1. SPECIAL SENSES

2. Special Senses General Senses
receptors that are widely distributed throughout the body
skin, various organs, and joints
receive stimulation of touch, temperature, pain
Special Senses
specialized receptors confined to structures in the head
eyes and ears
Allow vision, hearing, equilibrium, taste, and smell

3. Senses Sensory Receptors
specialized cells or multicellular structures that collect information from the environment
stimulate neurons to send impulses along sensory fibers to the brain
Sensation
a feeling that occurs when brain becomes aware of sensory impulse
Perception
a person’s view of the stimulus; the way the brain interprets the information

4. Receptor Types Chemoreceptors
respond to changes in chemical concentrations
Pain receptors (Nociceptors)
respond to tissue damage
respond to intense stimuli of any kind
Thermoreceptors
respond to changes in temperature
Mechanoreceptors
respond to mechanical forces
touch/pressure
Photoreceptors
respond to light

5. Referred Pain
May occur due to sensory impulses from two regions following a common nerve pathway to brain

6. Special Senses
Sensory receptors are within large, complex sensory organs in the head
smell in olfactory organs
taste in taste buds
hearing and equilibrium in ears
sight in eyes

7. Sense of Smell Olfactory Receptors chemoreceptors
respond to chemicals dissolved in liquids
Olfactory Organs
contain olfactory receptors and supporting epithelial cells
cover parts of nasal cavity, superior nasal conchae, and a portion of the nasal septum
Sensory Adaptation
when an odor seems to fade away after you have been exposed to it

8. Olfactory Receptors

9. Sense of Taste-Gustatory Senses
Taste Buds
organs of taste
located on papillae of tongue, roof of mouth, linings of cheeks, and walls of pharynx
Taste Receptors
chemoreceptors
taste cells – modified epithelial cells that function as receptors
taste hairs – microvilli that protrude from taste cells; sensitive parts of taste cells

10. Gustatory Sense Organs

11. Tongue Map

12. Taste Receptors

13. Taste Sensations Four Primary Taste Sensations
sweet – stimulated by carbohydrates
sour – stimulated by acids
salty – stimulated by salts
bitter – stimulated by many organic compounds
Spicy foods activate pain receptors

14. Hearing
Ear – organ of hearing
Three Sections
External
Middle
Inner

15. External Ear Auricle External auditory meatus Tympanic membrane
Collects sounds waves
Flap on the side of the head
External auditory meatus
Ear canal
Carries sound to tympanic membrane
Terminates with tympanic membrane
Tympanic membrane
Ear drum
Vibrates in response to sound waves
Separates external from middle ear

16. Middle Ear Tympanic cavity Air-filled space in temporal bone
Three auditory ossicles
Vibrate in response to tympanic membrane
Malleus, incus, and stapes
Oval window
Opening in wall of tympanic cavity
Stapes vibrates against it to move fluids in inner ear

17. Auditory Tube Eustachian tube Connects middle ear to throat
Helps maintain equal pressure on both sides of tympanic membrane
Usually closed by valve-like flaps in throat
Pathway for infection

18. Inner Ear Three Parts of Labyrinths Cochlea Semicircular canals
Functions in hearing
Semicircular canals
Functions in equilibrium
Vestibule
Range of Human Hearing
20 – 20,000 vibrations per second

19. Sight Visual Accessory Organs Eyelids Lacrimal apparatus
Extrinsic eye muscles

20. Eyelid Palpebra Composed of four layers Orbicularis oculi - closes
skin
muscle
connective tissue
conjunctiva
Orbicularis oculi - closes
Levator palperbrae superioris – opens
Tarsal glands – secrete oil onto eyelashes
Conjunctiva – mucous membrane; lines eyelid and covers portion of eyeball

21. Lacrimal Apparatus Lacrimal gland lateral to eye secretes tears
Canaliculi
collect tears
Lacrimal sac
collects from canaliculi
Nasolacrimal duct
collects from lacrimal sac
empties tears into nasal cavity

22. Coats of the Eyeball - Outer Tunic
Cornea
anterior portion
transparent
No blood vessels
Sclera
posterior portion
opaque
protection

23. Middle Tunic Iris anterior portion pigmented controls light intensity
Ciliary body
anterior portion
pigmented
holds lens
moves lens for focusing
Choroid coat
provides blood supply
pigments absorb extra light

24. Anterior Portion of Eye
Filled with aqueous humor (thick watery substance

25. Lens transparent biconvex lies behind iris
largely composed of lens fibers
elastic
held in place by suspensory ligaments of ciliary body

26. Accommodation
changing of lens shape to view objects

27. Iris composed of connective tissue and smooth muscle
pupil is hole in iris
dim light stimulates radial muscles and pupil dilates
bright light stimulates circular muscles and pupil constricts

28. Inner Tunic Retina contains visual receptors - Rods and Cones
continuous with optic nerve
ends just behind margin of the ciliary body
composed of several layers

29. Posterior Cavity
Contains vitreous humor – thick gel that holds retina flat against choroid coat

30. Layers of the Eye

31. Visual Receptors Rods long, thin projections
contain light sensitive pigment called rhodopsin
hundred times more sensitive to light than cones
provide vision in dim light
produce colorless vision
produce outlines of objects
Cones
short, blunt projections
contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe
provide vision in bright light
produce sharp images
produce color vision

32. Rods and Cones