2. © 2012 Pearson Education, Inc. Chapter 15 Neural Integration I: Sensory Pathways and the Somatic Nervous System

3. © 2012 Pearson Education, Inc. Sensory Receptors Detect info about external/internal environment 3 classifications of sensory receptors: Interoceptors: monitor internal environment Exteroceptors: monitor external environment Proprioceptors: monitor position of muscles/joints Stimulus translated to AP  CNS = transduction

4. © 2012 Pearson Education, Inc. Simple vs. Complex Receptors Simple receptors dendrites of sensory neurons Branching tips of dendrites = free nerve endings Not protected by accessory structures Little specificity (i.e.: free nerve endings respond to stimulus caused by chemicals, pressure, temperature or trauma) Complex receptors Found in sense organs Example: eye’s visual receptors Protected by accessory cells and CT Specific (i.e.: receptors cells in eye are protected by accessory structures and CT, usually only stimulus reaches these cells is light)

5. © 2012 Pearson Education, Inc. Tonic vs. Phasic Receptors Tonic Always active A.k.a slow-adapting receptors: little change in receptor activity over time Indicates background level of stimulation Phasic Normally inactive Provide info about intensity and rate of change of stimulus A.k.a. fast-adapting receptors: respond strongly at first, activity declines

6. © 2012 Pearson Education, Inc. Receptive field 1 Receptive field 2 Receptive field: area monitored by single receptor Larger field=harder to localize stimulus Receptor specificity: receptors sensitive to specific stimuli Examples: Touch receptors sensitive to pressure, not chemical stimuli Taste receptors sensitive to chemicals, not pressure stimuli Sensation: arriving information from receptors via AP Perception: conscious awareness of sensation

7. © 2012 Pearson Education, Inc. Interpretation of Sensory Information Sensory neurons relay info from receptor to specific cortex areas Link between receptor and cortical neuron = labeled line Axons of labeled line carry info about 1 type of stimulus (modality) Sensory coding = translation of complex sensory info into meaningful patterns of AP CNS interprets modality based on labeled line Cannot tell difference between true/false sensation i.e.: rub eyes = mechanical stimulus causes visual of flashes of lights; any activity along optic nerve travels to visual cortex = visual perception

8. © 2012 Pearson Education, Inc. Nociceptors Tonic Locations: superficial portions of skin Joint capsules Periosteum Walls of BVs Detects: pain Myelinated Type A fibers: fast or prickling pain (i.e.: injection or deep cut) Type C fibers: slow or burning/aching pain

9. © 2012 Pearson Education, Inc. Thermoreceptors Phasic Free nerve endings in dermis, skeletal muscles, liver and hypothalamus More cold than warm Carried along same pathway as pain sensations Info sent to Thalamus reticular formation of midbrain Primary sensory cortex

10. © 2012 Pearson Education, Inc. Mechanoreceptors Stimulus caused by distortion of plasma membranes Three classes: Tactile (touch, pressure, vibration) Baroreceptors (pressure changes in BVs) Proprioceptors (position of joints/skeletal muscles)

11. © 2012 Pearson Education, Inc. Types of Tactile Receptors Tonic; small receptive fields Located between epidermal cells Sensitive to touch/pressure Phasic Respond rapidly Best at detecting initial contact and subsequent movement Tonic; small receptive fields Extremely sensitive Found in stratum basale

12. © 2012 Pearson Education, Inc. Types of Tactile Receptors Tonic Located in dermis pressure Aka: Meissner’s Phasic Locations: eyelids, lips, fingertips, nipples, external genitalia Fine touch/pressure or low frequency vibrations Phasic Deep pressure Provides somatic and visceral sensory info

13. © 2012 Pearson Education, Inc. Chemoreceptors Only respond to water or lipid soluble substances dissolved in body fluids Info sent to brain stem (i.e. respiratory and cardiovascular centers), not cortex Located in: carotid and aortic bodies monitor pH, CO2 and O2 levels