sensory and motor systems

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• Sensory and Motor Systems

  Systems specialized in detecting and responding to stimuli
• Describe the role of the sensory and motor system in vertebrates

  
• How external stimuli are transduced into nerve signals

  1. Touch

  2. Hearing

  3. Sight

  4. Taste and smell

  
• Describe features of the motor system and explain how skeletal muscles relax/contract
• Describe the types of support the motor system has in humans
• Sensory and motor systems overview

  • Sensory input → integration → motor output
  • Specialized cellular receptors (mechanical, electromagnetic, chemical, temperature, pain)
  • Specialized sensory organs (ears, eyes, nose, skin, etc.)
  • Specialized motor tissues (muscle)
  • Specialized support tissues (skeleton)

  
• Sensory pathways


  • Reception: specialized receptors receive external stimuli as some form of energy
  • Transduction: stimulus is converted into electrical signal (change in membrane potential)
  • Transmission: passage of electrical energy via neurons
  • Integration: CNS and ganglia receive electrical signals from neurons and perception occurs

  
• Sensory input undergoes amplification and adaptation


  • Amplification: strengthening of stimulus energy by cells in sensory pathways
  • Adaptation: decrease in responsiveness to continued stimulation

  
• Sensory receptors


  • Mechanoreceptors
  • Chemoreceptors
  • Electromagnetic receptors
  • Thermoreceptors
  • Pain receptors (nociceptors)
• Sensory organs


  • Skin
  • Ears
  • Eyes
  • Tongue
  • Nose

  
• Touch: mechanoreceptors


  Mechanically-gated ion channels
• Hearing


  Results from activation of mechanoreceptors in the ear

  
• Vision


  Detects electromagnetic energy waves with photoreceptors
• Gustation (taste)


  Chemoreceptors in the tongue and mouth

  
• Olfaction


  Chemoreceptors in the nose
• Musculoskeletal system: motor function
• Skeletal muscle


  Muscle cells work by contracting using interactions between protein filaments
• Muscle contraction: sliding-filament model


  Motor neuron signal induces calcium release and subsequent muscle contraction
• Motor unit


  Consists of a single motor neuron and all the muscle fibers it controls
• Classification of skeletal muscle fibers

  • Oxidative versus glycolytic

  Fast-twitch versus slow-twitch
• Cardiac muscle


  Found in heart; consists of striated cells electrically connected by intercalated disks
• Smooth muscle


  Found mainly in walls of hollow organs such as the digestive tract, contractions are relatively slow and may be initiated by muscles themselves
• Skeletal systems: support and movement
• Types of skeletal systems

  • Hydrostatic

  Exoskeletons

  Endoskeletons
• Connective Tissue


  Tendon: fibrous tissue connecting muscle to bone

  Ligament: fibrous tissue connecting bone to bone
• slow twitch fibers contract more slowly but sustain longer contractions; oxidative
• fast twitch fibers contract more rapidly but sustain shorter contractions; glycolic or oxidative