Excitatory synapse

Definition

An excitatory synapse is a type of synaptic connection where the neurotransmitter released from the presynaptic neuron increases the likelihood of an action potential occurring in the postsynaptic neuron. This process typically involves the binding of neurotransmitters to specific receptors, leading to the opening of ion channels that allow positively charged ions, like sodium (Na+), to flow into the postsynaptic cell. The net effect is a depolarization of the postsynaptic membrane, moving it closer to the threshold for firing an action potential.

5 Must Know Facts For Your Next Test

1. Excitatory synapses primarily use neurotransmitters such as glutamate, which bind to receptors and facilitate ion channel opening.
2. The result of an excitatory synapse is often an excitatory postsynaptic potential (EPSP), which represents a small depolarization.
3. If the cumulative effect of EPSPs at a postsynaptic neuron reaches the threshold potential, it can trigger an action potential.
4. Excitatory synapses play a crucial role in processes like learning and memory by strengthening synaptic connections during repetitive activity.
5. Dysfunction in excitatory synapses has been linked to various neurological disorders, including epilepsy and schizophrenia.

Review Questions

• How does an excitatory synapse contribute to the generation of an action potential in a postsynaptic neuron?
  • An excitatory synapse increases the chances of an action potential in the postsynaptic neuron by releasing neurotransmitters that bind to receptors on the postsynaptic membrane. This binding opens ion channels, allowing positively charged ions like sodium to flow in, which causes depolarization. If this depolarization is strong enough to reach the threshold, an action potential will be generated in the neuron.
• Compare and contrast excitatory and inhibitory synapses in terms of their functions and mechanisms.
  • Excitatory synapses enhance neuronal activity by increasing the likelihood of action potentials, primarily through the influx of sodium ions. In contrast, inhibitory synapses decrease neuronal firing by allowing negatively charged ions like chloride to enter or positively charged ions to exit. While excitatory synapses generate excitatory postsynaptic potentials (EPSPs) leading to depolarization, inhibitory synapses produce inhibitory postsynaptic potentials (IPSPs) that hyperpolarize the membrane.
• Evaluate the implications of dysfunction in excitatory synapses on brain health and behavior.
  • Dysfunction in excitatory synapses can lead to significant brain health issues and behavioral changes. For instance, excessive excitatory signaling can contribute to conditions like epilepsy, characterized by uncontrollable neural activity. Conversely, insufficient excitation may be involved in disorders such as depression or schizophrenia, where cognitive functions are impaired. Understanding these implications is crucial for developing targeted treatments for neurological and psychiatric conditions.

Related terms

Inhibitory Synapse: A type of synapse where neurotransmitter release decreases the likelihood of an action potential in the postsynaptic neuron, often by allowing negatively charged ions to enter.

Neurotransmitter: Chemicals released by neurons that transmit signals across a synapse to communicate with other neurons or target cells.

Action Potential:

A rapid electrical signal that travels along the axon of a neuron, triggered when the membrane potential reaches a certain threshold.