Question

Which of the following terms best describes a receptor located on a neuronal terminal that binds a neurotransmitter released from another neuron and decreases release of neurotransmitter from the neuronal terminal? (A) presynaptic receptor (B) heteroreceptor (C) postsynaptic receptor (D) autoreceptor (E) ionotropic receptor

Short answer

B) heteroreceptor.

Step-by-step solution

Understand the Question

The problem asks for a term that best describes a receptor on a neuron terminal that binds a neurotransmitter from another neuron, affecting the release of neurotransmitter from that terminal.

Define Key Terms

- **Presynaptic receptor**: A receptor located on the neuron that releases neurotransmitter. - **Heteroreceptor**: A receptor that responds to neurotransmitters released from another neuron. - **Postsynaptic receptor**: A receptor located on the neuron that receives the neurotransmitter. - **Autoreceptor**: A receptor located on the neuron releasing the neurotransmitter, typically responding to its own neurotransmitter. - **Ionotropic receptor**: A receptor that forms an ion channel pore.

Analyze Given Options

The definition that fits best is for a receptor that binds a neurotransmitter from another neuron and influences neurotransmitter release is a 'heteroreceptor'.

Conclusion

The term that correctly describes the situation given is 'heteroreceptor', because it specifically refers to receptors on a neuron that respond to transmitters from other neurons and influence the actions of that neuron.

Key concepts

Presynaptic Receptor

Presynaptic receptors are an important aspect of neuronal communication. They are located on the neuron that releases neurotransmitters. These receptors play an essential role in regulating neurotransmitter release by monitoring the amount of neurotransmitter available at the synaptic cleft. This regulation ensures that neurotransmitter levels remain in balance.
One key function of presynaptic receptors is to act as a feedback mechanism. They can either enhance or inhibit the release of neurotransmitters from the neuron terminal.

• Enhancing means increasing the amount of neurotransmitter released.
• Inhibiting refers to decreasing the neurotransmitter release.

The ability to modulate neurotransmitter release helps maintain synaptic efficiency and communication between neurons. This modulation is crucial for normal brain function and prevents excitotoxicity, which can cause damage when too much neurotransmitter is released.

Heteroreceptor

Heteroreceptors are specialized receptors located on a neuronal terminal. They bind with neurotransmitters released from other, adjacent neurons. This unique feature allows heteroreceptors to play a pivotal role in inter-neuronal communication and signaling.
Unlike autoreceptors, which respond to the neurotransmitter from the same neuron, heteroreceptors are sensitive to and regulate the effects of neurotransmitters from different neurons. By doing so, they influence how much neurotransmitter the neuron will release into the synaptic cleft.

• They can decrease neurotransmitter release when activated by neurotransmitters from another neuron.
• They help integrate and moderate signals received from multiple neurons.

This cross-talk between neurons helps fine-tune synaptic responses and modulate neural circuits accordingly, playing a significant part in processes such as learning and memory.

Autoreceptor

Autoreceptors are specific types of receptors located on the neuronal terminal that releases the neurotransmitter. An interesting feature of autoreceptors is that they respond specifically to the neurotransmitter released by the same neuron, not from an external source. This feedback mechanism allows the neuron to "self-regulate" its activity.
These receptors generally serve to inhibit further release of the neurotransmitter, creating a negative feedback loop. This function is crucial because it prevents the over-release of neurotransmitters that could lead to neuronal exhaustion or excitotoxicity.

• Autoreceptors modulate synaptic transmission by ensuring that neurotransmitter release is not excessive.
• They contribute to neurotransmitter homeostasis and synaptic balance.

Through this self-monitoring, neurons can maintain a stable and efficient level of communication within the nervous system.

Postsynaptic Receptor

Postsynaptic receptors are found on the neuron that receives neurotransmitters. These receptors are the primary site at which neurotransmitters exert their effects on the receiving neuron. Upon binding with neurotransmitters, postsynaptic receptors trigger a series of cellular events that either excite or inhibit the neuron.
Depending on the receptor type and the neurotransmitter involved, the effect on the postsynaptic neuron can vary:

• Excitatory signals will make the postsynaptic neuron more likely to fire an action potential.
• Inhibitory signals will make the postsynaptic neuron less likely to fire an action potential.

Postsynaptic receptors are essential for translating chemical signals into electrical ones, which is the core process of neuronal communication. They allow for the complex processing of signals that underlie mental activities such as perception, movement, and cognition.