Essential Idea
Neurons transmit the message, synapses modulate the message.
Understandings
Neurons transmit electrical impulses.
The myelination of nerve fibres allows for saltatory conduction.
Neurons pump sodium and potassium ions across their membranes to generate a resting potential.
An action potential consists of depolarization and repolarization of the neuron.
Nerve impulses are action potentials propagated along the axons of neurons.
Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential.
Synapses are junctions between neurons and between neurons and receptor or effector cells.
When presynaptic neurons are depolarized they release a neurotransmitter into the synapse.
A nerve impulse is only initiated if the threshold potential is reached.
Applications
Secretion and reabsorption of acetylcholine by neurons at synapses.
Blocking of synaptic transmission at cholinergic synapses in insects by binding of neonicotinoid pesticides to acetylcholine receptors. **Video by Kurzgesagt (6:19)**
Skills
Analysis of oscilloscope traces showing resting potentials and action potentials.
Guidance
The details of structure of different types of neuron are NOT needed.
Only chemical synapses are required, not electrical, and they can simply be referred to as synapses.
Key Vocabulary
Neuron
Presynaptic & postsynaptic
Electrical impulse
Axon
Myelination
Saltatory conduction
Resting potential
Sodium/Potassium pump
Threshold potential
Action potential
Depolarization
Repolarization
Hyperpolarization
Synapse
Neurotransmittor
Acetylcholine
Secretion
Reabsorption
Neonicotinoid pesticides
Target cells
Receptor cell
Effector cell
Oscilloscope tracing
Textbook Reading and/or Activities
Click HERE for a pdf of chapter 6.
Pages 314-323
Challenge Yourself (p.320)
Exercises (p.323)
Notes
i-Biology Notes (Slides 1-23)
A detailed set of notes, prepared by Stephen Taylor, examining U1 - U8 and A2 - A3.
i-Biology Study Questions (Not available)
A series of questions, prepared by Stephen Taylor, to help check your understanding of the IB learning expectations. This is VERY GOOD practice.
A detailed set of notes, prepared by Chris Paine, examining all of the IB learning expectations.
A series of questions, prepared by Chris Paine, to help check your understanding of the IB learning expectations. This is VERY GOOD practice.
Learning Activities
Title
Description
Supplemental Reading
Neonicotinoids > How they work
This short read (<5 mins), prepared by Pesticide Action Network UK, outlines the process by which neonicotinoids block receptors within insects leading to death.
Neonicotinoids: new warning on pesticide harm to bees
This short article (5-10 mins), published by The Guardian on Oct.28, 2015, outlines the potential risks of using neonictinoid pesticides.
This video outlines the process by which neurons reach action potential and transmit electrical impulses along their length.
This short video outlines the process by which neurotransmitters conduct chemical messages from one neuron to the next.
Should Watch Videos
This video outlines the process by which an electrical signal is transmitted through a neuron via repeated action potentials.
This short video will help you better understand the better animations in both the previous and following videos.
This video outlines the process by which an action potential is generated within a neuron.
Must Watch Videos
This video outlines the structure of a neuron and the process by which signals are transmitted along its length and from one to the next as messages are sent throughout the body.