1. 1-7 are Anterior median fissure, Anterior (ventral) root, Central canal, Posterior (dorsal) root, Posterior (dorsal) root ganglion, Posterior median sulcus, or Spinal nerve
2. 1-4 are Astrocytes, Microglial cell, Oligodendrocyte, Ependymal cell, satellite cell, or Schwann cell (two are not used)
3. 1-12 are Anterior gray horn, Anterior median fissure, Anterior (ventral) root, Anterior white column, central canal, gray commissure, lateral white column, posterior (dorsal) root, posterior (dorsal) root ganglion, posterior gray horn, posterior white column, or posterior median sulcus
4. 1-8 are Graded potential starts in a sensory receptor in the skin. A synapse in the thalamus creates a graded potential followed by an action potential in a secondary interneuron, which reaches the cerebral cortex. The graded potential triggers an action potential in a sensory neuron. The lower motor neuron forms a neuromuscular synapse with the hand muscles, which causes the muscles to contract as her writes the letter. In another synapse, the neurotransmitter creates a graded potential, which triggers an action potential in the lower motor neuron. A primary interneuron forms an action potential and crosses to the opposite side of the brain. A stimulus from the brain causes a graded potential and then an action potential to form in an upper motor neuron (which crosses back to the original side of the body). At a synapse, a presynaptic sensory neuron stimulates the postsynaptic interneuron to form a graded potential in its cell body.