Safety

Use sanitary procedures and be aware of allergic or dietary considerations before consuming the edible representations!

Materials:

• Paper plates (one per student or team)
• Hand wipes or paper towels
• Sugar cookies (best if ordered from a grocery bakery) - these will represent the cell body
• White icing - to represent the cytoplasm
• Plastic spreaders
• Various candies for organelles (number per student):
  1 green candy - represents the nucleus
  3 banana shaped sugar candies - represents the Golgi apparatus
  3-5 chocolate covered rice bits - represents the rough endoplasmic reticulum
  3- 6 plain candy coated chocolate circles - represent mitochondria
• Pull-apart red string licorice - represents dendrites and axons
• Mini-marshmallows for myelin
• Plastic bags for students to take neuron model home (optional, but highly recommended)

Procedure

The students begin with the cell body (the cookie), putting it on a plate. Review the biochemical components of the cell membrane, recalling that the cell membrane carries an electrical charge. The cookie is then iced to represent the cytoplasm. Cytoplasm, consisting of water, ions, and sugar, has a jelly-like consistency. The organelles "float" within the cytoplasm.

The nucleus can be described as the place where the directions to make stuff for the cell resides (it is where deoxyribonucleic acid, or DNA, is located). Through DNA, genetic directions for protein synthesis are relayed to other cell organelles where the protein will be constructed. (Help the students relate to the function of DNA by recalling that in the movie "Jurassic Park", the dinosaurs are brought to life through the use of DNA found in a preserved mosquito that sucked the blood of the dinosaur.)

Over the course of a lifetime (and some neurons can be around as long as one hundred years) the neuron will need to replace worn out organelles and membrane. Proteins are made up of amino acids strung together. Some short protein chains - peptides- also act as neurotransmitters, or chemical messengers, in the nervous system. Thus, the ability to synthesize protein is extremely important in maintaining the structural integrity, and function, of the neuron. The green runt- representing the nucleus- gives the "go signal" for the cell to make proteins (thus, green = go).

Protein synthesis occurs at special sites out in the cytoplasm - special organelles, or little organs. The students then begin to construct the protein-making machinery in the cell. This includes the rough endoplasmic reticulum and the Golgi apparatus. We can explain it simply as the place where the proteins are put together and then packaged and addressed to use inside the neuron (replacing worn out parts) or outside the neuron (as a chemical messenger). Place the 3 banana shaped candies on top of one another for a convincing representation of the Golgi apparatus. If you have related history about Golgi, you can reinforce the information by asking the students who this organelle is named after. The reticulum, represented by the chocolate covered rice bits, has little bumps that represent the "stations" where the protein is made. The differences between the two types of endoplasmic reticulum (smooth and rough) and how it relates to function can be reviewed.
The last organelle placed in the cell is the mitochondria, the M & Ms. (We typically give each student a handful and allow them to choose how many to put in their neuron, as the extras invariably wind up in their mouth). Function of the mitochondria is explained with the classic label "Powerhouse of the cell". The process of oxidative respiration and the generation of ATP can be reviewed, or simply explain that oxygen is utilized here.

The students are then given 2 pieces of string licorice. They take the first and break it into 3-4 short pieces, placing the end of each into the cytoplasm (icing) at the top of the cookie (we usually explain this makes the neuron appear as though it is having a bad hair day). The other longer piece is placed at the bottom of the cookie with one end in the cytoplasm (icing) and the other extending off the plate. Definitions and explanations of each type of process are given. The analogy of a phone receiver works well. There is an earpiece to listen through (the receiving end, or dendrites) and a mouthpiece to speak into (the sending end - i.e., the axon). For more advanced students, the composition of the dendrites and axons can be elaborated, and the concept of the myelinated axon can be introduced. An insulated electrical cord works as a good visual or recall representation of specific glial cells wrapping a fatty-like substance, myelin, around the axons to keep the electrical current prorogating down the axon.

Students can make a simple circuit by connecting their axon to the dendrite of a neighboring student's cookie. Leave a gap between the axon and the dendrite, representing the synaptic space. This serves as a launch point for a discussion of the synapse, transport of chemical neurotransmitters from the cell body down the axon to the synapse, and release of chemical neurotransmitters in response to a change in electrical potential of the membrane. The impact of drugs such as cocaine on this process, and the physical changes the neuron undergoes can be introduced, explained, or researched.
Neurons consume oxygen and glucose for fuel. The more challenging the brain's task, the more fuel it consumes. (Sousa, 2001). Snacks in moderate proportions can boost neuron function and reduce lethargy and sleepiness. Carbohydrates enhance the entry of tryptophan into our brain, elevating mood (Sylwester, 2000). So eat your neuron cookie!