1. Misericordia University
Sensory
General Physiology
Tony Serino, Ph.D.
Biology Department
Misericordia University

2. 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. Receptor Physiology
Stimulation of a receptor leads to the generation of a receptor (generator) potential in its membrane.
These are usually excitatory, and are similar to the EPSPs found in neurons
If the receptor potential reaches the threshold potential for the sensory neuron; it fires an AP into the CNS
Strength of the stimulus is therefore encoded by the number of AP generated
Sensations may be sharpened through Lateral Inhibition

9. Lateral Inhibition - -

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

11. Sensitivity of Skin due to Receptive Fields

12. Proprioceptors

13. 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

14. Relationship of Stretch to AP

15. Referred Pain
Illustrates projection.

16. General Pathway of Perception

17. Taste (Gustatory) Sense

19. Olfaction (smell) Sense

20. Olfactory Epithelium

21. Olfaction Signal Transduction

22. Vision

23. Eye Anatomy

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

25. Iris controls amount of light entering the eye.

26. Distant Vision

27. Near Vision (Accomodation)

28. Near and Far-sightedness

29. 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.

30. Retina Cellular Arrangement

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

32. Photoreceptors: Cones and Rods

33. Three Population of Cones

34. Rod’s and Cone’s Photopigments

35. Rhodopsin

37. Light Signal Transduction

38. Visual Processing

39. Sound

40. Frequency vs. Loudness Frequency measured in hertz (Hz)
Loudness measured in decibels (dB)

41. Anatomy of the Ear

42. Ossicles Amplify Sound

43. Cochlea and Cochlear Duct

44. Frequency Perception
Different frequency (pitch) of sound stimulates different areas of cochlear duct
The overall area stimulated relates to the sound intensity

45. Vestibular Apparatus

46. Macula of Utricle and Saccule

47. Macula
Otoconia (otoliths)

48. Hair Cell of Macula

49. AP Generation in Macula

50. Ampulla Anatomy