1. 1 Senses General Senses receptors that are widely distributed throughout the body skin, various organs and joints Special Senses specialized receptors confied to structures in the head eyes and ears

2. 2 Senses Sensory Receptors specialized cells or multicellular structures that collect information from the environment stimulate neurons to send impulses along sensory fibers to the brain Sensation a feeling that occurs when brain becomes aware of sensory impulse Perception a person’s view of the stimulus; the way the brain interprets the information

3. 3 Receptor Types Chemoreceptors respond to changes in chemical concentrations Pain receptors (Nociceptors) respond to tissue damage Thermoreceptors respond to changes in temperature Mechanoreceptors respond to mechanical forces Photoreceptors respond to light

4. 4 General Senses senses associated with skin, muscles, joints, and viscera three groups exteroceptive senses – senses associated with body surface; touch, pressure, temperature, pain visceroceptive senses – senses associated with changes in viscera; blood pressure stretching blood vessels, ingesting a meal proprioceptive senses – senses associated with changes in muscles and tendons

5. 5 Touch and Pressure Senses Free nerve endings common in epithelial tissues simplest receptors sense itching Meissner’s corpuscles abundant in hairless portions of skin; lips detect fine touch; distinguish between two points on the skin Pacinian corpuscles common in deeper subcutaneous tissues, tendons, and ligaments detect heavy pressure and vibrations

6. 6 Touch and Pressure Receptors

7. 7 Sense of Pain free nerve endings widely distributed nervous tissue of brain lacks pain receptors stimulated by tissue damage, chemical, mechanical forces, or extremes in temperature adapt very little, if at all

8. 8 Visceral Pain pain receptors are the only receptors in viscera whose stimulation produces sensations pain receptors respond differently to stimulation not well localized may feel as if coming from some other part of the body - known as referred pain

9. 9 Referred Pain may occur due to sensory impulses from two regions following a common nerve pathway to brain

10. 10 Temperature Senses Warm receptors sensitive to temperatures above 25 o C (77 o F) unresponsive to temperature above 45 o C(113 o F) Cold receptors sensitive to temperature between 10 o C (50 o F) and 20 o C (68 o F) Pain receptors respond to temperatures below 10 o C respond to temperatures above 45 o C

11. 11 Special Senses sensory receptors are within large, complex sensory organs in the head smell in olfactory organs taste in taste buds hearing and equilibrium in ears sight in eyes

12. 12 Sense of Smell Olfactory Receptors chemoreceptors respond to chemicals dissolved in liquids Olfactory Organs contain olfactory receptors and supporting epithelial cells cover parts of nasal cavity, superior nasal conchae, and a portion of the nasal septum

13. 13 Olfactory Receptors

14. 14 Olfactory Nerve Pathways Once olfactory receptors are stimulated, nerve impulses travel through olfactory nerves olfactory bulbs olfactory tracts limbic system (for emotions) and olfactory cortex (for interpretation)

15. 15 Sense of Taste Taste Buds organs of taste located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx Taste Receptors chemoreceptors taste cells – modified epithelial cells that function as receptors taste hairs –microvilli that protrude from taste cells; sensitive parts of taste cells

16. 16 Taste Receptors

17. 17 Taste Sensations Four Primary Taste Sensations sweet – stimulated by carbohydrates sour – stimulated by acids salty – stimulated by salts bitter – stimulated by many organic compounds Spicy foods activate pain receptors

18. 18 Taste Nerve Pathways Sensory impulses from taste receptors travel along cranial nerves to medulla oblongata to thalamus to gustatory cortex (for interpretation)

19. 19 Hearing Ear – organ of hearing Three Sections External Middle Inner

20. 20 External Ear auricle collects sounds waves external auditory meatus lined with ceruminous glands carries sound to tympanic membrane terminates with tympanic membrane tympanic membrane vibrates in response to sound waves

21. 21 Middle Ear tympanic cavity air-filled space in temporal bone auditory ossicles vibrate in response to tympanic membrane malleus, incus, and stapes oval window opening in wall of tympanic cavity stapes vibrates against it to move fluids in inner ear

22. 22 Auditory Tube eustachian tube connects middle ear to throat helps maintain equal pressure on both sides of tympanic membrane usually closed by valve-like flaps in throat

23. 23 Inner Ear complex system of labyrinths osseous labyrinth bony canal in temporal bone filled with perilymph membranous labyrinth tube within osseous labyrinth filled with endolymph

24. 24 Inner Ear Three Parts of Labyrinths cochlea functions in hearing semicircular canals functions in equilibrium vestibule functions in equilibrium

25. 25 Auditory Nerve Pathways

26. 26 Equilibrium Static Equilibrium vestibule sense position of head when body is not moving Dynamic Equilibrium semicircular canals sense rotation and movement of head and body

27. 27 Sight Visual Accessory Organs eyelids lacrimal apparatus extrinsic eye muscles

28. 28 Eyelid palpebra composed of four layers skin muscle connective tissue conjunctiva orbicularis oculi - closes levator palperbrae superioris – opens tarsal glands – secrete oil onto eyelashes conjunctiva – mucous membrane; lines eyelid and covers portion of eyeball

29. 29 Lacrimal Apparatus lacrimal gland lateral to eye secretes tears canaliculi collect tears lacrimal sac collects from canaliculi nasolacrimal duct collects from lacrimal sac empties tears into nasal cavity

30. 30 Structure of the Eye hollow spherical wall has 3 layers outer fibrous tunic middle vascular tunic inner nervous tunic

31. 31 Outer Tunic Cornea anterior portion transparent light transmission light refraction Sclera posterior portion opaque protection

32. 32 Middle Tunic Iris anterior portion pigmented controls light intensity Ciliary body anterior portion pigmented holds lens moves lens for focusing Choroid coat provides blood supply pigments absorb extra light

33. 33 Anterior Portion of Eye filled with aqueous humor

34. 34 Lens transparent biconvex lies behind iris largely composed of lens fibers elastic held in place by suspensory ligaments of ciliary body

35. 35 Ciliary Body forms internal ring around front of eye ciliary processes – radiating folds ciliary muscles – contract and relax to move lens

36. 36 Accommodation changing of lens shape to view objects

37. 37 Iris composed of connective tissue and smooth muscle pupil is hole in iris dim light stimulates radial muscles and pupil dilates bright light stimulates circular muscles and pupil constricts

38. 38 Aqueous Humor fluid in anterior cavity of eye secreted by epithelium on inner surface of the ciliary body provides nutrients maintains shape of anterior portion of eye leaves cavity through canal of Schlemm

39. 39 Inner Tunic retina contains visual receptors continuous with optic nerve ends just behind margin of the ciliary body composed of several layers macula lutea – yellowish spot in retina fovea centralis – center of macula lutea; produces sharpest vision optic disc – blind spot; contains no visual receptors vitreous humor – thick gel that holds retina flat against choroid coat

40. 40 Posterior Cavity contains vitreous humor – thick gel that holds retina flat against choroid coat

41. 41 Focusing On Retina as light enters eye, it is refracted by convex surface of cornea convex surface of lens image focused on retina is upside down and reversed from left to right

42. 42 Visual Receptors Rods long, thin projections contain light sensitive pigment called rhodopsin hundred times more sensitive to light than cones provide vision in dim light produce colorless vision produce outlines of objects Cones short, blunt projections contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe provide vision in bright light produce sharp images produce color vision

43. 43 Rods and Cones

44. 44 Visual Pigments Rhodopsin light-sensitive pigment in rods decomposes in presence of light triggers a complex series of reactions that initiate nerve impulses impulses travel along optic nerve Pigments on Cones each set contains different light-sensitive pigment each set is sensitive to different wavelengths color perceived depends on which sets of cones are stimulated erythrolabe – responds to red chlorolabe – responds to green cyanolabe – responds to blue

45. 45 Rod Cells

46. 46 Stereoscopic Vision provides perception of distance and depth results from formation of two slightly different retinal images

47. 47 Life-Span Changes Age related hearing loss due to damage of hair cells in organ of Corti degeneration of nerve pathways to the brain tinnitus Age-related visual problems include dry eyes floaters (crystals in vitreous humor) loss of elasticity of lens glaucoma cataracts macular degeneration

48. 48 Visual Nerve Pathway

49. 49 Clinical Application Refraction Disorders concave lens corrects nearsightedness convex lens corrects farsightedness