1. The Senses

2. Stimulation of Senses
All sense organs must be able to detect a stimulus in the environment
Depending on the stimulus, a different receptor will be activated
Signal is transmitted to the brain

3. Types of Receptors Photoreceptors – light Chemoreceptors – chemicals
Pain receptors – physical damage
Thermoreceptors – change in temperature
Mechanoreceptors – change in position

4. Chemical Senses: Taste and Smell
Receptors are chemoreceptors
Associated with food intake, influence flow of digestive juices, and affect appetite

5. Anatomy of the Tongue Papillae contain taste buds Types:
Filiform and Fungiform papillae
Small, all over the top and sides of the tongue
Circumvallate Papillae
Large, on the back of the tongue

6. Taste - Gustation
Chemoreceptors are found in taste buds found on the sides of the papillae
Taste bud consists of three types of cells:
Gustatory Cells: contain chemical receptors
Supporting Cells
Basal Cells: immature cells that grow into either gustatory cells or supporting cells

7. Taste Bud Anatomy
Gustatory hairs project through the taste pore to bring in chemicals from the mouth
Information then moves through the gustatory cells to sensory neurons

9. Smell
Chemoreceptorsthat allow for smell are found in the olfactory epithelium
Located in the nasal cavity

10. Olfactory Epithelium Anatomy
Three Types of Cells in Olfactory Epithelium:
Olfactory Cells
Supporting Cells
Basal Cells
Olfactory cells have
olfactory hairs that
extend out into the
nasal cavity and bind chemicals

11. How Smell Works Pathway:
Olfactory Hairs  Olfactory Cell  Olfactory Nerve Fibers  Olfactory Bulb in the Brain
Neurons connect directly into the brain from the nasal epithelium through the cribriform plate

13. The Ear
Two functions:
Hearing and Equilibrium
Physical forces from sound and movements stimulate the mechanoreceptors in the inner ear

15. External Ear
Made up of:
Auricle (aka Pinna) – appendage on side of head
External auditory canal – tube carries sound
Tympanic membrane - eardrum
Sound waves travel thru canal, strike the tympanic membrane and cause it to vibrate

17. Middle Ear (Tympanic Cavity)
Tiny cavity hollowed out of temporal bone
Also connects to the throat by Pharyngotympanic tube
Sore throat could spread to ear, causes middle ear infection
Contains three small bones called ossicles
Malleus (hammer), Incus (anvil), Stapes (stirrup)

18. Middle Ear Tympanic membrane  Malleus  Incus  Stapes  Oval Window
Oval window - small opening in inner ear covered by a membrane
Sounds cause tympanic membrane to vibrate, which is amplified by the ossicles
Causes movement of fluid in inner ear

19. Inner Ear Vestibule – Senses gravity Cochlea - Hearing
Circle in the middle that contains the oval window
Cochlea - Hearing
Snail shaped structure on one side of the vestibule
Semicircular Canal – Balance
Three circular structures on other side of the vestibule

20. Inner Ear Outer structure made of bony labyrinth Contains perilymph
There is an inner membrane within the perilymph called the membranous labyrinth
Contains endolymph and the Organ of Corti
Organ of Corti contains the mechanoreptors, so when the endolymph around it moves they are stimulated

21. Ear Disorders CONDUCTIVE DEAFNESS
Conditions in outer or middle ear blocks vibrations
NERVE DEAFNESS
Nerve impulse doesn’t make it to brain
Correction Cochlear Implant

22. Outer Layers of the Eye SCLERA (aka “whites of the eyes”)
Front has a transparent portion – Cornea
Conjuntiva – mucous membrane keeps eye moist
Lacrimal Gland – produces tears

23. Middle Layer of the Eye CHOROID
Contains dark pigment to prevent scattering of incoming rays of light
Made up of 2 involuntary muscles:
Iris: constricts and dilates pupil, the hole at the center of it
Ciliary Muscles: helps focus on objects

24. Inner Layer of the Eye RETINA Contains microscopic photorecepotors:
Rods – nightime vision, black and white
Cones – daytime vision, color
3 types detect color – red, green, blue
Surrounds fovea centralis – a depression that contains the most cones
Visual sharpness is obtained by focusing the image on the fovea centralis

25. Inside the Layers of the Eye
Fluid maintains intraocular pressure of eyeball
Aqueous Humor – fluid in front of lens
Vitreous Humor – Jellylike material in the posterior cavity
Lens – directly behind pupil
Elastic to allow change of shape

26. How You See

27. Disorders of the Eye

28. Focusing Problems
Myopia - Image focuses in front of retina, distant objects blurry
Hyperopia - Image focuses behind retina, close objects blurry
Astigmatism – Abnormal curvature of cornea or lens, fails to refract light properly

29. Focusing Problems

30. Eye Disorders CATARACTS
Lens becomes cloudy so less light enters the eye
GLAUCOMA
Aqueous humor not drained properly, intraocular pressure builds up, can cause blindness

31. Color Blindness Unable to distinguish certain colors
Occurs when cones are nonfunctional
Most common – red cones missing
Can’t distinguish red from green