Lesson example: Chemical and neural signalling
Lesson example: Chemical and neural signalling
Theme: Interaction and interdependence
Level of organization: Cells
C2.1 Chemical signalling
C2.2 Neural signalling
Guiding questions
What interactions occur inside animal cells in response to chemical signals? (C2.1)
How can neurons interact with other cells? (C2.2)
This example presents activities that help students to unpack and conceptualize form and function. The activities can
constitute a lesson unit or be divided into smaller learning experiences. They can also be used as revision exercises or as a
task to check students’ conceptual understanding.
Synapses, cells and vesicles
Figure 1 shows a synapse from a mammalian brain. The pre-synaptic neuron has many vesicles containing
neurotransmitters.
Figure 1: Microscopy image of a synapse isolated from brain tissue
[Source: Taoufiq, Z. (2013). A high magnification image of synapse obtained by electron microscopy. Okinawa Institute of Science
and Technology Graduate University. https://www.oist.jp/news-center/photos/high-magnification-image-synapse-obtainedelectron-microscopy]
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Lesson example: Chemical and neural signalling
Figure 2 shows pancreatic acinar cells and secretory vesicles filled with hormones.
Figure 2: Microscopy image of hormone-containing secretory vesicles of pancreatic acinar cells
[Source: “OpenStax AnatPhys fig.3.12 - Pancreatic Cells Micrograph - English labels” by OpenStax and Regents of U-M Medical
School, UMich MedSchool, licence: CC BY. Source: book Anatomy and Physiology, https://openstax.org/details/books/anatomyand-physiology.]
Look at both images. What do you see? What do you wonder about these two images? How are these signalling
substances released?
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Lesson example: Chemical and neural signalling
Comparing signalling networks in fungi and mammals
The ecologist Suzanne Simard discovered that trees communicate their needs and send nutrients to each other along a
network of fungal hyphae (long, branching filamentous structures of a fungus) in the soil. Figure 3 represents a fungal
network that links a group of trees in a forest. Each circle represents a tree, and each circle’s diameter and depth of colour
represents the relative amount of nutrients that tree sends to the soil.
Figure 3: Representation of a fungal network in a forest
[Source: Beiler, K. J., Durall, D. M., Simard, S. W., Maxwell, S. A., & Kretzer, A. M. (2009). Architecture of the wood-wide web:
Rhizopogon spp. genets link multiple Douglas-fir cohorts. New Phytologist, 185, 543–553. https://doi.org/10.1111/j.14698137.2009.03069.x]
What do you see? What do you think is going on? What does it make you wonder? Now, look at Figure 4, showing brain
neurons that form functional networks and communicate via chemical and electrical synapse.
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Lesson example: Chemical and neural signalling
Figure 4: Functional networks formed by brain neurons
[Source: Rema, V., Bali, K. K., Ramachandra, R., Chugh, M., Darokhan, Z., & Chaudhary, R. (2008). Cytidine-5-diphosphocholine
supplement in early life induces stable increase in dendritic complexity of neurons in the somatosensory cortex of adult rats.
Neuroscience, 13, 155(2): 556–564. https://doi.org/10.1016/j.neuroscience.2008.04.017.]
What connections can you draw between the fungal and brain neuron networks? Do you think these two networks are
similar? If yes, why?
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Lesson example: Chemical and neural signalling
Comparing signalling networks in bacteria and humans
Cells use protein-signalling networks to detect and respond to changes in their environment. This includes information
about the presence or absence of vital nutrients as well as the presence of other cells. Bioscientists from the University of
Kansas compared bacterial protein-signalling networks with the more complex networks in eukaryotic cells. In Figure 5,
each circle represents a cell. The arrows represent the flow of proteins used in cell communication. The cells are colour coded
as “inputs” (cells that send information), “outputs” (cells that receive information) and cells that are intermediate between
inputs and outputs (cells represented by black circles).
Figure 5: Comparison of inputs and outputs of bacterial and human protein-signalling networks
[Source: Lynch, B.M. (2014). Research reveals evolution of cells’ signaling networks in diverse organisms. University of Kansas.
https://news.ku.edu/2014/04/09/research-reveals-evolution-cells-signaling-networks-diverse-organisms]
Analyse both networks. What do you see? Formulate a claim about the presented protein-signalling networks. A claim is
your interpretation of a scientific evidence. How can you support your claim? What evidence can support your claim? Raise
a question about your claim. What isn’t fully explained? What further ideas or issues does your claim raise? Record your
thinking using the table below.
My claim
Evidence supporting my claim
Question(s) about my claim
Reflect on the presented signalling networks (plants, neurons, bacterial and human signalling networks). Write down what
you used to think about this topic.
I used to think …
Do some reflection about the networks that you saw and analysed. How did they change your thinking? What is new in your
thinking about them? Write down a few ideas that emerged from your reflection.
Now, I think …
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