Sähkökalvo

Sähkökalvo, or the electric membrane, refers to the selective permeability barrier of a cell membrane that allows for the regulation of ion flow across the membrane. This phenomenon is fundamental to cellular physiology and plays a crucial role in various biological processes, including nerve impulse transmission, muscle contraction, and hormone secretion.

The cell membrane is composed of a phospholipid bilayer embedded with proteins, lipids, and carbohydrates. Among these components, ion channels and pumps are particularly important for maintaining the electrical properties of the membrane. Ion channels are protein structures that form pores allowing specific ions (such as sodium, potassium, calcium, and chloride) to pass through the membrane in response to electrical or chemical signals. In contrast, ion pumps actively transport ions against their concentration gradients, consuming energy in the form of adenosine triphosphate (ATP).

The electric membrane potential arises from the unequal distribution of ions across the membrane. In resting cells, the inside of the cell is typically negatively charged relative to the outside due to the higher concentration of negatively charged proteins and organic molecules inside the cell. This resting membrane potential is maintained by the sodium-potassium pump, which exports three sodium ions (Na+) out of the cell and imports two potassium ions (K+) for each ATP molecule hydrolyzed. The resulting imbalance in ion concentrations creates a voltage difference across the membrane, known as the membrane potential.

When stimulated, certain ion channels open, allowing ions to flow down their electrochemical gradients. For example, the influx of sodium ions during an action potential depolarizes the membrane, leading to a rapid change in membrane potential. This electrical signaling is essential for communication between cells, particularly in neurons and muscle cells. Disruptions in the function of the electric membrane can lead to various physiological disorders, including neurological and cardiovascular diseases.