Expand on the three major kinds of neurons and their functions (hint: motor neurons, sensory neurons, and interneurons). Each play a different role, but they all have the same basic components and operate the same way. How is this possible? Elaborate further on the role of the neural membrane and electric polarization (resting potential, graded potential, and action potential) and the role of the sodium-potassium pump in maintaining forces of diffusion. What is the refractory period and how does this limit the neuron's firing potential? What role do glial cells provide with regard to conduction and regulation of activity in the neurons? Lastly, how do neurons communicate with each other through the use of neurotransmitters? What happens to leftover neurotransmitter in the presynaptic space