hz) in pitch (frequency)
 0-90 decibels (dB) in intensity (loudness)
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Ear disorders
Otitis externa: outer ear infection a/k/a
swimmer’s ear
 Otitis media: middle ear infection; results
when bacteria from throat creeps up
Eustachian (auditory) tube and into ears
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