Sensory System

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Author:
fruitpunch
ID:
294222
Filename:
Sensory System
Updated:
2015-01-28 22:02:58
Tags:
Sensory
Folders:
Physiology
Description:
Sensory System
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  1. Sensory systems
    Part of the nervous system that consists of sensory receptors that receive stimuli from the external/internal environment, neural pathways that conduct info from receptors to brain/spinal cord, processing areas
  2. Stimulus Detection
    • Adequate stimulus needed
    • Particular receptor may respond best to a limited subset of stimuli
  3. Transduction
    • Converting signal in environment to electrical signal in NS
    • Opening/cloing of ion channels that receive information about the internal & external world (Directly/indirectly)
  4. Types of sensory receptors
    • Sensory receptors that are specific for a stimulus:
    • Chemoreceptors(Chemical signals)
    • Mechanoreceptors(Movement, pressure)
    • Photoreceptors(Light)
    • Thermoreceptors (Temperature)

    • Non-specific:
    • Nociceptors (Intense temp, pressure, chemicals)
  5. Nociceptors
    • Pain fibers
    • Not specific about type of input received
    • Respond to intense temp, pressure, chemicals
  6. Role of graded potentiaals in transduction(Receptor Potentials)
    As long as a receptor potential keeps afferent neuron depolarized to a level at/above threshold. AP will fire and propogate along neuron
  7. Labeled Line Coding
    Unique pathways to a specific region of CNS, association only with that particular modality/body location
  8. Acuity
    • Precision
    • More convergence--> Less acuity
  9. Receptive Field Size
    The area of the body that leads to activity in a particular afferent neuron when stimulated
  10. Lateral Inhibition
    Method of refining sensory information in afferent neurons and ascending pathways whereby fibers inhibit each other, the most active fibers causing greatest inhibition of adj.  fibers (in CNS)
  11. How is acuity improved?
    receptor field size & lateral inhibition
  12. Tonic(Slowly Adapting)
    • As long as stimulus there, neuron will respond keep firing
    • Eventually neuron ceases responding to stimulus -->Adaptation
    • Examples:Pain fibers, Blood Pressure
  13. Phasic
    • Rapidly adapting
    • Responds for short periods of time
    • Pressure fibers
    • Convey info about changes¬†
    • CNS inhibiting to somatosensory cortex
    • Example: Touch fibers
  14. Referred Pain
    • Feeling pain on body surface in response to eneteric neurons which converge on this body surface's labeled line
    • Example: Heart attack
  15. Phantom Limb
    Activation of neural networks can cause perception of sensation in missing limb
  16. Range Fractionation
    No sensory neuron can detect/respond quantitavely to all stimuli
  17. Adequate Stimulus
    Each type of sensory receptor has preferred stimulus
  18. Autonomic Nervous System
    • 2-chain neurons (connected by synapse) between CNS/effector organ
    • Innervates smooth/cardiac muscle, GI neurons but NOT skeletal muscle
    • Excitatory/Inhibitory
    • Controls internal organs & maintains homeostasis
  19. Sympathetic Division
    • Preganglionic fibers leave CNS at thoracic/lumbar portions of spinal cord
    • Most ganglia are close to the spinal cord
    • Chromaffin Cells in Adrenal Medulla which stimulate adrenergic receptors near and far from sympathetic postganglion neurons
    • Postganglionic neurons release norephinephrine
  20. Parasympathetic Division
    • Rest & Digest (Decrease heart rate)
    • Preganglionic fibers leave CNS brain stem & sacral portion of spinal cord
    • Most pre-ganglionic fibers release Ach
    • Cranialsacral
  21. Chromaffin Cells
    • In Adrenal Medulla
    • Axon inhibited during development
    • Releases 80% E & 20% NE into bloodstream as hormones, stimulating adrenergic receptors near and far from sympathetic postganglion neurons
    • Postganglionic neurons release norepinephrine

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