1. Chapters 8 and11: Nonvisual Sensory Systems

2. Sensory Systems The brain detects events in the external environment and directs the corresponding behavior –Afferent neurons carry sensory messages to brain –Efferent neurons carry motor messages to the muscles Stimulus: any energy capable of exciting a receptor. This defines broad categories of sensory systems – Mechanical – Chemical – Thermal – Photic

3. Introduction Sensory Systems –What is the energy and how is it transduced? –What is the pathway to brain? –What common features does it share with other sensory systems?

4. Introduction: Chemoreceptors (gustatory and olfaction) Animals depend on the chemical senses to identify nourishment Chemical sensation –Oldest and most common sensory system Chemical senses –Gustation –Olfaction –Chemoreceptors

5. Taste The Basics Tastes –Saltiness, sourness, sweetness, bitterness, and umami –Examples of correspondence between chemistry Sweet—sugars like fructose, sucrose, artificial sweeteners (saccharin and aspartame) Bitter—ions like K + and Mg 2+, quinine, and caffeine –Advantage – Survival Poisonous substances - often bitter

6. Taste The Basic Tastes –Steps to distinguish the countless unique flavors of a food Each food activates a different combination of taste receptors Distinctive smell Other sensory modalities

7. Taste The Organs of Taste –Tongue, mouth, palate, pharynx, and epiglottis

8. Taste The Organs of Taste –Areas of sensitivity on the tongue Tip of the tongue –Sweetness Back of the tongue – Bitterness Sides of tongues –Saltiness and sourness

9. Taste The Organs of Tastes –Taste receptors –Threshold concentration Just enough exposure of single papilla to detect taste

10. Taste Tastes Receptor Cells –Apical ends  Microvilli  Taste pore –Receptor potential: Voltage shift

11. Taste Taste Receptor Cells

12. Taste Mechanisms of Taste Transduction –Transduction process Taste stimuli (tastants) –Pass directly through ion channels –Bind to and block ion channels –Bind to G-protein-coupled receptors

13. Taste Mechanisms of Taste Transduction –Saltiness Salt-sensitive taste cells – Special Na + selective channel Blocked by the drug amiloride

14. Taste Mechanisms of Taste Transduction –Sourness Sourness- acidity – low pH Protons causative agents of acidity and sourness

15. Taste Mechanisms of Taste Transduction –Bitterness Families of taste receptor genes - TIR and T2R

16. Taste Mechanisms of Taste Transduction –Sweetness Sweet tastants natural and artificial Sweet receptors –T1R2+T1R3 –Expressed in different taste cells

17. Taste Mechanisms of Taste Transduction –Umami Umami receptors: –Detect amino acids –T1R1+T1R3

18. Taste Central Taste Pathways –Gustatory nucleus Point where taste axons bundle and synapse –Ventral posterior medial nucleus (VPM) Deals with sensory information from the head –Primary gustatory cortex Receives axons from VPM taste neurons

19. Taste Central Taste Pathways (Cont’d) –Localized lesions Ageusia- the loss of taste perception –Gustation Important to the control of feeding and digestion –Hypothalamus –Basal telencephalon

20. Taste The Neural Coding of Taste –Labeled line hypothesis Individual taste receptor cells for each stimuli In reality, neurons broadly tuned Population coding –Roughly labeled lines –Temperature –Textural features of food

21. Difference between smell and pheromones? Smell (Olfactory)— a mode of communication –Important signals Reproductive behavior Mate Selection Territorial boundaries Identification Aggression –Pheromones Mate Selection Territorial boundaries Identification Aggression –Role of human pheromones

22. Pheromone Actions in Animals Pheromones are chemicals that transmit a message from one animal to another –Pheromones can alter reproduction Lee-Boot effect: the estrous cycle stops when groups of female mice are housed together Whitten effect: the estrous cycle restarts in synchrony when a group of female mice are exposed to the urine of a male mouse Bruce effect: involves the failure of pregnancy when a recently impregnated mouse is exposed to a normal male mouse (other than the one with which she mated) –The vomeronasal organ detects nonvolatile chemicals in urine The vomeronasal organ projects to the accessory olfactory bulb which in turn projects to the amygdala which has connections with the hypothalamus Lesions of the accessory olfactory bulb disrupt the Lee-Boot, Whitten and Bruce effects

23. Pheromone Actions in Humans Humans possess a vomeronasal organ Exposure to chemical present in sweat can alter human behavior –McClintock studied the menstrual cycles of women who attended an all-female college Women who spent time together showed synchronization of their menstrual cycles Women who spent time with men showed shorter cycles Exposure to underarm sweat elicited synchronization –Pheromones present in human sweat can alter social behavior Androstenol placed on a necklace had no effect on the social interactions of men, but women exposed to androstenol showed more interactions with me

24. Smell The Organs of Smell –Olfactory epithelium Olfactory receptor cells, supporting cells, and basal cells

25. Smell The Organs of Smell –Odorants: Activate transduction processes in neurons –Olfactory axons constitute olfactory nerve –Cribriform plate: A thin sheet of bone through which small clusters of axons penetrate, coursing to the olfactory bulb –Anosmia: Inability to smell –Humans: Weak smellers Due to small surface area of olfactory epithelium

26. Smell Olfactory Receptor Neurons –Olfactory Transduction

27. Olfactory Signal –Adaptation: Decreased response despite continuous stimulus Smell

28. Central Olfactory Pathways Smell

29. Central Olfactory Pathways (Cont’d) Smell

30. Central Olfactory Pathways (Cont’d) –Axons of the olfactory tract: Branch and enter the forebrain –Neocortex: Reached by a pathway that synapses in the medial dorsal nucleus Smell

31. Spatial and Temporal Representations of Olfactory Information –Olfactory Population Coding –Olfactory Maps (sensory maps) –Temporal Coding in the Olfactory System Olfaction paradox Smell

32. Concluding Remarks Transduction mechanisms – Gustation and olfaction Similar to the signaling systems used in every cell of the body Common sensory principles - broadly tuned cells –Population coding –Sensory maps in brain Timing of action potentials –May represent sensory information in ways not yet understood

33. The Nature of Sound Sound –Audible variations in air pressure –Sound frequency: Number of cycles per second expressed in units called Hertz (Hz) –Cycle: Distance between successive compressed patches –Range: 20 Hz to 20,000 Hz –Pitch: High and Low –Intensity: Difference in pressure between compressed and rarefied patches of air

34. The Structure of the Auditory System Auditory System

35. The Structure of the Auditory System Auditory pathway stages –Sound waves –Tympanic membrane –Ossicles –Oval window –Cochlea fluid –Sensory neuron response Brain stem nuclei output –Thalamus to MGN

36. Components of the Middle Ear The Middle Ear

37. Tonotopic Mapping

38. Sound Force Amplification by the Ossicles –Pressure: Force by surface area –Greater pressure at oval window than tympanic membrane, moves fluids The Attenuation Reflex –Response where onset of loud sound causes tensor tympani and stapedius muscle contraction –Function: Adapt ear to loud sounds, understand speech better The Middle Ear

39. Physiology of the Cochlea –Pressure at oval window, pushes perilymph into scala vestibuli, round window membrane bulges out The Response of Basilar Membrane to Sound –Structural properties: Wider at apex, stiffness decreases from base to apex Research: Georg von Békésy –Endolymph movement bends basilar membrane near base, wave moves towards apex The Inner Ear

40. The Organ of Corti and Associated Structures The Inner Ear

41. Transduction by Hair Cells –Research: A.J. Hudspeth. –Sound: Basilar membrane upward, reticular lamina up and stereocilia bends outward The Inner Ear

42. Central Auditory Processes Auditory Pathway Primary pathway: Ventral cochlear nucleus to superior olive to inferior colliculus to MGN to auditory cortex

43. Principles in Study of Auditory Cortex –Tonotopy, columnar organization of cells with similar binaural interaction The Effects of Auditory Cortical Lesions and Ablation –Lesion in auditory cortex: Normal auditory function (like vision?) –Lesion in striate cortex: Complete blindness in one visual hemifield –Different frequency band information: Parallel processing, localization deficit Auditory Cortex

44. Concluding Remarks Hearing and Balance –Auditory Parallels Visual System Tonotopy (auditory) and Retinotopy (visual) preserved from sensory cells to cortex code –Convergence of inputs from lower levels  Neurons at higher levels have more complex responses

45. Chapter 12: The Somatic Sensory System

46. Introduction Somatic Sensation –Enables body to feel, ache, chill –Sensitive to stimuli –Responsible for feeling of touch and pain –Somatic sensory system: Different from other systems Receptors: Distributed throughout Responds to different kinds of stimuli

47. Touch Types and layers of skin –Hairy and glabrous (hairless) –Epidermis (outer) and dermis (inner) Functions of skin –Protective function –Prevents evaporation of body fluids –Provides direct contact with world Mechanoreceptors –Most somatosensory receptors are mechanoreceptors

48. Touch Mechanoreceptors (Cont’d) –Pacinian corpuscles –Ruffini's endings –Meissner's corpuscles –Merkel's disks –Krause end bulbs

49. Touch Mechanoreceptors (Cont’d) –Receptive field size and adaptation rate

50. Touch Mechanoreceptors (Cont’d) –Two-point discrimination Importance of fingertips over elbow Primary Afferent Axons –A  C –C fibers mediate pain and temperature –A  mediates touch sensations

51. The Four Classes of Sensory Axons Differ in Size and Speed

52. Touch The Spinal cord –Spinal segments (30)- spinal nerves within 4 divisions of spinal cord –Dermatomes- 1-to-1 correspondence with segments Shingles

53. Touch The Spinal cord (Cont’d) –Sensory Organization of the spinal cord Divisions –Cervical (C) –Thoracic (T) –Lumbar (L) –Sacral (S)

54. Touch Spinal cord (Cont’d) –Sensory Organization of the spinal cord Division of spinal gray matter: Dorsal horn; Intermediate zone; Ventral horn –Myelinated A  axons (touch-sensitive)

55. Touch Dorsal Column–Medial Lemniscal Pathway –Touch information ascends through dorsal column, dorsal nuclei, medial lemniscus, and ventral posterior nucleus to primary somatosensory cortex The Trigeminal Touch Pathway –Trigeminal nerves –Cranial nerves

56. Dorsal Column- Medial Lemniscal Pathway

57. Touch Somatosensory Cortex –Primary –Other areas Postcentral gyrus Posterior Parietal Cortex

58. Touch Somatosensory Cortex (Cont’d) –Brodmann’s Area 3b (or S1): Primary somatosensory cortex Receives dense input from VP nucleus of the thalamus Neurons: Responsive to stimuli Lesions impair somatic sensations Electrical stimulation evokes sensory experiences

59. Touch Somatosensory Cortex –Cortical Somatotopy Homunculus Importance of mouth –Tactile sensations: Important for speech –Lips and tongue: Last line of defense

60. Touch Somatosensory Cortex (Cont’d) –S1: Rat Vibrissae “Barrel cortex”

61. Touch Somatosensory Cortex (Cont’d) –S1 – Owl monkey

62. Touch Somatosensory Cortex (Cont’d) –Cortical Map Plasticity –Remove digits or overstimulate – examine somatotopy before and after Conclusions of experiments –Reorganization of cortical maps »Dynamic »Adjust depending on the amount of sensory experience

63. Touch Somatosensory Cortex (Cont’d) –The Posterior Parietal Cortex Involved in somatic sensation, visual stimuli, and movement planning Agnosia Astereoagnosia Neglect syndrome

64. Pain Nociceptors Pain and nociception –Pain - feeling of sore, aching, throbbing –Nociception - sensory process, provides signals that trigger pain Nociceptors: Transduction of Pain –Bradykinin –Mast cell activation: Release of histamine

65. Pain Nociception and the Transduction of Painful Stimuli (Cont’d) –Types of Nociceptors Polymodal nocireceptors, Mechanical nocireceptors, Thermal nocireceptors –Hyperalgeia Primary and secondary hyperalgesia Bradykinin, prostaglandins, and substance P

66. Pain Primary Afferents and Spinal mechanisms –First pain and second pain –Referred pain: Angina

67. Pain Ascending Pain Pathways –Differences between touch and pain pathway Nerve endings in the skin Diameter of axons Connections in spinal cord –Touch – Ascends Ipsilaterally –Pain – Ascends Contralaterally

68. Pain Ascending Pain Pathways (Cont’d)

69. Pain The Regulation of Pain –Afferent Regulation –Descending Regulation –The endogenuos opiates Opioids and endomorphins

70. Pain The Regulation of Pain (Cont’d) –Descending regulation

71. Concluding Remarks Sensory systems exhibit similar organization and function Sensory represented in cortex Repeated theme – Parallel processing of information Perception of object involves the seamless coordination of somatic sensory information

72. End of Presentation