6.5 Neurons and Synapses
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
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
When presynaptic neurons are depolarized they release a neurotransmitter into the
A nerve impulse is only initiated if the threshold potential is reached.
Applications and Skills:
● Application: Secretion and reabsorption of acetylcholine by neurons at synapses.
● Application: Blocking of synaptic transmission at cholinergic synapses in insects by
binding of neonicotinoid pesticides to acetylcholine receptors.
● Skill: Analysis of oscilloscope traces showing resting
potentials and action potentials.
What are the names of the two systems that control our
What are the two main parts of the nervous system?
What makes up the central nervous system?
Label the CNS, brain, spinal cord and peripheral nerves on the
Complete the table:
Y or N
Draw and label a motor neuron in the space below.
Go to http://sites.sinauer.com/neuroscience5e/animations02.01.html
Put the sentences in order to explain how a resting potential is achieved:
This requires ATP
Sodium and potassium cation pumps transport Na+ out and K+ in
Concentration of Na+ is high outside the neuron
This results in the inside being more negative than the outside
Concentration of K+ is high inside the neuron
Membrane is more permeable to K+ than Na+
Difference in concentration of ions maintained by active transport against
Concentration of K+ inside neuron 20x greater than outside so K+ ions rapidly diffuse
out until equilibrium reached
How do neurons transmit a nervous impulse?
Watch the Action Potential animations:
____________________ can reverse the charge on a neuron (-70 to +40 mV). The membrane
becomes _______________________. If the stimulus exceeds a certain
value an _______________________________ results.
Label the graph showing the changes in potential difference across the nerve as a nervous
impulse is transmitted. Words to use: Depolarisation, repolarisation, resting potential,
Watch theanimation: http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter14/animation__transmission_across_a_synap
Why do we need synapses?
Label this diagram of a synapse:
Include these labels - pre-synaptic neuron, post-synaptic neuron, mitochondria, vesicle,
neurotransmitter, synaptic cleft, calcium ions, voltage gated calcium channels, action
potential, sodium channel,
Identify what is happening at each
Past Paper Questions
2. Draw and label a diagram of a motor neuron showing the direction of nerve impulse
3. Explain how a nerve impulse passes along a non-myelinated neuron (8)
4. Explain the principles of synaptic transmission (8)
5. Outline the use of four method of membrane transport in nerves and synapses (8)