Identify what parts of the body would be considered series and what parts would be considered parallel.
The  best example of how the body would be considered series and parallel is  the central nervous system, which include the brain and the spinal  cord. The nervous system sends messages back and forth from the brain  (power source), through the spinal cord and to the nerves throughout the  body. The brain sending signals down the spinal cord would be  considered series. Signals are sent through the peripheral nerves and to  the muscles, glands and organs throughout the body would be considered  parallel. 
Discuss how the series and parallel systems function together as a series-parallel circuit in your analogy.
The  brain, which would be the power supply, sending signals down the spinal  cord would be the series system. The body cannot function without the  brain sending signals through the spinal cord and to the rest of the  body, which makes it analogous to a series circuit. Signals sent from  the spinal cord to the peripheral nerves would be the parallel system  because one side can function independently from the other. 
Explain how electricity can travel through the  body using a series-parallel electrical model. How does this relate to  touch, step, and step-touch potential?
Let’s say that there  is a broken overhead power line and it makes contact with the ground  while it is still energized. The touching point of the power line and  the ground has now produced a huge potential value, and everything  within a 10 meter radius of the contact could also be energized.  Electricity spreads like ripples or rings over the surface of the ground  away from the point of contact. Each “ring” carries a different  potential value. If you step in one ring while your other foot is in  another, this different potential values on both legs will cause the  electrons to travel through your body from high potential to low  potential which results in an electric shock (SCGA, 2019). This is an  example of step potential.
If you touch a vehicle, or any other  object, that is in contact with the broken power line, this will cause a  potential difference between hand (high potential) and leg (low  potential). The electricity will travel through your body to get to the  ground (SCGA, 2019). This is an example of touch potential. 
Finally, Discuss the loading effect of a  voltmeter on a circuit. How does the voltmeter’s internal resistance  affect the loading effect?
The loading effect of a voltmeter  is the difference between actual voltage that exists in the circuit  without connecting the voltmeter and the voltage that appears after  connecting a voltmeter (EEE, 2019). The voltmeter has an internal  resistance and therefore draws some current to measure the voltage when  placed across a resistor. This is because more current will always flow  through the path of least resistance. Therefore, the voltage drop across  the resistor will be less than the actual voltage drop due to the  voltmeter. This also results in the voltmeter showing a value lower than  the true value of the reading (Electrical Deck, 2021).
References
SCGA. (2019). Understanding Step and Touch Potential. https://www.youtube.com/watch?v=LdhP-vGaxtc 
 Links to an external site.
Electrical Deck. (2021, April 25). Sensitivity of Voltmeter and Loading Effect of Voltmeter. Electrical Deck. https://www.electricaldeck.com/2021/04/sensitivity-of-voltmeter-and-loading-effect-of-voltmeter.html#:~:text=For%20high%20resistance%20circuits%2C%20the,loading%20effect%20of%20the%20voltmeter   Links to an external site..
Engineering, E. A. E. (2019, July 28). Loading Effect of Voltmeter. Electrical and Electronics Engineering. https://electricalandelectronicsengineering.com/loading-effect-of-voltmeter/