Question

Name four properties that you would expect a chemical substance to possess if it functions as a neurotransmitter at a synapse you are investigating.

Short answer

Answer: The four essential properties are: 1) synthesis and storage within neurons, 2) release from the presynaptic neuron, 3) binding to specific receptors on the postsynaptic neuron, and 4) inactivation and removal from the synaptic cleft.

Step-by-step solution

1. Define a Neurotransmitter

A neurotransmitter is a chemical substance that plays a fundamental role in the communication between neurons in the nervous system. These molecules enable the transmission of electrical signals across synapses, which are the small gaps separating adjacent neurons. Neurotransmitters are released by the presynaptic neuron, cross the synaptic cleft, and bind to receptors on the postsynaptic neuron, thereby relaying the message and allowing the signal to continue on its path.

2. Property 1: Synthesis and Storage

A chemical substance must be synthesized within neurons in order to function as a neurotransmitter. The substance should also be stored in synaptic vesicles within the presynaptic neuron prior to its release. This storage allows for the efficient and controlled release of neurotransmitters when needed for neural communication.

3. Property 2: Release from Presynaptic Neuron

For a chemical substance to act as a neurotransmitter, it must be released from the presynaptic neuron into the synaptic cleft in response to a neuronal signal. This often occurs when an action potential reaches the end of the presynaptic neuron, causing the voltage-gated calcium channels to open and allow calcium ions to flow into the cell. This influx of calcium prompts the fusion of synaptic vesicles with the presynaptic membrane, resulting in the release of the neurotransmitter into the synaptic cleft.

4. Property 3: Postsynaptic Receptor Binding

The chemical substance must have specific receptors on the postsynaptic neuron to which it can bind and generate a response. This binding facilitates signal transmission across the synapse, as the receptor activation on the postsynaptic neuron leads to the opening or closing of ion channels, which in turn causes changes in the membrane potential. Consequently, this could either trigger an excitatory or inhibitory response in the postsynaptic cell.

5. Property 4: Inactivation and Removal

Finally, neurotransmitters must be rapidly inactivated and removed from the synaptic cleft in order to prevent persistent signaling and allow for subsequent synaptic transmission. This can be achieved through several mechanisms, including reuptake by the presynaptic neuron, enzymatic degradation of the neurotransmitter, or diffusion away from the synapse. An efficient inactivation and elimination process is essential for maintaining effective neural communication and preventing signal overload.