Second messengers

Definition

Second messengers are intracellular signaling molecules that relay signals received at cell surface receptors to target molecules within the cell, facilitating a cascade of cellular responses. They play a crucial role in transmitting signals from neurotransmitters that bind to receptors on the postsynaptic neuron, effectively translating external chemical signals into appropriate cellular actions, such as changes in gene expression or enzyme activity.

5 Must Know Facts For Your Next Test

1. Second messengers can amplify the strength of the signal received from neurotransmitters, allowing for a more significant physiological response from the target cell.
2. Common examples of second messengers include cAMP, cGMP, inositol trisphosphate (IP3), and calcium ions (Ca2+).
3. The action of second messengers is often rapid, allowing cells to respond quickly to changes in their environment.
4. Different types of receptors can activate different second messenger pathways, resulting in diverse cellular responses even when the same neurotransmitter is involved.
5. Dysfunction in second messenger systems has been implicated in various neurological disorders, highlighting their importance in maintaining normal brain function.

Review Questions

• How do second messengers contribute to the process of synaptic transmission?
  • Second messengers are integral to synaptic transmission as they relay and amplify the signals generated when neurotransmitters bind to receptors on the postsynaptic neuron. When a neurotransmitter activates a receptor, it can lead to the activation of second messengers like cAMP or calcium ions. These second messengers then propagate the signal within the neuron, ultimately resulting in various cellular responses such as changes in ion conductance or gene expression.
• Discuss the differences between first messengers and second messengers in the context of neurotransmission.
  • First messengers refer to the external signaling molecules, typically neurotransmitters, that bind to receptors on the cell surface and initiate the signaling process. In contrast, second messengers are generated within the cell as a result of receptor activation by first messengers. While first messengers initiate the signaling cascade, second messengers play a pivotal role in amplifying and transmitting that signal inside the cell, leading to specific physiological effects.
• Evaluate the significance of second messenger pathways in understanding neurological disorders and potential therapies.
  • Second messenger pathways are crucial for understanding neurological disorders because disruptions in these signaling systems can lead to abnormal cellular functions associated with conditions like depression, schizophrenia, or neurodegenerative diseases. By studying these pathways, researchers can identify potential therapeutic targets for drug development that aim to restore normal signaling. For example, medications that modulate specific second messenger systems may improve synaptic function and alleviate symptoms related to these disorders.

Related terms

Neurotransmitter: Chemicals released by neurons that transmit signals across a synapse to another neuron or target cell.

G-protein coupled receptors (GPCRs): A large family of cell surface receptors that, when activated by ligands like neurotransmitters, initiate a signaling cascade involving second messengers.

cAMP (cyclic adenosine monophosphate): A common second messenger that is produced from ATP and plays a vital role in mediating various cellular processes in response to hormonal signals.