Transcript The Senses
The Senses
Terminology
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
Ex: hearing, seeing, tasting, touching, smelling
To feel a sensation…
1.
2.
3.
4.
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…
General
Touch
Pressure
Temperature
Pain
Position
Special
Smell (olfaction)
Hearing &
Equilibrium
Seeing (vision)
Tasting (gustation)
Classification of Sensations…
Be familiar with…
Mechanoreceptor (movement) = detect
touch, pressure, hearing
Thermoreceptor (temperature) = detect
temperature changes
Photoreceptor (light) = detect light changes
Chemoreceptor (chemicals) = detect taste &
smell
Cutaneous sensations (tactile)
Are general senses
Senses that affect skin
Receptors embedded in dermis
Touch
Crude = perception of touch
Fine = specific information about touch
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
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
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
Special Senses
Have an organ devoted to the sense
Ear = hearing & equilibrium
Eye = vision
Nose = olfaction
Tongue = gustation
Vision
Uses more than half of the sensory
receptors in the body
Accessory structures:
Eyebrows & eyelashes = protection
eyelids = protection & spread secretions
Lacrimal glands = produce tears that
contain lysozyme (bactericidal enzyme)
Vision specialists
Opthalmology: study of eye structure, function,
and diseases
Optician
Optometrist
Fits & adjusts lenses
Optician duties +
Gives eye exams, corrective lens prescriptions
Opthalmologist (M.D.)
Optometrist duties +
Surgical procedures & medication prescriptions
The Eye (p. 278, Figure 10.17)
2.5 cm in diameter
Exterior has 3 layers (coats = tunics)
Outer = fibrous tunic
Middle = vascular tunic
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
Lines posterior ¾ of eye; contains photoreceptors (rods = b/w &
cones = color)
Optic disk = blind spot found here
The Eye
The Eye Chambers
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
More on the eye
Binocular vision: seeing 1 image with 2 eyes
The eye works like a camera
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
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
Gustation
Sense of taste
Uses the tongue (and nose)
4 classes of taste
Sweet (tip)
Salty (sides, anterior)
Sour (sides, posterior)
Bitter (back)
Gustation continued
Taste buds
~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
Static: maintenance of body position
Dynamic: correction of body position
Both use the crista (hair cells) in the ear
The Ear
3 main regions
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
The Ear continued
Middle ear: air-filled cavity between ear drum
and internal ear
Ossicles located here
Malleus, incus, stapes
Internal ear
Outer bony labyrinth
Cochlea (H), vestibule (E), semicircular canals (E),
perilymph fluid
Inner membranous labyrinth
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
20-20,000 Hertz (Hz) in pitch (frequency)
0-90 decibels (dB) in intensity (loudness)
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