Physiology of the sensory system

1. Physiology of the sensory system

2. Types of Sensory Receptors • Mechanoreceptors • detect deformation • Thermoreceptors • detect change in temperature • Nociceptors • detect damage (pain receptors) • Electromagnetic • detect light • Chemoreceptors • taste, smell

3. Classification of Somatic Sensations • mechanoreceptive - stimulated by mechanical displacement. • tactile • touch • pressure • vibration • tickle and itch • position or proprioceptive • static position • rate of change

4. Classification of Somatic Sensations • thermoreceptive. • detect heat and cold. • nociceptive. • detect pain and are activated by any factor that damages tissue.

5. Receptor Potential • the membrane potential of the receptor. • excitation of the receptor results from a change in this potential. • when the receptor potential rises above the threshold, action potentials appear and the receptor is active. • the greater the intensity of the stimulus, the greater the receptor potential, and the greater the rate of action potential generation.

6. Relationship between receptor potential and action potentials Figure 46-2

10. Sensory

11. Types of sensation • types of sensations • General sensation • Somatic • Special senses • Smell, taste, vision etc exteroceptor Proprioceptor : muscle length and tension, joint position and their motion

12. Sensations modalities PCML Temperature Crud touch (itch & rub) Pain ALS • Prorioception • Fine touch & pressure • Vibration Posterior Column-Medial lemniscus Pathway (PCML)

13. PCML Pathway

14. ALS Pathway

17. Relationship Between Receptive Fields and Cortical Representation Text Fig. 17-3 Text Fig. 17-12 Inverse relationship in the cortex. Smaller the receptive fields larger the cortical area Larger the receptive fields smaller the cortical area Smaller the receptive fields, greater the density of receptors.This relationship allows for greater discrimination in sensory inputs.

18. Conduction speed • Number of synapses • Myelination • Nerve axon size

20. Visceral sensory & referred pain

21. Visceral sensory & referred pain

22. Visceral sensory & referred pain

23. Visceral sensory & referred pain

24. Referred pain right Left liver

25. Somatosensory in the face (Trigeminal system)

26. (Trigeminal system) • Carry all the sensation modalities from the face to the brain

27. (Trigeminal system) • Carry all the sensation modalities from the face to the brain