Synaptic Transmission

•How a neuron communicates with another neuron and the effects of drugs on this process.

•Types of Neurotransmitters

Synaptic Transmission: Neuron to Neuron Communication

• Axons branch out and end near dendrites of neighboring cells

• Axon terminals are the tips of the axon’s branches

• A gap separates the axon terminals from dendrites

• Gap is the Synapse

Steps to Synaptic Transmission• Action Potential causes synaptic vesicle to open

• Neurotransmitter (NT) released into synapse

• NT fuses to receptor site in on receiving dendrite

• Receptor site opens and allows positive sodium ions to enter the dendrite triggering action potential in the next neuron.

Neurotransmitters are LikeKeys to a Lock

• Neurotransmitter molecules have specific shapes

• When NT binds to receptor, it opens & positive ions enter

• Receptor molecules have binding sites

Neurotransmitters Bonding at a Receptor Site

Drugs Impact on Synaptic Transmission

Some Drugs Work on Receptor Sites• Some Drugs are shaped extremely similar to a NT

and like a copy of a key unlock the receptor site

• Agonists: fit receptor well and mimic the NT causing Action Potential– e.g., nicotine

Some Drugs Work on Receptor Sites• Some drugs are shaped like

neurotransmitters but do NOT unlock the receptor site thus blocking it from receiving natural NT.

• Antagonists: fit the receptor but poorly and block the NT stopping the action potential message– e.g., beta blockers

Natural Neurotransmitters are like a key to a lock. They bond to the receptor site “unlocking” it

Antagonist Drugs block the receptor site. Like a key in the wrong lock, they won’t open the

door/receptor site.

Agonist drugs mimic neurotransmitters and open the receptor site

just like a copied key will unlock a door.

Addiction

How do drugs affect synaptic transmission? (5 min)