1. How brain receives information Prof. Vajira Weerasinghe Dept of Physiology www.slideshare.net/vajira54

6. Sensory pathway Receptor Sensory modality Sensory nerve Central Connections Ascending Sensory pathway Sensory area in the brain Touch stimulus AFFERENT

16. look like knotted balls of string in skin in border between dry skin and mucous membrane in mouth, genitals, anus Krause end bulbs hang under ridges of glabrous skin, small receptive fields, rapidly adapting Meissner's corpuscles small arrays of small disks which may have synapses to nerve endings, small receptive fields, slowly adapting Merkel's disks looks like small Pacinian, large receptive fields, slowly adapting Ruffini's ending nerve endings around root of hair in hairy skin, small receptive field, either slowly or rapidly adapting Hair follicle receptor looks like onion, large receptive field, rapidly adapting Pacinian corpuscles

17. Pacinian Corpuscle Capsule Nerve fibre

20. Transduction Stimulus Receptor potential (Generator potential) Action potential

21. Action Potentials Threshold Resting Membrane Potential -70 - 55 +30 Stimulus Receptor potential

23. Stimulus Receptor potentials Action potentials

27. Receptor potential generation in the Pacinian corpuscle

28. Pacinian corpuscle

29. Resting

30. Physical Stimulus Physical stimulus causing mechanical deformation on the capsule

31. Physical Stimulus Mechanical deformation is transmitted to the inside Opens up mechanosensitive Na+ channel Causes depolarisation and thus receptor potential

32. Physical Stimulus local current Current flow through a local circuit

33. Physical Stimulus Action Potentials are generated Opening of voltage gated Na+ channels causes generation of action potentials

36. Pacinian corpuscle Muscle spindle Pain Time Impulses per second

38. Impulse Stimulus Redistribution of pressure inside the capsule No Impulse Stimulus

42. Dorsal root Dorsal columns Dorsal horn Dorsal root ganglion Spinothalamic tracts Posterior (dorsal) Anterior (ventral)

43. Dorsal column pathway Spinothalamic pathway Lateral Spinothalamic tract Anterior Spinothalamic tract

45. Dorsal column nuclei (cuneate & gracile nucleus) Dorsal column Medial lemniscus thalamus thalamocortical tracts sensory cortex internal capsule 1st order neuron 2nd order neuron 3rd order neuron

49. Spinothalamic tracts thalamus thalamocortical tracts sensory cortex internal capsule 1st order neuron 2nd order neuron 3rd order neuron

53. Dorsal column pathway Spinothalamic pathway Lateral Spinothalamic tract Anterior Spinothalamic tract

63. Sensory homunculus

64. Brodmann areas

74. Lateral inhibition improves 2-point discrimination