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Lectures 8, 9 and 10
Describe a synapse
junction between two neurons allowing signals to pass from one to the other
What is synaptic transmission?
process of signalng via synapses
Where does the word synapse come from?
from Greek, ‘syn’ = together, ‘haptein’ = to fasten, join (coined by Sherrington in 1897)
How many synapses does the brain have? How does this compare to the nb of neurons?
~100 trillion (1014) synapses
~100 billion (1011) neurons so 1000 synapses per neuron
How was the disagreement over distinct neurons or a continuous net of fibres resolved?
Golgi stain (Ramón y Cajal, late 1800s)
Physiological evidence from study of reflexes (Sherrington, around 1900)
Final evidence from electron microscopy (1950s)
What’s the neuron doctrine vs the reticular theory?
existence of distinct neurons vs continuous net of fibres
How do neurons allow flexibility in complex organisms vs in very simple animals?
thanks to integration of inputs from interneurons, sensory neurons etc = output through motor neurons = behaviour // sensory input = stereotypic behaviour
What structures allow electrical synapses to function correctly and how? What are their subtypes?
gap junctions to let current pass between neurons
connexons made up of connexins
What’s the diameter of a gap junction? What flows through them?
1 - 2 nm
ions = current passing through
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