Nerve cells and nerve impulses

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Across
  1. 3. remove waste materials, viruses from the brain
  2. 5. gate the ion gate that do not close completely
  3. 8. send impulses to a muscle
Down
  1. 1. the first ion gate that opens to start action potential
  2. 2. the jumping of an action potential from node to node
  3. 4. a type of refractory period where stimulus stronger than usual is required to trigger an action potential
  4. 6. a type of refractory period where the membrane cannot produce an action potential
  5. 7. wraps the axon