BY4.7 Synapses

Synapses

• neurones are not in direct contact with one another
• they are separated by gaps called synapses
• the main role of the synapses is to convey action potentials between neurones

structure of a synapse

• most junctions between neurones take the role of chemical synapses
• branches of axons lie in close contact to dendrites of another neurone but don't touch
• there is a gap of 20nanometres
• impulse is transmitted by the secretion of neurotransmitters from he presynaptic membranes to diffuse into the post synaptic membrane

synaptic transmission:

• nerve impulse (action potential) arrives at the presynaptic membrane
• voltage gated calcium channels on the presynaptic membrane open
• calcium dffuses in down a concentration gradient
• vesicles fuse to the membrane and burst
• neurotransmitters (acetylcholine…