Overview
This lecture explains how neurons communicate through synaptic transmission, focusing on the roles of neurotransmitters, synaptic structure, and signal clearance mechanisms.
Synapse Structure and Function
- A synapse is where two neurons exchange chemical signals without direct contact.
- The synaptic cleft is a tiny gap (less than 40 nm wide) between the two neurons.
- The presynaptic neuron sends the signal, while the postsynaptic neuron receives it.
Neurotransmitters and Vesicles
- Neurotransmitters are chemical messengers stored in vesicles within the presynaptic neuron.
- Each vesicle holds thousands of neurotransmitter molecules.
Signal Transmission Process
- An action potential (electrical signal) in the presynaptic neuron triggers vesicles to release neurotransmitters into the synaptic cleft.
- Neurotransmitters cross the synaptic cleft and bind to receptors on the postsynaptic membrane.
- Binding can increase or decrease the likelihood that the postsynaptic neuron will fire its own action potential.
Clearing the Synaptic Cleft
- Neurotransmitters in the synaptic cleft are removed by diffusion, reuptake, or enzymatic breakdown.
- Reuptake is when neurotransmitters are absorbed back into the presynaptic neuron to be recycled.
- Enzymatic breakdown involves enzymes degrading neurotransmitters, with parts reused to make new neurotransmitters.
Key Terms & Definitions
- Synapse — Junction where two neurons exchange signals.
- Synaptic cleft — Tiny gap between two neurons at a synapse.
- Presynaptic neuron — Neuron sending the signal.
- Postsynaptic neuron — Neuron receiving the signal.
- Neurotransmitter — Chemical messenger transmitting signals across a synapse.
- Vesicle — Small sac storing neurotransmitters.
- Action potential — Electrical signal triggering neurotransmitter release.
- Reuptake — Absorption of neurotransmitters back into the presynaptic neuron.
- Enzymatic breakdown — Enzymes breaking down neurotransmitters in the synaptic cleft.
Action Items / Next Steps
- Review the process of synaptic transmission and mechanisms for neurotransmitter clearance.