receptors in skin. the structure and function of the pacinian corpuscle as an example of...
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Receptors in Skin
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The Structure and Function of the Pacinian Corpuscle as an example of transduction of mechanical to action potentials
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Properties of Skin Receptors Related to Touch
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Various Touch Receptors Responding to Braille
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Table 8.2 Fibers That Link Receptors to the CNS
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Somatosensory Pathways
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Representation of the Body Surface in Somatosensory Cortex (Part 1)
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The Columnar Organization of the Somatosensory Cortex
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Doesn’t That Hurt?
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The Multifaceted Character of Pain
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Peripheral Mediation of Pain
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Receptors That Detect Pain and Temperature
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Pain ascends the spinothalamic system to reach the brain
Synapse here
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Ascending and Descending Pain Pathways
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Filelds et al Nature NeuroscienceReviews 2004
STATE-DEPENDENT OPIOID CONTROL OF PAINFields et al Nature Neuroscience Reviews VOLUME 5, 565-575 2004
Pain Pathways
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Types of Pain Relief Intervention
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Social Rejection Activates Brain Regions for Affective Pain
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Placebo effects terminology
• Placebo is Latin for “I will please”• An inert substance or treatment that does not have a
direct physiological effect – The original meaning: 1950: The effect of a placebo treatment – The alternative meaning: 1960-80: The effect of the interaction
between the patient and the health provider
• Belief in the beneficial nature of the treatment• a key component of the true placebo effect• enhanced by factors such as
• interaction with the physician• sensory impact of the treatment
• Negative beliefs can generate a nocebo effect• may explain some psychogenic illnesses• basis of much research in psychoneuroimmunology
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Placebo Effects• Placebos have effect on
– subjective and objective outcomes– in a large proportion of patients– with a wide range of clinical conditions such as
• Pain• Asthma• Survival after myocardial infarction• Hypertension• Colds
• Used in research trials to objectively test the efficacy of new treatments
• One group is given the treatment, while another group (the control group) receives a placebo
• Comparing the results from both groups should reveal the effects of the treatment
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Placebo Response Mechanisms• Examples of pain relief “analgesia” from placebo• Expectation “belief” in treatment• Activation of opiate based descending control system
– 30 – 50 % get some analgesia
– can be blocked by naloxone an opiate antagonist
• Expectation produces increased activity during anticipation of pain in the prefrontal cortex
• Decreased activity in the thalamus, insula, and anterior cingulate cortex
• Probably a frontal cortex activation of areas in the cingulate cortex which then activates the PAG midbrain areas
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Placebo Response Mechanisms• Expectation from:
– Conditioning: previously experiencing the benefit – Social learning: observing others produces similar placebo
responses to conditioning– Verbal suggestions: alone produces smaller effects
• Problem of no “untreated”control group – effect consists of two components– nonspecific effects (eg, natural recovery)– a "true placebo effect" that is the psychological therapeutic
effect of the treatment– So effect of placebo is not isolated from
• spontaneous remission• regression to the mean• other factors