Psychophysical laws. Legge di Fechner: I=K*log(S/S 0 )

Transcription

1 Psychophysical laws Legge di Weber: ΔS=K*S Legge di Fechner: I=K*log(S/S 0 )

2 Sensory receptors Vision Smell Taste Touch Thermal senses Pain Hearing Balance Proprioception

3 Sensory receptors Table 21-1 Classification of Sensory Receptors Sensory system Modality Stimulus Receptor class Receptor cells Visual Vision Light (photons) Photoreceptor Rods and cones Auditory Hearing Sound (pressure waves) Vestibular Head motion Gravity, acceleration, and head motion Somatosensory Touch Proprioception Pain Skin deformation and motion Muscle length, muscle force, and joint angle Noxious stimuli (thermal, mechanical, and chemical stimuli) Mechanoreceptor Mechanoreceptor Mechanoreceptor Mechanoreceptor Thermoreceptor, mechanoreceptor, and chemoreceptor Hair cells in cochlea Hair cells in vestibular labyrinths Cranial and dorsal root ganglion cells with receptors in: Skin Itch Histamine Chemoreceptor Skin Visceral (not painful) Wide range (thermal, mechanical, and chemical stimuli) Thermoreceptor, mechanoreceptor, and chemoreceptor Gustatory Taste Chemicals Chemoreceptor Taste buds Muscle spindles and joint capsules All tissues except central nervous system Gastrointestinal tract, urinary bladder, and lungs Olfactory Smell Odorants Chemoreceptor Olfactory sensory neurons

4 Spatial resolution

5 Somatosensory afferents convey information from the skin surface to central circuits

6 The skin harbors a variety of morphologically distinct mechanoreceptors

7 Transduction in a mechanosensory afferent (a Pacinian corpuscle)

8 Receptive fields and two-point discrimination threshold (Part 1)

9 Receptive fields and two-point discrimination threshold

10 Slowly and rapidly adapting mechanoreceptors respond differently to a stimulus

11 Proprioceptors provide information about the position of body parts

12 Schematic representation of the main mechanosensory pathways

13 Schematic representation of the main mechanosensory pathways

14 Lateral inhibition A Neural circuits for sensory processing C Types of inhibition in relay nuclei Stimulus Skin Somatosensory cortex Receptors Output to thalamus Neurons in relay nucleus Feedback Feed-forward Descending B Spatial distribution of excitation and inhibition Stimulus To spinal cord Receptors Frequency Relay neurons

15 Somatic sensory portions of the thalamus and their cortical targets in postcentral gyrus

16 Somatotopic order in the human primary somatic sensory cortex

17 Connections within the somatosensory cortex establish functional hierarchies

18 Neurons in the primary somatosensory cortex form functionally distinct columns

19 Functional expansion of a cortical representation by a repetitive behavioral task

20 Properties of SII neurons

21 Thermoception

22 Experimental demonstration that nociception involves specialized neurons

23 Pain can be separated into first (sharp) and second (duller, burning) pain

24 The anterolateral system

25 The anterolateral system sends information to different parts of the brainstem/forebrain

26 Inflammatory response to tissue damage

27 Enhanced excitability of dorsal horn neurons A Repetitive stimulation of C and A fibers 80 Aδ fiber C fiber B Number of spikes Response to C fiber Response to Aδ fiber Stimulus number B Enhancement of excitability Aδ fiber stimulation C fiber stimulation Glutamate Substance P AMPA AMPA NMDA AMPA NMDA NMDA NK1 Ion channels Ca 2+ Ca 2+ Fast membrane depolarization (transient) Long-lasting depolarization (cumulative)

28 Descending systems that modulate the transmission of ascending pain signals

29 Descending systems that modulate the transmission of ascending pain signals

30 Descending systems that modulate the transmission of ascending pain signals

31 Referred Pain