1. General Sensation and Vision
Orbital Region
General Sensation and Vision

2. Generalized Sensation Physiology
Sensation –state of awareness of external and internal conditions of the body
Four conditions for sensation:
1. Adequate stimulus
2. Adequate receptor (transducer)
3. Conduction
4. Translation (interpretation)

3. Brain’s Assumption in Translating
Assumption: Source of light is from above

4. Reversing X pattern; notice shading.

5. How many triangles?
Assumption: Straight lines should connect.

6. Which dark line is larger?
Assumption: perspective

7. Characteristics of Sensation
Modality –ability to interpret nerve impulses differently
Projection –referral of sensation to point of origin
Adaptation –decrease in sensitivity of receptors to continued stimulation
Phasic (fast)
Tonic (slow)
Some receptors never adapt (pain, cold, etc.)
Afterimage –persistence of sensation after stimulus ceases

8. Classification of Receptors
Type of Sensory Information Relayed
Exteroreceptors, Enteroreceptors, Proprioceptors
Type of Stimulus Transduced
Mechanoreceptors, Thermoreceptors, Chemoreceptors, and Nociceptors
Complexity of Receptor
Simple structure (usually single cell) –most general senses
Complex structure (many cells) –special senses

9. General Senses Cutaneous –skin receptors
Proprioception –sense of body position
Nociception –pain perception (chemoreceptors that perceive locally secreted warning hormones (prostaglandins))

10. Distribution of Cutaneous Receptors

11. Sensitivity of Skin due to Receptive Fields

12. Cutaneous Receptors

14. Proprioceptors

15. Muscle sensors Muscle spindles (Intrafusal fibers:
-senses degree of length of muscle fibers and the rate of change in length
Golgi Tendon organs –sense tension within tendon

16. Relationship of Stretch to AP

17. Referred Pain
Illustrates projection.

18. General Pathway of Perception

19. Orbital Region

20. Accessory Structures of the Eye

21. Eyelid

22. Lacrimal Apparatus

23. Outer Eye

24. Extrinsic Ocular Muscles

25. Arrangement of Posterior Orbit
Trochlear
Optic Nerve
Occulomotor
Abducens

26. Action and Innervation of Ocular Muscles

27. Action and Innervation of Ocular Muscles
Which cranial nerve is injured?

28. Orbital Blood Supply Ophthalmic Middle Meningeal to Cavernous sinus
Internal Carotid
Facial v.

29. Eye Anatomy

30. Aqueous Humor Flow
(Canal of Schlemm)
Glaucoma results from inadequate drainage of Aqueous Humor leading to increase pressure in the eye.

31. Iris controls amount of light entering the eye.

32. Distant Vision

33. Near Vision (Accomodation)

34. Near and Far-sightedness

35. Astigmatism and Presbyopia
Astigmatism –results from imperfections in the resolving structures in the eye (lens and/or cornea)
Presbyopia is the loss of near vision with age; resulting from a decrease in elasticity of the lens.

36. Increase lens opacity with age.
Cataract

37. Retina Cellular Arrangement

38. Special Areas of Retina

39. Blind Spot
Optic Disc (blind spot)
Optic N.

40. Photoreceptors: Cones and Rods
Three populations of cones

41. Rod’s and Cone’s Photopigments

42. Retinal Bleaching

43. Visual Processing