1. Senses
A&P Spring 2016

2. Think about it
If you had to lose one of your senses, which one would you prefer to lose?
Why?
How could you compensate for loosing that sense?
Which one would you hate to lose the most?

3. Sense of Hearing and Equilibrium
The Ear
The organ of hearing and equilibrium
Has outer, middle and inner parts

4. Sense of Hearing and Equilibrium
Outer ear- consists of 3 parts
Auricle- funnel-like structure
External acoustic meatus- S-shaped tube
Eardrum- semitransparent membrane

6. Sense of Hearing and Equilibrium
The eardrum
Covered by a thin layer of skin on the outside and mucous membrane on the inside
Has an oval margin and is cone-shaped
Apex of cone directed inward
Sounds waves change the pressure on the eardrum
The eardrum moves back and forth in response
Reproduces the vibrations of the sound wave source

8. Sense of Hearing and Equilibrium
The Middle Ear
A.k.a. tympanic cavity
Air-filled space in the temporal bone
Contains auditory ossicles (3 small bones)
Auditory tube connects here

9. Sense of Hearing and Equilibrium
Auditory Ossicles
Malleus
Incus
Stapes
Bridge the eardrum and inner ear
Transmit and amplify vibrations between these parts

11. Sense of Hearing and Equilibrium
Auditory Tube
Connects each middle ear to the throat
Helps maintain equal air pressure on both sides of the eardrum

12. Sense of Hearing and Equilibrium
Inner Ear
Labyrnth

13. Sense of Hearing and Equilibrium
Labyrinth
Complex system of communicating chambers and tubes
Two parts
Osseous labyrinth- bony outside
Membranous labyrinth- soft inside

15. Sense of Hearing and Equilibrium
The labyrinth contains 3 semicircular canals and a cochlea
Semicircular canals provide a sense of equilibrium
Cochlea functions in hearing

16. Sense of Hearing and Equilibrium
Cochlea
Cochlear duct- name for membranous labyrinth inside the cochlea
Surrounded by vestibular and basilar membranes
Organ of Corti
Contains hearing receptors
Located on the surface of the basilar membrane
Two frequencies of sound waves stimulate different sets of these receptors

18. Sense of Hearing and Equilibrium
The ear of a young person can normally detect sound waves with frequencies between 20 and 20,000 vibrations per second
The range of greatest sensitivity is 2,000-3,000 vibrations per second
How good is your hearing?
Hearing Test

19. Sense of Hearing and Equilibrium
Equilibrium- actually two senses
Static equilibrium
Dynamic equilibrium

20. Sense of Hearing and Equilibrium
Static equilibrium
Senses position of head
Maintains stability and posture when head and body are still
Dynamic equilibrium
Detects motion of head and body
Maintains balance while moving

22. Sense of Sight
The Eye
Organ that contains visual receptors and provides vision
Has outer, middle and inner layers

23. Sense of Sight
Outer Layer- 3 major parts
Cornea
Sclera
Optic nerve

24. Sense of Sight Cornea- “window of the eye”
Helps focus entering light rays

25. Sense of Sight Sclera- white portion of the eye
Continuous with the cornea
Protects the eye
Attachment for extrinsic muscles

26. Sense of Sight Optic Nerve Pierces the sclera in the back of the eye
Innervates the eye itself

27. Sense of Sight
Middle Layer- 3 parts
Choroid coat
Ciliary body
Iris

28. Sense of Sight Choroid coat
Contains blood vessels which nourish surrounding tissues
Contains melanin producing cells
Melanin absorbs excess light
Helps keep the inside of the eye dark

30. Sense of Sight Ciliary Body
Forms internal ring around the front of the eye
Helps hold the lens in position
Also allow lens to adjust shape to facilitate focusing

31. Sense of Sight Iris Lies between the cornea and lens
Forms the colored portion of the eye that we see
Opening in the middle is the pupil

32. Sense of Sight Inner Layer- 1 part Retina
Contains visual receptor cells
Has 3 main regions
Macula Lutea
Fovea centralis
Optic disc

34. Sense of Sight Regions of the Retina Macula Lutea
Central region that appears as a yellowish spot

35. Sense of Sight Fovea Centralis
Depression in the center of the macula lutea
Produces the sharpest vision

36. Sense of Sight Optic disc Outside the macula lutea
Nerve fibers leave the eye and join the optic nerve
Contains central blood artery and vein
Lacks receptor cells- “blind spot”

37. Sense of Sight Visual Receptors Rods Black and white vision
General outlines of objects
Cones
Color vision
Sharp images

38. Sense of Smell Olfactory Organs Located within the nasal cavity
Small masses of epithelium

39. Sense of Smell Olfactory Receptor Cells
Neurons surrounded by epithelial cells
Chemoreceptors- chemicals dissolved in liquids stimulate them

40. Sense of Smell So many smells, not so many receptors
One odorant molecule may bind to many different receptors
One receptor may be able to bind many different odorant molecules

41. Sense of Smell
Brain interprets this binding info as a combinational code
Kind of like a combination lock
Chocolate may stimulate receptors 1, 5 and 10 while parsley stimulates 3, 4 and 8

42. Sense of Taste Organs of taste Taste buds About 10,000 of them
Located mostly on the tongue

43. Sense of Taste Taste receptor cells
Each taste bud has receptor cells
Each cell is replaced every three days
Chemoreceptors

44. Sense of Taste Taste Sensations Sweet- table sugar Sour- lemon
Salty- table salt
Bitter- caffeine

45. Sense of Taste Taste Sensitivities Tip of tongue- sweet
Sides of tongue- sour
Back of the tongue- bitter
Anywhere- salty
This happens because certain receptors respond more to certain tastes

46. Sense of Touch Derives from three kinds of receptors
Free Nerve Endings
Meissner’s Corpuscles
Pacinian Corpuscles
Sense mechanical forces that deform or displace tissues

47. Sense of Touch Free Nerve Endings Common in epithelial tissues
Free ends extend between epithelial cells
Can sense both touch and pressure

48. Sense of Touch Meissner’s Corpuscles
Small, oval masses of flattened connective tissue cells
Two or more sensory nerve fibers branch into each one
Abundant in the hairless portions of skin
Lips, fingertips, palms, etc
Respond to motion of objects barely contacting the skin
Give the sensation of light touch

50. Sense of Touch Pacinian Corpuscles
Relatively large structures composed of connective tissue
Common in deeper subcutaneous tissues, tendons and ligaments
Respond to heavy pressure
Gives the sensation of deep pressure

52. Sense of Touch Temperature Senses Two types of free nerve endings
Warm receptors
Cold receptors
Adapt rapidly
After about a minute of continuous stimulation, sensation begins to fade

53. Sense of Touch Warm Receptors
Most sensitive to temperatures above 25 degrees C
Become unresponsive at temperatures above 45 degrees C
Temperatures near and above 45 degrees C stimulate pain receptors
Produces a burning sensation

54. Sense of Touch Cold Receptors
Most sensitive to temperatures between degrees C
Temperatures below 10 degrees C stimulate pain receptors
Produces a freezing sensation

55. Sense of Touch Sense of Pain Free nerve endings
Distributed throughout the body, except the brain
Protect the body
Tissue damage stimulates them

56. Sense of Touch Visceral (Organ) Pain
Receptors in the organs respond differently than other receptors
Ex. May not feel pain after surgery but will feel pain after a spasm of the muscles in the intestinal walls

58. Sense of Touch Referred Pain
Visceral pain that feels like it’s coming from another part of the body
May stem from nerve pathways that carry sensory impulses from both skin and visceral receptors
Might be why the left shoulder and arm begins to hurt during a heart attack

59. The End!
Hooray!
Brain Games!