1. Sensory Systems
Vision
Hearing
Taste
Smell
Equilibrium
Somatic Senses

2. Sensory Systems Somatic sensory Visceral sensory
General – transmit impulses from skin, skeletal muscles, and joints
Special senses - hearing, balance, vision
Visceral sensory
Transmit impulses from visceral organs
Special senses - olfaction (smell), gustation (taste)

3. Properties of Sensory Systems
Stimulus - energy source
Internal
External
Receptors
Sense organs - structures specialized to respond to stimuli
Transducers - stimulus energy converted into action potentials
Conduction
Afferent pathway
Nerve impulses to the CNS
Translation
CNS integration and information processing
Sensation and perception – your reality

4. Sensory Pathways
Stimulus as physical energy  sensory receptor acts as a transducer
Stimulus > threshold  action potential to CNS
Integration in CNS  cerebral cortex or acted on subconsciously

5. Classification by Function (Stimuli)
Mechanoreceptors – respond to touch, pressure, vibration, stretch, and itch
Thermoreceptors – sensitive to changes in temperature
Photoreceptors – respond to light energy (e.g., retina)
Chemoreceptors – respond to chemicals (e.g., smell, taste, changes in blood chemistry)
Nociceptors – sensitive to pain-causing stimuli
Osmoreceptors – detect changes in concentration of solutes, osmotic activity
Baroreceptors – detect changes in fluid pressure

6. Classification by Location
Exteroceptors – sensitive to stimuli arising from outside the body
Located at or near body surfaces
Include receptors for touch, pressure, pain, and temperature
Interoceptors – (visceroceptors) receive stimuli from internal viscera
Monitor a variety of stimuli
Proprioceptors – monitor degree of stretch
Located in musculoskeletal organs

7. Classification by Structure

8. Somatic Senses
General somatic – include touch, pain, vibration, pressure, temperature
Proprioceptive – detect stretch in tendons and muscle provide information on body position, orientation and movement of body in space

9. Somatic Receptors Divided into two groups
Free or Unencapsulated nerve endings
Encapsulated nerve endings - consist of one or more neural end fibers enclosed in connective tissue

10. Free Nerve Endings
Abundant in epithelia and underlying connective tissue
Nociceptors - respond to pain
Thermoreceptors - respond to temperature
Two specialized types of free nerve endings
Merkel discs – lie in the epidermis, slowly adapting receptors for light touch
Hair follicle receptors – Rapidly adapting receptors that wrap around hair follicles

11. Encapsulated Nerve Endings
Meissner’s corpuscles
Spiraling nerve ending surrounded by Schwann cells
Occur in the dermal papillae of hairless areas of the skin
Rapidly adapting receptors for discriminative touch
Pacinian corpuscles
Single nerve ending surrounded by layers of flattened Schwann cells
Occur in the hypodermis
Sensitive to deep pressure – rapidly adapting receptors
Ruffini’s corpuscles
Located in the dermis and respond to pressure
Monitor continuous pressure on the skin – adapt slowly

12. Encapsulated Nerve Endings - Proprioceptors
Monitor stretch in locomotory organs
Three types of proprioceptors
Muscle spindles – monitors the changing length of a muscle, imbedded in the perimysium between muscle fascicles
Golgi tendon organs – located near the muscle-tendon junction, monitor tension within tendons
Joint kinesthetic receptors - sensory nerve endings within the joint capsules, sense pressure and position

13. Muscle Spindle & Golgi Tendon Organ

14. Special Senses Smell Taste Vision Hearing Equilibrium
Figure 10-4: Sensory pathways

15. Vision

16. External Structures of the Eye
Figure 17.3a, b

17. Internal Structures of the Eye

18. Eye anatomy
Ciliary body and lens divide the eye into posterior (vitreous) cavity and anterior cavity
Anterior cavity further divided into anterior and posterior chambers
Aqueous humor circulates within the eye
diffuses through the walls of anterior chamber
re-enters circulation
Vitreous humor fills the posterior cavity.
Not recycled – permanent fluid

19. The Pupillary Muscles
Figure 17.5

20. Sectional Anatomy of the Eye
Outer fibrous tunic -sclera, cornea,
Vascular tunic - iris, ciliary body, choroid
Nervous tunic - retina
Figure 17.4a, b

21. Organization of the Retina
Figure 17.6b, c

22. Organization of the Retina
Figure 17.6a

23. Retina
Figure 10-38: Photoreceptors: rods and cones

24. Retina Rod cells Cone cells: Pigmented epithelium
Monochromatic
Night vision
Cone cells:
Red, green, & blue
Color & details
Pigmented epithelium
Melanin granules
Prevents reflection
Bipolar & ganglion cells converge, integrate APs

25. Vision: Photoreceptors
Reflected light translated into mental image
Pupil limits light, lens focuses light
Retinal rods and cones are photoreceptors
Figure 10-36: Photoreceptors in the fovea

26. Lens – Image Formation Lens helps focus
Light is refracted as it passes through lens
Accommodation is the process by which the lens adjusts to focus images
Normal visual acuity is 20/20

27. Accommodation
Figure 17.10

28. Visual Abnormalities
Figure 17.11

29. Photoreception and Local Integration
Figure 10-35: ANATOMY SUMMARY: The Retina

30. Visual physiology

31. Photoreception Retinal Changes Shape Retinal restored
Opsin inactivated
Figure 17.15

32. Convergence and Ganglion Cell Function
Figure 17.18

33. Visual Pathways
Figure 17.19

34. Equilibrium and Hearing
Both Equilibrium And Hearing Are Provided By Receptors Of The Inner Ear

35. Anatomy of the ear

36. Middle Ear
Figure 17.21

37. Inner ear Membranous labyrinth contains endolymph
Bony labyrinth surrounds and protects membranous labyrinth
Vestibule
Semicircular canals
Cochlea

38. Cochlea
Figure 17.25a, b

39. Sound and Hearing
Sound waves travel toward tympanic membrane, which vibrates
Auditory ossicles conduct the vibration into the inner ear
Movement at the oval window applies pressure to the perilymph of the cochlear duct
Pressure waves distort basilar membrane
Hair cells of the Organ of Corti are pushed against the tectoral membrane
Figure 17.28a

40. The Organ Of Corti
Figure 17.26a, b

41. Equilibrium

42. Semicircular Canals Provide information about rotational acceleration.
Project in 3 different planes.
Each canal contains a semicircular duct.
At the base is the crista ampullaris, where sensory hair cells are located.
Hair cell processes are embedded in the cupula.
Endolymph provides inertia so that the sensory processes will bend in direction opposite to the angular acceleration.

44. Structure of the Macula

45. Utricle and Saccule Utricle: Saccule:
More sensitive to horizontal acceleration.
During forward acceleration, otolithic membrane lags behind hair cells, so hairs pushed backward.
Saccule:
More sensitive to vertical acceleration.
Hairs pushed upward when person descends.

46. Smell (Olfacation) & Taste (Gustation)

47. Olfactory organs
Contain olfactory epithelium with olfactory receptors, supporting cells, basal cells
Olfactory receptors are modified neurons
Surfaces are coated with secretions from olfactory glands
Olfactory reception involved detecting dissolved chemicals as they interact with odorant binding proteins

48. Olfaction Olfactory pathways Olfactory discrimination
No synapse in the thalamus for arriving information
Olfactory discrimination
Can distinguish thousands of chemical stimuli
CNS interprets smells by pattern of receptor activity
Olfactory receptor population shows considerable turnover
Number of receptors declines with age

49. Taste Receptors Clustered in taste buds
Associated with lingual papillae
Taste buds
Contain basal cells which appear to be stem cells
Gustatory cells extend taste hairs through a narrow taste pore

50. Gustatory pathways Taste buds are monitored by cranial nerves
Synapse within the solitary nucleus of the medulla oblongata
Then on to the thalamus and the primary sensory cortex
Primary taste sensations
Sweet, sour, salty, bitter
Receptors also exist for umami and water
Taste sensitivity shows significant individual differences, some of which are inherited
The number of taste buds declines with age