Biology 211 Anatomy & Physiology I

1. Biology 211Anatomy & Physiology I Special Senses

2. Special Senses 1. All confined to head 2. All special senses reach the central nervous system through cranial nerves 3. Consist of highly specialized cells which serve as receptors 4. These specialized receptor cells housed in sensory organs which are also specialized for a particular function.

3. Special Senses Specialized Receptor Cells Specialized Organ..... TASTE: SMELL: VISION: HEARING: EQUILIBRIUM: Gustatory Cells Taste Buds Olfactory Cells Olfactory Epithelium Rods & Cones Eye (Retina) Hair Cells Cochlea Hair Cells Vestibular Apparatus

4. Start with Vision: Specialized Receptor Cells Specialized Organ..... VISION: Other structures of eye regulate amount of light reaching retina and focus it on rod and cone cells.

7. The eyeball has three layers or "tunics: Strong connective tissue Protects the eye Holds shape of eye Insertion of extraoccular muscles Contains blood vessels Pigmented Contains smooth muscle cells Contains rod and cone cells and Other neurons to transmit visual information to brain

8. Layers ("tunics") of the eyeball Fibrous Layer Vascular Layer Sensory Layer

11. Focus: Majority of light refraction (bending) occurs in cornea. Not adjustable "Fine tuning" of light refraction occurs in lens: Thicker = more refraction Thinner = less refraction

15. Rods: Cones:

18. Special Senses Specialized Receptor Cells Specialized Organ..... TASTE: SMELL: VISION: HEARING: EQUILIBRIUM: Gustatory Cells Taste Buds Olfactory Cells Olfactory Epithelium Rods & Cones Eye (Retina) Hair Cells Cochlea Hair Cells Vestibular Apparatus

19. Next: Hearing Specialized Receptor Cells Specialized Organ..... HEARING Located in inner ear. Outer ear and middle ear serve to transmit and regulate the volume of sound

21. The inner ear contains a complex fluid-filled structure, the membranous labyrinth, which is embedded in the temporal bone. Outer ear channels air vibrations (sound) to the tympanic membrane (eardrum) The middle ear is an air-filled chamber containing three ossicles: the malleus, the incus, & the stapes

22. Malleus Incus Stapes (attaches to oval window of inner ear) Tympanic membrane

23. The tympanic membrane is attached to the malleus, which is attached to the incus, which is attached to the stapes, which is attached to the oval window of the membranous labyrinth of the inner ear. The membranous labyrinth is fluid-filled. Therefore: Vibrations of air (sound) vibrate the tympanic membrane Which makes the ossicles vibrate Which makes the oval window vibrate Which makes the fluid of the membranous labyrinth of the inner ear vibrate This is how the vibrations get transmitted from the air of the outer ear to the receptor cells of the cochlea in the inner ear

24. The membranous labyrinth of the inner ear actually consists of two sets of tubes, one inside the other. The outer tube is filled with a fluid called , while the inner tube is filled with fluid called

25. At one end of inner ear, these two tubes (one inside the other) coil about 2 & 2/3 times to form the Vibrations of the oval window actually make the perilymph vibrate. This must be transmitted to the endolymph within the cochlea before the hair cells can detect it.

27. Structure of cochlea if it could be uncoiled

28. Vibration of oval window causes vibration of perilymph of and which causes vibration of endolymph in

29. Vibration of the cochlear duct causes bending of hair cells within it. When these hair cells bend, they send electrical signals through the vestibulocochlear nerve to the brain

30. Hearing involves two aspects of bending hair cells: Which hair cells bend determines the pitch of the sound How far hair cells bend determines volume of the sound

31. The membranous labyrinth of the inner ear also houses the specialized receptor cells for equilibrium - both position of the head ("static equilibrium") and movement of the head ("dynamic equilibrium").

32. Special Senses Specialized Receptor Cells Specialized Organ..... TASTE: SMELL: VISION: HEARING: EQUILIBRIUM: Gustatory Cells Taste Buds Olfactory Cells Olfactory Epithelium Rods & Cones Eye (Retina) Hair Cells Cochlea

33. The parts of the membranous labyrinth responsible for equilibrium are the the and three which lie at right angles to each other.

34. The saccule and the utricle are responsible for detecting the position of the head ("static equilibrium"). Each of them contain a region of hair cells called a

35. The tips of these hair cells project into a gelatinous mass called the in which are embedded small crystals of calcium carbonate called

36. When the head changes position, gravity pulls on the otoliths, which causes the otolithic membrane to bend the hair cells (receptors) When these hair cells bend, they send electrical signals to the brain through the vestibulocochlear nerve, telling it the new position of the head

37. A very similar situation tells your brain about movement of the head when hair cells of the semicircular canals bend.

38. Each semicircular canal has an enlargement, or at one end where the hair cells (receptors) are located

39. The tips of these hair cells in an ampulla of a semicircular canal project into a gelatinous mass called the in which are also embedded

40. When the head moves in any direction, movement of the endolymph in the semicircular pulls on the otoliths, which causes the cupula to bend the hair cells (receptors) When these hair cells bend, they send electrical signals through the vestibulocochlear nerve to the brain, telling it which direction the head moved.

41. Special Senses Specialized Receptor Cells Specialized Organ..... TASTE: SMELL: VISION: HEARING: EQUILIBRIUM: Olfactory Cells Olfactory Epithelium Rods & Cones Eye (Retina) Hair Cells Cochlea Hair Cells Vestibular Apparatus

42. Most, but not all, taste buds are located on projections from the surface of the tongue called papillae Some taste buds are also located on the cheeks, the palate, and the oropharynx

43. Each taste bud contains three types of cells: Each taste bud also has a small hole, or taste pore, on its free surface (facing the inside of the mouth)

44. Each gustatory cell has long microvillus, called a gustatory hair, which extends out of the taste pore into the saliva of the mouth. This gustatory hair contains receptors on its plasma membrane which can detect specific chemicals in the saliva. At the other end, each gustatory cell is surrounded by dendrites of sensory neurons

45. Substances must be dissolved in saliva or other liquid before they can stimulate the gustatory cells. Each gustatory cell can respond to only one substance (sodium, glucose, etc.) BUT each taste bud contains many different types of gustatory cells. Gustatory cells for different types of tastes are grouped on different parts of the tongue

46. Each gustatory cell has a separate threshold: concentrations below this do not stimulate the receptors. In general: Sweet & Salty substances have high thresholds Sour substances have moderate thresholds Bitter substances have low thresholds

48. These afferent neurons carry information for conscious perception of tastes. They also form afferent limbs of reflexes whose efferent limbs stimulate saliva production, secretion of enzymes by stomach, liver, pancreas if necessary, gagging vomiting

49. Special Senses Specialized Receptor Cells Specialized Organ..... TASTE: SMELL: VISION: HEARING: EQUILIBRIUM: Gustatory Cells Taste Buds Rods & Cones Eye (Retina) Hair Cells Cochlea Hair Cells Vestibular Apparatus

50. The olfactory epithelium (mucosa) is located high in the nasal cavity, just inferior to the cribriform plate of the ethmoid bone.