1 Receptors of Somatic Sensation n Mechanoreceptors of the skin –Free nerve ending –Merkel’s disk –Meissner’s corpuscle –Pacinian corpuscle –Hair follicle receptor

2 Mechanoreceptors of the skin n Testing –Receptive field –Two point discrimination –Frequency sensitivity –Vibration and the Pacinian corpuscle

3 Nociception n Receptors –Mechanical –Thermal –Chemical –Polymodal

4 Thermoreception n Warm receptors n Cold receptors

5 Proprioception n Joint receptors n Muscle receptors –Golgi tendon organs –Muscle spindles

6 Stevens’ Rule n I=k(S-S 0 ) n –I=Sensation intensity –k=Proportionality constant –S=Stimulus intensity –S 0 =Threshold stimulus intensity

7 Primary Afferent Nerves n Proprioceptors: A , large and fast n Mechanoreceptors of skin: A , intermediate size and speed n Pain, Temperature: A , intermediate size and speed n Pain C: Small and slow and unmyelinated

8 Ascending Pathways of Somatic Sensation n Dorsal column/medial lemniscal pathway n Spino-thalamic path

9 Organization of the Spinal Cord