Chapter 10

1. Chapter 10 Somatic and Special Senses

2. Sensory Receptors = detect environmental changes and trigger impulses that travel to central nervous system for interpretation • 2 major categories of sensory receptors: • 1. somatic senses = touch, pressure, temperature and pain • 2. special senses = smell, taste, hearing, equilibrium and vision 10.1

3. 5 Types of Receptors: 1. Chemoreceptors = changes in chemical concentration 2. Pain Receptors = detect tissue damage 3. Thermoreceptors = temperature differences 4. Mechanoreceptors = pressure or movement differences 5. Photoreceptors = light energy 10.2

4. Special Senses • Smell------------Olfactory Organs • Taste--------------Taste Buds • Hearing----------Ears • Equilibrium----Ears • Sight--------------Eyes 10.4

5. Olfactory Receptors = chemoreceptor s (chemicals dissolved in liquids stimulate them) • Olfactory Organs contain olfactory receptors • Olfactory Receptors Cells = neurons surrounded by cells and cilia(protrude into nasal cavity); before sense of smell, odorant molecules must dissolve in watery fluid (around cilia) • Located in upper nasal cavity 10.5 - SMELL

6. 10.5 - SMELL

7. Did you know? Humans have about 12 million olfactory receptor cells. Bloodhounds have about 4 billion such cells! • 1. Olfactory receptors stimulated (Synapse with olfactory bulb) • 2. Olfactory bulb analyze impulse • 3. Olfactory cortex (temporal lobe-brain) • 4. Sense of Smell 10.5 - SMELL

8. Taste Buds = special organs of taste • Approximately 10,000 located primarily on the surface of tongue within papillae. • Approximately 1,000 are scattered in the roof of the mouth and walls of the throat. 10.6 - TASTE

9. Each taste bud has about 50 – 150 taste cells that are replaced every 3 days. • Before a chemical can be tasted, it must be dissolved in watery fluid (saliva) surrounding the taste buds. • 4 primary taste sensations: sweet, sour, salty, bitter. 10.6 - TASTE

10. Did you know? Cats have only about 473 taste buds and dogs have about 1,700…..that is why they are satisfied with a less varied diet than humans. • Taste receptors stimulated • Impulses analyzed; sent to gustatory cortex (parietal lobe) • Sense of taste 10.6 - TASTE

11. 10.6 - TASTE

12. Ear Parts: External, Middle, Internal • Provide hearing and equilibrium 10.7 - HEARING

13. External Ear: Auricle (pinna) = funnel structure that collects sound External Acoustic Meatus (canal) = transports sound 10.7 - HEARING

14. Middle Ear: Tympanic Cavity= air filled space of temporal bone Auditory Ossicles = 3 small bones within the middle ear/tympanic cavity: malleus, incus, stapes 10.7 - HEARING

15. Auditory/Eustachian Tube = Connects the middle ear to the throat • Maintains equal air pressure on both sides of tympanic cavity 10.7 - HEARING

16. SOUND TRANSMISSION • Tympanic membrane vibrates malleus, vibrates incus, vibrates stapes • Stapes vibrates oval window fluid (inner ear) & receptors stimulated 10.7 HEARING

18. Inner Ear: Labyrinth= system of communicating chambers and tubes 2 parts to labyrinth: • Osseous Labyrinth - outside • Perilymph = fluid between Osseous & Membranous • Membranous Labyrinth - inside • Endolymph = fluid in membranous 10.7 - HEARING

20. Inner Ear: Cochlea= houses organ of hearing (organ of Corti) Organ of Corti: contains hair cells (receptors on the basilar membrane) that extend into the cochlear duct 10.7 - HEARING

22. 2 Parts: Static Equilibrium=maintain head position when still Dynamic Equilibrium = maintain balance when moving 10.8 - EQUILIBRIUM

23. STATIC: • organs of static equilibrium located in vestibule (bone chamber between semi circular canals and cochlea) • Membranous labyrinth inside vestibule has 2 chambers (utricle and saccule) • Within chambers is structure called macula that contain numerous hairs acting as sensory receptors. • Otoliths = grains of calcium carbonate w/in mass of gelatinous material 10.8 - EQUILIBRIUM

24. O

25. DYNAMIC: • organs of dynamic equilibrium are 3 semicircular canals • Semicircular canal functions = 1. detect head motion 2. balance head and body during sudden movement • Crista Ampullarisorgans of dynamic equilibrium that contain sensory hair cells • Like hairs of maculae, these extend upward into dome-shaped gelatinous mass, cupula 10.8 - EQUILIBRIUM

28. Accessory Organs • Eyelids • Lacrimal apparatus – tears lubricate & cleanse eye; contains enzyme (lysozyme) that acts as an antibacterial agent • Extrinsic muscles – six muscles attached to the sclera (white part) that move the eye in all directions 10.9 - SIGHT

30. Eye Structure (3 layers) • Outer (fibrous) layer • Middle (vascular) layer • Inner (nervous) layer • Spaces are filled with fluid that support and help maintain shape. 10.9 - SIGHT

31. Outer (fibrous) layer • Cornea transparent; helps focus entering light • Sclera white; protects the eye and point of attachment for 6 extrinsic muscles • Optic nerve and blood vessels pierce the posterior (back) 10.9 - SIGHT

32. Middle (vascular) layer • Choroid coat dark coloration; provides nourishment; keeps inside of eye dark • Ciliary body ring of ciliary muscles; holds eye in place; allows lens to change focus; • Iris colored portion; between cornea and lens; controls amount of light that enters; • Anterior Chamber = cornea & iris • Posterior Chamber = iris & lens • Aqueous Humor = fluid that fills space and helps nourish 10.9 - SIGHT

33. Inner (nervous) layer • Retina contain visual receptor cells (photoreceptors) • When a person sees something, the object is giving off light or light waves are reflected from it. Light waves enter eye and retina focuses it by bending the light waves (refraction). 10.9 - SIGHT

34. Inner (nervous) layer • 2 types of visual receptors: Rods & Cones • Rods = light sensitivity • Cones = color 10.9 - SIGHT