Types of neurotransmitter receptors | Nervous system physiology | NCLEX-RN | Khan Academy

Summary

This video explains the different types of neurotransmitter receptors and their role in neuronal communication. It clarifies that excitatory or inhibitory effects depend on the combination of neurotransmitter and receptor types at the synapse. The video introduces ionotropic receptors, which are ligand-gated ion channels affecting the cell’s potential quickly, and metabotropic receptors, which activate second messenger systems to cause slower but potentially larger and more widespread changes in cell behavior. The video emphasizes how these mechanisms contribute to the fine-tuning of neuronal signals across various synaptic locations, ultimately influencing action potential generation and neurotransmitter release.

Takeaways

• 😀 Neurons are classified as excitatory or inhibitory, but it is more accurate to describe the synapse as excitatory or inhibitory based on neurotransmitter binding and receptor interaction.
• 😀 A single neurotransmitter can bind to multiple types of receptors, and depending on the receptor, it may have excitatory or inhibitory effects on the target cell.
• 😀 Excitatory and inhibitory synapses are distributed across different parts of a neuron, including dendrites, soma, and axon terminals.
• 😀 Excitatory synapses often cause depolarization, while inhibitory synapses can prevent depolarization and block action potential initiation at the trigger zone.
• 😀 Information flow within a neuron is influenced by excitatory and inhibitory synapses located in various regions, such as dendrites, soma, and axon terminals.
• 😀 Ionotropic receptors are ligand-gated ion channels that, when activated by neurotransmitters, allow ions to pass through, leading to rapid and brief changes in the membrane potential.
• 😀 Activation of ionotropic receptors with excitatory neurotransmitters typically leads to depolarization (e.g., sodium or calcium influx), while inhibitory neurotransmitters (e.g., chloride or potassium influx) lead to hyperpolarization.
• 😀 Metabotropic receptors, unlike ionotropic receptors, do not form ion channels but instead activate second messenger systems inside the neuron, which can affect ion channels, proteins, or gene expression.
• 😀 Metabotropic receptors initiate slower, but potentially larger and more widespread effects compared to ionotropic receptors, due to the amplification processes involved in second messenger signaling.
• 😀 The activation of metabotropic receptors may cause brief or long-lasting changes in the behavior of the target cell, influencing its response to various stimuli.

Q & A

What is the main difference between excitatory and inhibitory synapses in neurons?

Excitatory and inhibitory synapses refer to how they influence the target cell's potential. Excitatory synapses cause depolarization, increasing the likelihood of an action potential, while inhibitory synapses cause hyperpolarization, reducing the chance of an action potential.

How do neurotransmitters and receptors work together in determining whether a synapse is excitatory or inhibitory?

The neurotransmitter released at the synapse binds to specific receptors on the post-synaptic membrane. Depending on the type of receptor, the neurotransmitter can either excite or inhibit the target cell. The same neurotransmitter can be excitatory or inhibitory, depending on which receptor it binds to.

What role do dendrites play in receiving excitatory input?

Dendrites are often the site where excitatory synapses are located. These synapses release neurotransmitters that cause depolarization, spreading electrical signals down the dendrites and toward the soma of the neuron.

How do inhibitory synapses affect the soma of a neuron?

Inhibitory synapses on the soma prevent depolarizations from reaching the trigger zone of the neuron. This helps block the initiation of action potentials, thereby reducing the likelihood of the neuron firing.

What is the function of synapses located on axon terminals?

Synapses on axon terminals can either enhance or reduce the amount of neurotransmitter released when an action potential arrives at the axon terminal. These synapses help fine-tune the output of the neuron.

What are ionotropic receptors, and how do they function?

Ionotropic receptors are ligand-gated ion channels. When a neurotransmitter binds to them, they open and allow specific ions (such as sodium or chloride) to flow into or out of the neuron, leading to a rapid and localized change in the membrane potential.

What is the difference between ionotropic and metabotropic receptors?

Ionotropic receptors are fast and directly influence ion flow, causing rapid changes in the membrane potential. In contrast, metabotropic receptors activate second messenger systems inside the neuron, which can lead to slower, more widespread, and potentially longer-lasting effects.

What happens when ionotropic receptors allow sodium or calcium ions to enter the neuron?

When sodium or calcium ions enter the neuron through ionotropic receptors, the neuron is depolarized, making the inside of the neuron more positive. This increases the likelihood of generating an action potential.

How do chloride and potassium ions contribute to inhibitory effects in ionotropic receptors?

When chloride ions flow into the neuron or potassium ions flow out, they carry negative charges or reduce positive charges, making the inside of the neuron more negative and leading to inhibition or hyperpolarization of the neuron.

What is the role of second messenger systems in metabotropic receptor activation?

Second messenger systems activated by metabotropic receptors can affect ion channels, proteins, or even gene expression. These effects are slower but can lead to more extensive changes in the behavior of the neuron, either by causing brief excitations or inhibitions or by inducing longer-term modifications in the cell's functions.