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Sensory System Chp 10

Sensory System Chp 10. Outline General considerations Somatic senses Smell and Taste Hearing and Equilibrium Vision. General properties. Stimulus  transduction into APs  CNS The type of receptor activated defines the type or modality of stimulation

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Sensory System Chp 10

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  1. Sensory System Chp 10 Outline General considerations Somatic senses Smell and Taste Hearing and Equilibrium Vision

  2. General properties • Stimulus  transduction into APs  CNS • The type of receptor activated defines the type or modality of stimulation • The receptors transform the stimuli into graded potentials  need adequate stimulation to reach threshold

  3. Table 10-2

  4. Somatic Mechanoreceptors: Touch, pressure, pain, equilibrium, hearing, proprioception Chemoreceptors: smell, taste Photoreceptors: vision Autonomic Baroreceptors: blood pressure Osmoreceptors: blood concentration Chemoreceptors: blood chemistry Types of receptors

  5. Anatomy of a basic receptor

  6. Receptive field: a receptor covers a certain area CNS integration: the number of neurons assigned to afferent impulses varies General properties

  7. Location: varies with the senses  touch: topographical arrangements of the receptors define the body location Sounds: difference in time of arrival in the brain helps to localize a sound Lateral inhibition: Helps sharpened the location of a stimulation How are location, Intensity and duration coded?

  8. How to code for intensity?The stronger the stimulus, the more frequent the APs

  9. Tonic receptors They fire as long as the stimulus is present Phasic receptors: they fire only when the strength of the stimulus changes How to code for duration?2 ways: Tonic and phasic receptors

  10. Receptors (touch, pain, pressure) send an APs through 1st sensory neuron (where is the body of this neuron?) Relay and crossing over in MO (2nd sensory neuron) Relay in thalamus before projection on the primary sensory cortex in parietal lobe. Associated sensory cortex helps give a meaning to the sensation Somatic senses

  11. Figure 10-11

  12. Figure 10-10

  13. Figure 10-4 - Overview

  14. Many qualities to pain - superficial / deep - sharp / dull Several modes of control Abnormalities: - referred pain  - phantom pain Pain

  15. Conduction of pain • Sharp, superficial pains are conducted fast • Dull, visceral pains are conducted through slower axons

  16. Perception of pain is modulated by past experiences Minor stimulations will be blocked; stronger one will be allowed to continue to the brain Gate control theory of pain  other touch sensation can block pain APs from going to the brain Control of pain

  17. Organ: the nose Receptors: Olfactory receptors (many different ones) Pathway: Olfactory receptors olfactory bulbs  Olfactory nerve  Olfactory cortex in lower frontal lobe (+ amygdala and hippocampus) Smell

  18. Organ: Tongue (papilla) Receptors: taste buds (5 different ones: ?), specialized epithelial cells Pathway: receptors  nerves (VII-IX-X)  MO  thalamus gustatory cortex (base of parietal lobes) Taste Figure 10-14 - Overview

  19. How is the taste signal transduced into APs?

  20. Organ: the ear  cochlea Receptors: Organ of Corti Pathway: Receptors  cochlear nerve  MO  thalamus  auditory cortex in temporal lobes Hearing

  21. Figure 10-20 – Overview (1 of 8)

  22. The louder the noice the more frequent will be the APs sent through the cochlear nerve How to code for sound intensity?

  23. How is the pitch of a sound coded?

  24. Two types: Linear acceleration and head position controlled by the maculas from the Utricle and Saccule Rotational equilibrium controlled by the Cristaes ampullaris from the semi-circular canals Equilibrium

  25. Figure 10-23b

  26. The stereocilia are sensitive to pulling In upright position, one of the macula is firing, the other one is quiet In horizontal position, the firing pattern is reversed Head position and linear acceleration

  27. Controlled by the 3 semi-circular canals They act as 3 spatial axes: X, Y, and Z The receptor, crista ampullaris, fired when its cilia are pulled (by movement) Rotational equilibrium

  28. Pathway for equilibrium

  29. What happens during sea-sickness

  30. Organ: Eye Receptors: photoreceptors Pathway: Optic nerve  Optic chiasmata  thalamus (lateral geniculate nucleus)  Visual areas of occipital lobe Vision

  31. Figure 10-28 - Overview

  32. Pathway

  33. Accommodation (focus)

  34. Accommodation

  35. Figure 10-33 - Overview

  36. What are? • Glaucoma • Cataract • Retinal detachment

  37. Transduction of visual signals

  38. Figure 10-35 - Overview (1 of 2)

  39. Figure 10-35d

  40. Figure 10-35e

  41. Figure 10-36

  42. Figure 10-37 - Overview (1 of 6)

  43. Figure 10-38

  44. Photoreceptor activation

  45. Figure 10-41

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