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Excitability is a fundamental property of living cells, particularly neurons, that refers to their ability to generate electrical signals in response to stimuli. This property is crucial for the transmission of information within the nervous system. Excitability is typically measured by the threshold voltage required to initiate an action potential, the smallest electrical signal that can trigger a neuron to fire.

The excitability of a neuron can be influenced by various factors, including the concentration of neurotransmitters, the presence of ion channels, and the cell's membrane potential. For example, an increase in the concentration of excitatory neurotransmitters like glutamate can lower the threshold voltage, making the neuron more excitable. Conversely, inhibitory neurotransmitters like GABA can increase the threshold voltage, making the neuron less excitable.

Excitability is not a static property but can change dynamically in response to environmental and internal cues. This plasticity is essential for learning and memory, as it allows neurons to adjust their responsiveness based on past experiences. For instance, long-term potentiation (LTP) and long-term depression (LTD) are forms of synaptic plasticity that enhance or weaken the strength of connections between neurons, respectively, by altering the excitability of the postsynaptic neuron.

The study of excitability is a key area in neuroscience, as it provides insights into the mechanisms underlying brain function and dysfunction. Understanding excitability can help in the development of treatments for neurological disorders, such as epilepsy and depression, where abnormal excitability plays a significant role.