Synaptic Transmission
This page delves into the crucial process of synaptic transmission, which is essential for understanding how signals are passed between neurons in the nervous system.
Synaptic Transmission Process
Synaptic transmission involves several steps that allow a signal to pass from one neuron (presynaptic) to another (postsynaptic):
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Action Potential Arrival: When an action potential reaches the end of the presynaptic axon, it depolarizes the membrane.
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Calcium Influx: This depolarization opens voltage-gated calcium channels, allowing calcium ions to enter the synaptic knob.
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Vesicle Fusion: Calcium ions cause synaptic vesicles to move towards and fuse with the presynaptic membrane.
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Neurotransmitter Release: The fusion of vesicles releases neurotransmitters (such as acetylcholine) into the synaptic cleft through exocytosis.
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Diffusion and Binding: Neurotransmitters diffuse across the synaptic cleft and bind to receptor molecules on the postsynaptic membrane.
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Channel Opening: This binding causes sodium ion channels to open, allowing sodium to diffuse into the postsynaptic cell.
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Postsynaptic Potential: If enough neurotransmitter molecules bind, an action potential is generated in the postsynaptic neuron.
Highlight: The importance of synaptic transmission in A level Biology cannot be overstated, as it forms the basis for all neural communication.
Neurotransmitter Breakdown
To prevent continuous stimulation of the postsynaptic neuron, neurotransmitters are quickly broken down or removed from the synaptic cleft.
Example: In a cholinergic synapse, the enzyme acetylcholinesterase breaks down acetylcholine into acetate and choline. The choline is then recycled to produce more acetylcholine.
Vocabulary: Exocytosis is the process by which vesicles fuse with the cell membrane to release their contents outside the cell.
The detailed understanding of synaptic transmission is crucial for comprehending various neurological processes and disorders, making it a key topic in AQA A level Biology synaptic transmission exam questions.
