9e87a33e63ca216ce9ee5f09d8278efa.ppt
- Количество слайдов: 35
Neuroscience: Exploring the Brain, 3 e Chapter 12: The Somatic Sensory System Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Introduction • Somatic Sensation – Enables body to feel, ache, chill – Responsible for touch and pain – Somatic sensory system: Different from other systems • Receptors: Broadly distributed • Responds to many kinds of stimuli Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Types and layers of skin – Hairy and glabrous (hairless - e. g. , palms) – Epidermis (outer) and dermis (inner) • Functions of skin – Protective – Prevents evaporation of body fluids – Provides direct contact with world • Mechanoreceptors – Most somatosensory receptors are mechanoreceptors Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Mechanoreceptors (Cont’d) – Pacinian corpuscles – Ruffini's endings – Meissner's corpuscles – Merkel's disks – Krause end bulbs Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Mechanoreceptors (Cont’d) – Small and large receptive fields Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Mechanoreceptors (Cont’d) – Receptors - receptive field size and adaptation rate Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Mechanoreceptors (Cont’d) – Two-point discrimination • Receptive field density • Receptive field size • Computing power • Special neural mechanisms Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Primary Afferent Axons – Aa, Ab, Ad, C – C fibers mediate pain and temperature – Ab mediates touch sensations - Ad mediates acute, early pain Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • The Spinal cord – Spinal segments (30)- spinal nerves within 4 divisions of spinal cord. Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Spinal cord (Cont’d) – Divisions of spinal gray matter: Dorsal horn; Intermediate zone; Ventral horn • Myelinated Ab axons (touch-sensitive) Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Dorsal Column–Medial Lemniscal Pathway – Touch and proprioception Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • The Trigeminal Touch Pathway – Somatosensory information from face Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Somatosensory Cortex – S 1 = Area 3 b – Adjacent areas: • Postcentral gyrus: 3 a, 1, 2, • Posterior Parietal Cortex: 5, 7 Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Somatosensory Cortex – Cortical Somatotopy: Homunculus Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Somatosensory Cortex (Cont’d) – S 1: Rat“Barrel cortex” (vibrissae) Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Somatosensory Cortex (Cont’d) – 3 b and 1 – Two mirror image maps - Owl monkey Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Somatosensory Cortex (Cont’d) – Cortical Map Plasticity – Remove digits or overstimulate – examine somatotopy before and after – Maps are dynamic Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • Somatosensory Cortex (Cont’d) – The Posterior Parietal Cortex • Involved in somatic sensation, visual stimuli, and movement planning • Agnosia • Astereoagnosia • Neglect syndrome Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Pain • Nociceptors • Pain and nociception – Pain - feeling of sore, aching, throbbing – Nociception - sensory process, provides signals that trigger pain • Nociceptors: Transduction of Pain – Mechanically gated ion channels opened by: • Strong mechanical stimulation, temperature extremes, oxygen deprivation, chemicals – Damaged cells release substances that open ion channels • Proteases (-> bradykinin), STP, K+ ion channels • Histamine Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Pain • Nociception and the Transduction of Painful Stimuli (Cont’d) – Types of Nociceptors • Polymodal • Mechanical • Thermal – Hyperalgeia • Primary and secondary Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Pain • Primary Afferents and Spinal mechanisms – First pain and second pain – Referred pain: Angina Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Pain • Ascending Pain Pathways Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Pain • Ascending Pain Pathways – Touch and pain systems segregated • Nerve endings in the skin • Diameter of axons • Connections in spinal cord • Touch – Ascends Ipsilaterally • Pain – Ascends Contralaterally – Brown-Séquard Syndrome – Trigeminal Pain Pathway Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Pain • Ascending Pain Pathways (Cont’d) Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Pain • Pain Regulation – Afferent Regulation – Gate theory of pain - Melzack and Wall Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Pain • Pain Regulation – Descending Regulation -> – The endogenous opiates • Opioids and endomorphins Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Temperature • Thermoreceptors – “Hot” and “cold” receptors – Varying sensitivities Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Temperature • Thermoreceptors – Hot and cold receptors Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Temperature • The Temperature Pathway – Organization of temperature pathway • Identical to pain pathway – Cold receptors coupled to Ad and C – Hot receptors coupled to C Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Concluding Remarks • Sensory systems exhibit similar organization and function • Somatic sensory information segregated within the spinal cord and cerebral cortex – Parallel processing of information • Perception of object involves the seamless coordination of somatic sensory information Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
End of Presentation Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Touch • The Spinal cord – Dermatomes- 1 -to-1 correspondence with segments – Shingles Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
9e87a33e63ca216ce9ee5f09d8278efa.ppt