Topic 6.5:  Neurons and Synapses

Essential Idea:   Neurons transmit the message, synapses modulate the message.

At SHS, Topic 6.5 is taught in the following class unit(s):

• Learning and Memory (unit 0)
• Neural Structure and Function (unit 42)

Statements & Objectives:

6.5.U1  Neurons transmit electrical impulses.

• State the function of the nervous system.
• Draw the structure of a neuron.
• Annotate a neuron drawing with the name and function of the following cell parts:  dendrites, axon and cell body
  

6.5.U2  The myelination of nerve fibres allows for saltatory conduction.

• Outline the structure and function of myelin.
• State the role of Schwann cells in formation of myelin.
• Outline the mechanism and benefit of saltatory conduction.
• Compare the speed of nerve impulse conduction myelinated and non-myelinated neurons.​

6.5.U3  Neurons pump sodium and potassium ions across their membranes to generate a resting potential.

• Define resting potential.
• Explain three mechanisms that together create the resting potential in a neuron.
• State the voltage of the resting potential.

6.5.U4  An action potential consists of depolarization and repolarization of the neuron.

• Define action potential, depolarization and repolarization.
• Outline the mechanism of neuron depolarization.
• Outline the mechanism of neuron repolarization.

6.5.U5  Nerve impulses are action potentials propagated along the axons of neurons.

• Define nerve impulse.
• Describe how nerve impulses are propagated along the neuron axon.
• Outline the cause and consequence of the refractory period after depolarization.

6.5.U6  Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential.

• Explain how the movement of sodium ions propagates an action potential along an axon.
• Explain movement of sodium ions in a local current.
• Describe that cause of and effect of membrane potential reaching the threshold potential.

6.5.U7  Synapses are junctions between neurons and between neurons and receptors or effector cells.

• Define synapse, synaptic cleft and effector.
• State the role of neurotransmitters.​

6.5.U8  When presynaptic neurons are depolarized they release a neurotransmitter into the synapse.

• Outline the mechanism of synaptic transmission, including the role of depolarization, calcium ions, diffusion, exocytosis, neurotransmitters, receptors, sodium ions, sodium channels, threshold potential and action potential.

6.5.U9  A nerve impulse is only initiated if the threshold potential is reached.​

• Outline the role of positive feedback and sodium ions in the reaching of threshold potential.
• ​Explain why some synaptic transmissions will not lead to an action potential in a postsynaptic cell.

6.5.A1  Secretion and reabsorption of acetylcholine by neurons at synapses.

• Outline the secretion, action, reabsorption and formation of acetylcholine.

6.5.A2  Blocking of synaptic transmission at cholinergic synapses in insects by binding of neonicotinoid pesticides to acetylcholine receptors.

• Outline the mechanism of action of neonicotinoids use as insecticides.
• Define cholinergic synapse.
• Compare the proportion of cholinergic synapses in insects and humans.
• State why neonicotinoids insecticides are not highly toxic to humans.​ ​
  

6.3.S1  Analysis of oscilloscope traces showing resting potentials and action potentials.

• ​Outline the use of oscilloscopes in measuring membrane potential.
• Annotate an oscilloscope trace to show the resting potential, action potential (depolarization and repolarization), threshold potential and refractory period.

6.5.NOS  Cooperation and collaboration between groups of scientists-biologists are contributing to research into memory and learning.

• ​Describe the effects of cooperative and collaboration between groups of scientists.
• State an example of how people from multiple scientific disciplines are collaborating to understand learning and/or memory.
• Compare the growth and fixed mindsets effect on learning.
• Explain the basic biology of learning.
• Draw and explain the Ebbinghaus forgetting curve.
• Outline the impact of repetition and review on learning.
• State the impact of multitasking on memory consolidation.

In the News:

• Enzyme ensures thick insulation (2018-03-08)
  
• European agency concludes controversial ‘neonic’ pesticides threaten bees (2018-02-28)
• ​How to defeat a nerve agent (2018-01-04)
• The bitter battle over the world’s most popular insecticides (2017-11-08)
• 3D map of mouse neurons reveals complex connections (2017-10-27)
• When the brain's wiring breaks (2017-10-10)
• Controversial pesticides found in honey samples from six continents (2017-10-05)
• Newborn neurons in adult brain may help us adapt to environment (2015-02-21)
• Neuron types in brain are defined by gene activity shaping their communication patterns​ (2017-09-21)
• Why the First Drawings of Neurons Were Defaced (2017-09-28)
• ​​Optogenetics captures neuronal transmission in live mammalian brain (2014-12-25)
• How Poison Frogs Avoid Poisoning Themselves (2017-09-21)
• ​A new genetic marker for schizophrenia (2017-09-11)
• Extra gene makes mice manic (2013-10-23)
• Watching neurons talk in a living brain (2016-07-21)
• Brain's chemical signals seen in real time (2016-08-22)
• ​Neonicotinoid pesticides linked to butterfly declines in the UK (2015-12-02)
• Bedbugs develop resistance to widely used chemical treatments, rendering them ineffective (2016-01-28)
• Bee flower choices altered by exposure to pesticides (2016-03-14)
• Home And Garden Giant Ditches Class Of Pesticides That May Harm Bees​ (2016-04-16)
• Insecticide Can Cut Bee Sperm by Nearly 40 Percent, Study Finds (2016-07-28)
• Controversial insecticides linked to wild bee declines (2016-08-16)
• Minnesota Cracks Down On Neonic Pesticides, Promising Aid To Bees (2016-08-31)
• Largest-ever study of controversial pesticides finds harm to bees​ (2017-06-19)
• Ambitious neuroscience project to probe how the brain makes decisions (2017-09-19)