- Noncompetitive Ligand
- Competitive Ligand
- Endogenous Ligand 

Ligand Types 

Any substance that binds to receptors, such as neurotransmitters 

Rutgers University

Synaptic transmission is the process by which a neuron communicates with an adjacent one. It begins when an action potential reaches the axon terminal, causing neurotransmitters to be released into the synaptic cleft. These chemicals then travel across the synapse and bind to receptors on the next neuron's dendrites. If this signal is potent enough, it will trigger a new action potential, thus propagating the nerve impulse.

Synaptic Transmission

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Ligand

1) Neurons are depolarized (excited), causing an action potential to be fired which advances towards axon terminals

2) Action potential causes voltage-gated calcium channels to open 

3) Calcium ions cause synaptic vesicles to migrate to the presynaptic membrane where neurotransmitter molecules are released

4) Neurotransmitters bind to corresponding receptors on postsynaptic cells, causing a change in function of the postsynaptic cell

5) Reuptake of neurotransmitters causes neurotransmitter breakdown and any neurotransmitter action to cease

6) Presynaptic autoreceptors continue to monitor and signal increased or decreased neurotransmitter levels 


Synaptic Transmission Process 

The majority of drugs that act on the nervous system to produce changes in behavior do so by altering the complex system of synaptic transmission.
Drugs can alter: 
- Presynaptically 
- Postsynaptically

Drugs affect neural conduction and synaptic transmission

An illustration of the synaptic cleft shows neurotransmitters being released from the presynaptic axon terminal. Some of these chemical messengers bind to receptors on the postsynaptic neuron, while others are reabsorbed back into the presynaptic terminal through the process of reuptake.

Visual Representation of Synaptic Transmission

A newly developed medication is found to prolong the effects of a specific neurotransmitter. After being released, the neurotransmitter molecules remain active in the space between two neurons for much longer than usual, continuously stimulating the receiving neuron. Which part of the communication process is most likely being inhibited by this medication?

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