Synaptic Transmission

• Signals within neurons are transmitted electrically. signals between neurons are transmitted chemically across the synapse.
• Neurons communicate with each other in neural networks.
• When electrical impulses are sent down a neuron, they are called action potentials.
• when electrical impulses reach the end of a neuron (the presynaptic neuron), it triggers a release of neurotransmitters from tiny sacs called synpatic vesicles which bind to the cell membrane.
• What are neurotransmitters?

  Chemicals which diffuse across the synapse to the next neuron in the chain.
• Once a neurotransmitter crosses the gap, it is taken up by a post-synpatic receptor site on the dendrites of the next neuron.
• Acetylcholine (ACh) is found at each point where a motor neuron meets a muscle which causes the muscle to contract.
• Neurotransmitters have either excitatory or inhibitory effects on the neighbouring neuron. eg. serotonin, causes inhibition in the receiving neuron, resulting in a neuron becoming more negatively charged and less likely to fire.
• In contrast to serotonin, adrenaline causes excitation of the post-synatpic neuron by increasing its positive charge making it more likely to fire.