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A 23 year old man is brought into the ER by his brother, demonstrating…

- - - - When two identical stimuli are delivered to a muscle in rapid succession, the second twitch will be stronger than the first
      - Occurs because the second contraction begins before the muscle has completely relaxed
      - Second contraction is greater because the muscle is still partially contracted
    - - Incomplete
        
        When the degree of wave summation is so great it has progressed to a sustained but quivering contraction
      - Complete
        
        Muscle reaches maximal tension and all evidence of muscle relaxation dissapears
        
        Contractions fuse into a smooth sustained contraction
    - - The response of a muscle to a single stimulation, muscle fibers contract quickly then relax
      - Three distinct phases
        
        Period of contraction
        
        Period of Relaxation
        
        Latent Period
  - - - Direct or Indirect
      - Secreted in CNS and PNS
      - Excitatory or Inhibitory depending on recetor
      - Acts as two classes of receptor
      - Prolonged blockage can lead to tetanic muscle spasms
    - - Generally Inhibitory
      - Direct and indirect actions via second messengers
      - Secreted in CNS
      - Principal inhibitory neurotransmitter in the brain
      - Blocking it's synthesis, release, or action induces convulsions
  - - - Drumstick shaped bacillus bacteria that releases tetanus toxin (tetanospasmin)
      - Commonly found in soil and is contracted through environmental exposure
      - Causes four different kinds of tetanus
        
        Generalized
        
        Most common type
        
        Symptoms: Lockjaw, spasms, convulsions, eventually leading to death from respiratory failure and cardiovascular instability
        
        Recovery can take months but can be done if caught early on enough
        
        Localized
        
        Very uncommon
        
        Muscle rigidity close to the site of injury
        
        Contractions can persist for weeks before dissapearing
        
        Cephalic
        
        Localized and effects cranial nerves
        
        Can happen after an ear infection or head injury
        
        Can effect facial muscles
        
        Neonatal
        
        Generalized tetanus that occurs in newborn infants
        
        90% fatality rate, common in developing countries
    - - C. tetani is taken up into the nerve terminals of lower motor neurons
      - Targets the protein VAMP which is necessary for the release of neurotransmitters at the nerve synapse
      - Initial symptoms are caused by interference with vesicular release of acetylcholine at the neuromuscular junction
      - Cuts off VAMP, inhibiting inhibiting the release of GABA and glycine
      - Results in partial, functional denervation of lower motor neurons leading to increased muscle activity in the form of rigidity and spasms