Chapter 12 - Section 12.5 - Synapses - Before You Go On - Page 461: 21

Neuromodulators are signaling molecules in the nervous system that play a distinct role from neurotransmitters. While neurotransmitters are primarily responsible for transmitting rapid and specific signals at synapses, neuromodulators serve broader regulatory functions to modulate the overall activity of neural circuits. Here's a comparison and contrast between neuromodulators and neurotransmitters: **Function:** - **Neurotransmitters:** - Neurotransmitters are involved in fast, point-to-point communication between neurons or from neurons to target cells (e.g., muscle cells or glands). - They transmit specific and rapid signals that result in postsynaptic membrane potential changes, leading to immediate and localized responses. - Neurotransmitters have well-defined roles in mediating excitatory or inhibitory effects on postsynaptic neurons. - **Neuromodulators:** - Neuromodulators have a more diffuse and modulatory role in the nervous system. - They do not cause immediate postsynaptic responses but instead alter the responsiveness of neural circuits and synapses. - Neuromodulators can affect multiple neurons or synapses simultaneously and have longer-lasting effects than neurotransmitters. **Timing:** - **Neurotransmitters:** - Neurotransmitter release and action occur rapidly and are typically associated with synaptic transmission. - The effects of neurotransmitters are short-lived, as they are rapidly removed or terminated after binding to receptors. - **Neuromodulators:** - Neuromodulator effects are slower and more prolonged compared to neurotransmitters. - They can influence neural circuitry over extended periods, leading to changes in synaptic strength, plasticity, and overall network activity. **Localization:** - **Neurotransmitters:** - Neurotransmitters act locally at synapses and have specific receptors on postsynaptic neurons or target cells. - Their actions are confined to the immediate synaptic region. - **Neuromodulators:** - Neuromodulators can act globally, affecting multiple neurons and synapses within a neural network. - They may diffuse more extensively within the nervous system and influence a broader range of neurons. **Examples:** - **Neurotransmitters:** - Examples of neurotransmitters include glutamate (excitatory), gamma-aminobutyric acid (GABA) (inhibitory), and acetylcholine (both excitatory and inhibitory), among others. - **Neuromodulators:** - Neuromodulators include substances like serotonin, dopamine, norepinephrine, and neuropeptides (e.g., endorphins and substance P). In summary, neurotransmitters are specialized for rapid and specific synaptic transmission, whereas neuromodulators have a broader and more prolonged influence on neural circuits and synaptic plasticity. While neurotransmitters transmit specific information, neuromodulators help regulate the overall state and function of neural networks, playing a critical role in processes like learning, memory, mood, and arousal.

Neuromodulators are signaling molecules in the nervous system that play a distinct role from neurotransmitters. While neurotransmitters are primarily responsible for transmitting rapid and specific signals at synapses, neuromodulators serve broader regulatory functions to modulate the overall activity of neural circuits. Here's a comparison and contrast between neuromodulators and neurotransmitters: **Function:** - **Neurotransmitters:** - Neurotransmitters are involved in fast, point-to-point communication between neurons or from neurons to target cells (e.g., muscle cells or glands). - They transmit specific and rapid signals that result in postsynaptic membrane potential changes, leading to immediate and localized responses. - Neurotransmitters have well-defined roles in mediating excitatory or inhibitory effects on postsynaptic neurons. - **Neuromodulators:** - Neuromodulators have a more diffuse and modulatory role in the nervous system. - They do not cause immediate postsynaptic responses but instead alter the responsiveness of neural circuits and synapses. - Neuromodulators can affect multiple neurons or synapses simultaneously and have longer-lasting effects than neurotransmitters. **Timing:** - **Neurotransmitters:** - Neurotransmitter release and action occur rapidly and are typically associated with synaptic transmission. - The effects of neurotransmitters are short-lived, as they are rapidly removed or terminated after binding to receptors. - **Neuromodulators:** - Neuromodulator effects are slower and more prolonged compared to neurotransmitters. - They can influence neural circuitry over extended periods, leading to changes in synaptic strength, plasticity, and overall network activity. **Localization:** - **Neurotransmitters:** - Neurotransmitters act locally at synapses and have specific receptors on postsynaptic neurons or target cells. - Their actions are confined to the immediate synaptic region. - **Neuromodulators:** - Neuromodulators can act globally, affecting multiple neurons and synapses within a neural network. - They may diffuse more extensively within the nervous system and influence a broader range of neurons. **Examples:** - **Neurotransmitters:** - Examples of neurotransmitters include glutamate (excitatory), gamma-aminobutyric acid (GABA) (inhibitory), and acetylcholine (both excitatory and inhibitory), among others. - **Neuromodulators:** - Neuromodulators include substances like serotonin, dopamine, norepinephrine, and neuropeptides (e.g., endorphins and substance P). In summary, neurotransmitters are specialized for rapid and specific synaptic transmission, whereas neuromodulators have a broader and more prolonged influence on neural circuits and synaptic plasticity. While neurotransmitters transmit specific information, neuromodulators help regulate the overall state and function of neural networks, playing a critical role in processes like learning, memory, mood, and arousal.