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Nervous System (Membrane Potentials (MP) (Basic Principle of Electricity…

- - - - Short-lived signals operating over short distances
      - Named according to location and function
        
        Receptor (generator) potentials
        
        Postsynaptic (neuron) potentials
      - Triggered by stimulus that opens gated ion channels. Results in depolarization that spreads from one area of the membrane to the next.
    - - Long-distance signals of axons
    - - Depolarization : Decreases MP (more positive)
      - Hyperpolarization Increases MP (more negative)
  - - - Chemically gated channels require binding of specific chemical (neurotransmitter)
      - Voltage gated channels respond to changes in MP
      - Mechanically gated channels respond to physical deformation of (sensory) receptors
      - When gated channels open, ions diffuse quickly from high to low concentration, creating an electrical current and voltage changes
  - - - Differences in plasma membrane permeability
        
        Slightly permeable to Na+
        
        25x more permeable to K+. As a result, inside of the cell is more negative
        
        Sodium-potassium pump (Na+/K+ ATPase) restabilizes resting membrane potential. (3 Na+ pumped out for every two K+ pumped back in)
        
        Impermeable to large anionic proteins
      - Differences in ionic composition
        
        ICF has higher concentration of K+ than ECF (balanced by negatively charged proteins)
        
        ECF has higher concentration of Na+ than ICF (Balanced by Cl-)
- - - - Somatic and Visceral sensory nerve fibers: Conduct impulses from receptors to the CNS
    - - Motor nerve fibers: Conduct impulses from the CNS to effectors (muscles and glands)
      - Somatic Nervous System (Voluntary): Conducts impulses from CNS to skeletal muscles
      - Autonomic Nervous System (Involuntary): Conducts impulses from CNS to glands, cardiac and smooth muscle
        
        Sympathetic Division: Mobilizes (fight or flight)
        
        Parasympathetic: house-keeping functions (rest and digest)