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Special Senses special location. Smell (olfaction)taste (gustation)Vision (optic)Balance (equilibrium)Hearing (auditory). General Senses Somatic
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1. Somatic Senses & Special Senses Chapter 12
2. Special Sensesspecial location Smell (olfaction)
taste (gustation)
Vision (optic)
Balance (equilibrium)
Hearing (auditory)
3. General SensesSomatic & Visceral Somatic senses:
Temperature
Touch
Pressure
Vibration
Proprioception
Pain
Visceral senses: Internal organ conditions
4. Definition of Sensation Conscious or subconscious awareness of change in external or internal environment
Requires:
Stimulus
Sensory receptor
Neural pathway
Brain region for integration
5. Characteristics Perception- conscious awareness
Cerebral cortex function
Adaptation- decreased receptor response with prolonged stimulation
decreased perception
Adaptation speed varies with receptor
6. Structural Types Free nerve endings-
pain, thermal, tickle, itch & some touch receptors
Encapsulated nerve endings
Touch pressure & vibration
Specialized cells:
e.g. hair cells in inner ear
7. Receptor Mechanisms Mechanoreceptors-
cell deformation, stretching or bending
Thermoreceptors- temperature
Nociceptors � pain
Photoreceptors- light
Chemoreceptors- chemicals
Taste, smell, body fluid content
8. Somatic Senses Receptors- distributed unevenly
In skin, mucous membranes, muscles, tendons,& joints
Dense receptors concentration in fingertips, lips & tip of tongue
9. Tactile sensations Touch, pressure, vibration, itch & tickle
Itch & tickle � free nerve endings
encapsulated mechanoreceptors
10. Touch ? Rapidly adapting receptors:
Meisner corpuscles
Hair root plexuses
Slowly adapting receptors:
Type I mechanoreceptors= Merkel discs-
surface receptors- stratum basale
Type II mechanoreceptors= Ruffini corpuscles- deep in dermis & tendons
11. Pressure & Vibration Sensation over large area
Lamellated or Pacinian corpuscles
Rapid adapting & widely distributed
Vibration = rapidly repetitive stimuli
Corpuscles of touch- low frequency
Lamellated corpuscles- higher frequency
12. Figure 12.1
13. Itch & tickle Itch- chemical stimulation of free nerve endings
Bradykinin from inflammation response
Tickle- from free nerve endings & lamellated corpuscles
Requires someone else- blocked by signals from cerebellum
14. Thermal Sensations Two kinds of thermoreceptors-
Between 10o & 40o C - cold
Located in epidermis
Between 32o & 48o C � warm
located in dermis
Outside these ranges � nociceptors
Both adapt rapidly but continue slow signals during prolonged stimulus
15. Pain Sensations Nociceptors- free nerve endings
Found in every tissue but brain
Very little adaptation
Fast pain= acute, sharp pain (0.1 sec)
not felt in deep tissues and well localized
Slow pain- slow starting & increases
Chronic, burning, aching or throbbing sensation
Visceral pain location displaced to surface = referred pain
16. Figure 12.2
17. Proprioception Head and limb position & motion
Located in muscles (muscle spindles), tendons (tendon organs), in & around synovial joints (joint kinesthetic receptors)
Kinesthesia= perception of movements
Inner ear (hair ceils)- head position
Tracts to primary sensory area of cerebral cortex & cerebellum
Slow & slight adaptation
18. Figure 10.13
19. Smell- Olfaction In upper surface of superior concha, below cribiform plate
Olfactory receptors-
first order neurons of olfactory pathway
Connect to olfactory bulb
Have olfactory hairs containing chemoreceptors
Supporting cells-
epithelial cells � support & electrical insulation
Basal cells- stem cells for receptors
20. Figure 12.3a
21. Stimulation of Receptors Genetic evidence- 100�s of primary odors
Binding of chemical stimulates nerve
Recognition of 10,000 odors from combination of primary receptor input
Rapid adaptation by ~50% in 1 sec.
22. Figure 12.3 b
23. Taste- Gustatory Sensation 5 primary tastes: salt, sweet, sour, bitter & umami
Perception of what we call taste includes olfactory input
Receptors in taste buds (~10,000)
Located on tongue & pharynx & epiglottis
In structures called papillae
Vallate (back), fungiform (all over)
filiform- touch receptors only
24. Figure 12.4a
25. Figure 12.4b
26. Structure of Taste Bud Epithelial cells:
Supporting cells surrounding
Gustatory receptor cells
Gustatory hair projects from receptor through taste pore
Basal cells= stem cells
Produce supporting cells that develop into receptor cells (10 day life span)
27. Figure 12.4c
28. Vision- Eyes Accessory structures-
eye brows, eyelashes- protection
eye lids- protection & lubrication (blinking)
extrinsic muscles- moving eyeball
Superior Rectus, inferior rectus, lateral rectus, medial rectus, superior oblique, inferior oblique
Lacrimal apparatus-
Gland? lacrimal duct? surface of upper eyelid ? lacrimal canal & nasolacrimal duct ? nasal cavity
29. Figure 12.5
30. Layers of Eyeball Fibrous tunic � Anterior clear cornea
Sclera- white of eye
Vascular tunic- contains:
Choroid- Lines most of internal surface
carries blood vessels
Ciliary body- focuses the lens and secretes aqueous humor
Iris- opens & closes pupil-
contains pigment of eye color.
Pupil = hole for light passage
Adjusted by iris to control amount of light through the lens
31. Figure 12.6
32. Figure 12.7
33. Photoreceptors Rods very sensitive, black & white
Cones- color sensitive,
3 types-blue, green & red
Color vision results from combined input
Cones mostly in central fovea
6 million cones
120 million rods
34. Figure 12.8
35. Interior of Eyeball Two cavities- divided by lens
Anterior cavity: filled with aqueous humor
Vitreous chamber: filled with vitreous body
Gel-like - holds retina against choroid
36. What you see
Lens- focuses light on the retina
Image is inverted but brain adjusts & interprets distance and size
37. Figure 12.12
38. Structures of ear Outer ear- Auricle, external auditory canal & tympanic membrane (ear drum)
Canal contains hairs & ceruminous glands
Middle ear- auditory tube (eustachian tube) & ossicles
Ossicles = Malleus, incus, & stapes-attached to oval window
Inner ear- Bony labyrinth & membranous labyrinth filled with endolymph
Cochlea- sense organ of hearing ,
vestibule & semicircular canals- organs of balance
39. Spiral Organ Contains supporting cells & hair cells
Hair cells =receptors for auditory sensations
40. Figure 12.13a
41. Figure 12.13b
42. Figure 12.14
43. Physiology of Equilibrium Static equilibrium- position relative to gravity
Dynamic equilibrium- position in response to head movement
44. Static equilibrium gravity pulls on otoliths in otolithic membrane
bends hair cells
45. Figure 12.15a
46. Figure 12.15b
47. Dynamic Equilibrium Semicircular canals- at right angles to each other
Cristae in each ampulla have hair cells and supporting cells
When head turns hair cells move
Endolymph lags and bends hair cells
Bend triggers nerve impulse in vestibular branch
48. Figure 12.16a
49. Figure 12.16b