2.1 - The Synapse

What is synaptic communication?

Each neuron has an all-or-none message that it passes along to the next neuron

What is an important key to remember regarding synaptic communication?

That we have many neurons working together (86 billion neurons, each with tens of thousands of connections)

True or False: Neurons can be wired together in all types of patterns

True

What is another way that complexity in neural communication arises?

The differences in neuronal firing rates

True or False: Firing rate can signal the difference between a strong and weak stimulus

True

What is another way neurons convey information?

By changing the rhythm of firing

True or False: We now know that the main method of communication between neurons is chemical

True

What is the first part in the sequence of events at the synapse during chemical transmission?

Neuron synthesizes neurotransmitters

What is the second part in the sequence of events at the synapse during chemical transmission?

Action potential travels down axon, opening voltage-gated Ca²+ channels

What is the third part in the sequence of events at the synapse during chemical transmission?

Ca²+ floods in, causing neurotransmitters to be released into synaptic cleft

What is the fourth part in the sequence of events at the synapse during chemical transmission?

Neurotransmitters bind to receptor on post-synaptic membrane which alters activity of post-synaptic cell

What is the fifth part in the sequence of events at the synapse during chemical transmission?

Neurotransmitters separate from receptors and either are inactivated or taken back up into the pre-synaptic cell

What are the two basic categories of neurotransmitters?

• Large (neuropeptides —> synthesized in soma and transported by microtubules to pre-synaptic terminal)

• Small (amino acids/monoamines/acetylcholine/synthesized in pre-synaptic terminal)

What are post-synaptic receptors?

Protein channels embedded in membrane with neurotransmitter-specific binding sites, they’re ligand-gated

True or False: Binding of neurotransmitters can have different effect depending on the type of receptor

True

How do the neurotransmitters bind to metabotropic receptor?

They binded to the exterior surfaceT

What would happen if nothing intervened the chemical transmission throughout the neurotransmitters?

They would remain active in the synapse and continue to excite or inhibit the post-synaptic cell

What are the two mechanisms terminate ongoing synaptic communication?

Inactivation and Re-uptake (more common)

What happens during inactivation in neurotransmitters?

They’re broken apart in the synapse by enzymes

What happens during re-uptake regarding neurotransmitters?

They remain active but detach from the receptor

Where are autoreceptors located?

In the pre-synaptic terminal

What do autoreceptors do?

Keep track of whether neurotransmitters have been released, and inhibit further neurotransmitter synthesis and release

What is retrograde transmission?

Where some post-synaptic cells respond to stimulation by releasing chemicals back to the pre-synaptic cell, where neurotransmitter release is inhibited

What is the main method of communication between neurons and chemical?

Electrical transmission

True or False: Electrical transmission between neurons does not exist

False, it does

What are the major classes of neurotransmitters?

Amino Acid, monamines, acetylcholine, neuropeptides, and soluble gases

True or False: Neurotransmitters can have time-limited or extended effects

True

True or False: Neurotransmitters can have spatially focused or systemic effects

True

True or False: Neurotransmitter neurons release more than one kind of neurotransmitter

True