AQA Psychology Biopsychology The Synapse. Video No. 9

Summary

This video explores synaptic transmission, the process by which neurons communicate across synapses. When an action potential reaches the axon terminal, neurotransmitters are released into the synaptic cleft, where they bind to receptor sites on the postsynaptic neuron, influencing its activity. Synapses can be excitatory or inhibitory, determining whether the postsynaptic neuron fires more or less frequently. The balance between these inputs, a process known as summation, ultimately determines the neuron's firing rate. The video also discusses the roles of neurotransmitters like serotonin and dopamine, and how drugs can alter synaptic activity.

Takeaways

• 😀 Neurons communicate through action potentials that travel along their axons to transmit information across the body.
• 😀 The synapse is the tiny gap between the axon terminal of one neuron and the dendrite of another where information transfer occurs.
• 😀 Action potentials cannot travel across the synapse; instead, neurotransmitters are used to transfer the signal chemically across the synaptic cleft.
• 😀 Neurotransmitters diffuse across the synaptic cleft due to their natural motion, a process known as diffusion, and can travel quickly (up to 200 times per second).
• 😀 The presynaptic neuron releases neurotransmitters into the synapse through exocytosis, where vesicles containing neurotransmitters fuse with the presynaptic membrane.
• 😀 When neurotransmitters bind to receptor sites on the postsynaptic neuron, they activate it, allowing the signal to be transferred from one neuron to the next.
• 😀 Excitatory synapses lead to a high rate of firing in the postsynaptic neuron when the presynaptic neuron fires rapidly, promoting signal transmission.
• 😀 Inhibitory synapses reduce the firing rate of the postsynaptic neuron when the presynaptic neuron fires rapidly, limiting the signal transmission.
• 😀 Summation is the process by which a nerve cell’s activity is determined by the balance of excitatory and inhibitory inputs it receives.
• 😀 Drugs can affect synaptic transmission by blocking neurotransmitter receptors or by increasing the amount of neurotransmitters available in the synapse.
• 😀 Each neuron can receive multiple excitatory and inhibitory signals from many synapses, influencing its overall activity and behavior.

Q & A

What is the main topic of the video?

The main topic of the video is synaptic transmission, including the role of neurotransmitters, the process of excitation and inhibition, and how information is transferred between nerve cells across synapses.

What is the synaptic cleft?

The synaptic cleft, also known as the synaptic gap, is the small space between the axon terminal of one neuron and the dendrite of the next neuron, across which neurotransmitters travel to facilitate communication.

How do neurotransmitters cross the synaptic cleft?

Neurotransmitters cross the synaptic cleft by diffusion. They are released from vesicles in the presynaptic neuron and move across the gap to bind with receptor sites on the postsynaptic neuron.

What is exocytosis in the context of synaptic transmission?

Exocytosis is the process where vesicles containing neurotransmitters fuse with the presynaptic membrane, releasing their contents into the synaptic cleft.

What role does the electron microscope play in studying synapses?

The electron microscope allows for the observation of synapses, which are too small to be seen with conventional optical microscopes. This was crucial in the 1950s for the development of our understanding of synaptic structure.

What are presynaptic and postsynaptic neurons?

The presynaptic neuron is the neuron that sends information into the synapse, while the postsynaptic neuron is the one that receives information from the synapse.

What is the relationship between presynaptic and postsynaptic neuron activity in an excitatory synapse?

In an excitatory synapse, a high firing rate in the presynaptic neuron leads to a high firing rate in the postsynaptic neuron, creating a positive relationship between the two.

How do inhibitory synapses differ from excitatory synapses?

In inhibitory synapses, a high firing rate in the presynaptic neuron leads to a lower firing rate in the postsynaptic neuron, creating an inverse relationship between their activities.

What is the role of summation in neuronal activity?

Summation is the process by which a nerve cell's activity is determined by the combined influence of all excitatory and inhibitory inputs. It decides whether the neuron will fire an action potential based on the balance of these inputs.

What is the difference between excitatory and inhibitory neurotransmitters?

Excitatory neurotransmitters, like dopamine, increase the likelihood of the postsynaptic neuron firing, whereas inhibitory neurotransmitters, like serotonin, decrease this likelihood, thereby reducing the postsynaptic neuron's firing rate.