Hyperpolarisoitua

Hyperpolarisoitua is a Finnish-language verb meaning to become hyperpolarized. In neuroscience, hyperpolarization refers to a change in a cell’s membrane potential toward more negative values than the resting potential. This state reduces the likelihood that the cell will fire an action potential and thus decreases neuronal excitability.

Hyperpolarization can arise from multiple mechanisms. It often results from the efflux of potassium through various potassium channels or the influx of chloride via inhibitory receptors such as GABA_A or glycine receptors. It can occur passively through leak channels or actively as part of inhibitory postsynaptic potentials. In some cells, ions are redistributed by pumps that further stabilize or enhance the hyperpolarized state.

Functional significance of hyperpolarization includes shaping the timing and probability of neuronal firing, enabling inhibitory control within neural circuits, and contributing to rebound phenomena when channels recover from inactivation after an action potential. The transient hyperpolarization that follows an action potential, known as afterhyperpolarization, is a common example of this process and helps regulate firing rates. Hyperpolarization also modulates rhythmic activity in various tissues, including cardiac and smooth muscle cells, by affecting excitability and response to stimuli.

Measurement and terminology are typical in millivolts relative to the resting membrane potential. The term hyperpolarisoitua is primarily used in Finnish-language texts to describe the process or state of becoming hyperpolarized, and is linked to the broader concept of hyperpolarization in cellular physiology.