Neurotransmitters

Definition

Neurotransmitters are chemical messengers that transmit signals across synapses from one neuron to another, playing a vital role in the communication within the nervous system. They are released by neurons in response to an action potential and bind to specific receptors on the target neuron, leading to a variety of physiological responses. Understanding neurotransmitters is essential for comprehending how signal transduction pathways and second messengers facilitate cellular responses to external stimuli.

5 Must Know Facts For Your Next Test

1. There are several major types of neurotransmitters, including excitatory neurotransmitters like glutamate, which promote action potentials, and inhibitory neurotransmitters like gamma-aminobutyric acid (GABA), which prevent them.
2. Neurotransmitters can have diverse effects on target cells, influencing functions such as mood, memory, and muscle contraction.
3. The release of neurotransmitters is often regulated by calcium ions, which enter the neuron during an action potential and trigger vesicles containing neurotransmitters to fuse with the membrane.
4. Some common neurotransmitters include dopamine, serotonin, norepinephrine, and acetylcholine, each associated with specific physiological functions and behaviors.
5. Disruptions in neurotransmitter signaling can lead to various neurological disorders, including depression, anxiety, schizophrenia, and Parkinson's disease.

Review Questions

• How do neurotransmitters facilitate communication between neurons at the synapse?
  • Neurotransmitters facilitate communication by being released from the presynaptic neuron into the synaptic cleft upon an action potential. They then bind to specific receptors on the postsynaptic neuron, leading to either excitatory or inhibitory signals. This binding initiates a series of events that may involve second messengers, ultimately influencing the likelihood of the postsynaptic neuron firing an action potential.
• What is the role of second messengers in the signaling pathways initiated by neurotransmitter binding?
  • Second messengers play a crucial role in amplifying and propagating the signal initiated by neurotransmitter binding to its receptor. Once a neurotransmitter binds to a receptor on the postsynaptic neuron, it can activate intracellular signaling pathways that produce second messengers like cyclic AMP or calcium ions. These molecules further transmit the signal within the cell, leading to various physiological responses such as changes in gene expression or neuronal excitability.
• Evaluate how imbalances in specific neurotransmitters can lead to neurological disorders and their implications for treatment strategies.
  • Imbalances in neurotransmitter levels can lead to a range of neurological disorders; for example, low levels of serotonin are often linked to depression, while dopamine deficiencies are associated with Parkinson's disease. Understanding these connections allows researchers and clinicians to develop targeted treatment strategies aimed at restoring normal neurotransmitter function. This could involve pharmacological interventions that enhance or inhibit specific neurotransmitter activity or therapies that aim to modify receptor sensitivity or second messenger systems.

Related terms

Synapse: The junction between two neurons where neurotransmitters are released and received, enabling communication between cells.

Receptor:

A protein molecule on the surface of a cell that binds to specific neurotransmitters, triggering a response within the cell.

Second Messenger: Intracellular signaling molecules that are activated by receptors upon neurotransmitter binding, amplifying the signal and mediating various cellular responses.