Permeability is the permeability of inorganic or organic solids to a so-called permeate. This permeate can correspond to gases, liquids, or other molecules and is relevant in the body, for example, to cell membranes and blood vessels. In psychology, on the other hand, permeability is receptivity to subconscious impulses.
What is permeability?
Biological membranes are permeable to different substances, such as different gases or liquids. This permeability corresponds to membrane permeability. Biological membranes are permeable to different substances, such as different gases or liquids. This permeability corresponds to the membrane permeability. However, permeability does not only concern cell membranes, but can also refer to other organic and inorganic substances. In relation to the blood vessels of an organism, for example, permeability can correspond to the vascular permeability for solid blood components, such as the permeability for immune cells or clotting factors. In connection with capillaries, this is also referred to as capillary permeability. A special form of permeability is also semipermeability or selective permeability. A semipermeable substance is permeable only for certain molecules. For others, meanwhile, there is no permeability. Semipermeability is often based on a size-based selection of molecules. In the case of membranes, for example, often only molecules up to a certain particle size enter the interior of the cell. Psychology, on the other hand, defines permeability as a receptivity to subconscious impulses. In social psychology, moreover, the term may refer to the ease with which people move between classes and strata.
Function and task
Organic and inorganic substances are either impermeable, that is, impermeable, or have a certain permeability. This permeability is based on driving forces such as the concentration and pressure gradients and allows the substance to be permeated by other substances such as gases or liquids. For the membranes of cells, permeability is a vital property for mass transfer. The substance that passes through is also called permeate. Due to external influences, a permeate moves towards lower concentrations, i.e. towards the lower partial pressure. This process of permeation consists of various substeps. First, so-called sorption takes place at the interface of the solid. Vapors, gases or the chemicals of a solution as well as suspended substances are thus absorbed by the solid surface. Then the permeate diffuses through the solid. During this diffusion, the permeate penetrates the pores or molecular interstices of the solid material. Desorption then takes place, during which a so-called adsorbate leaves the solid in gaseous form on the other side. If the solid in question is a membrane, its interface can also be semipermeable or partially permeable. Semipermeable membranes, for example, allow solvents to pass through, but not the substances dissolved in them. This means that only molecules up to a certain molar mass can pass through. This semipermeability is the basis of osmosis of all cells, i.e. for the flow of molecular particles through a cell membrane. In relation to vessels, the term permeability can refer to the permeability of blood to solids. Vascular permeability plays a role primarily for blood capillaries and venules and depends on the endothelium of the vessels. Capillary permeability also allows selective exchange of substances between intravascular space and the interior of the vessels. Lipid-soluble and small substances, such as carbon dioxide and oxygen, can easily pass through the endothelium. Capillary permeability is thus involved in gas exchange. In contrast, large-molecule substances, such as proteins, and immobile cells, such as erythrocytes, do not diffuse through the walls of the capillaries.
Diseases and disorders
Directly related to vascular permeability are systemic inflammatory responses such as sepsis. In sepsis, vascular permeability increases. The cause of sepsis is usually trauma, major surgery, burns, or infection. Germs enter the bloodstream in sepsis and cause blood poisoning in the sense of a global inflammatory reaction.Increased vascular permeability also characterizes allergic reactions of the first type and can lead to the formation of edema. Normally, an increase in vascular permeability is preceded by the release of mediator substances such as histamine. As a result of the increase, fluid leaks from the vessels, often causing the tissues to swell. Permeability disorders can also relate to membrane permeability. Membrane permeability disorders in many cases precede cardiovascular disease. The consequence is often a disturbance of the electrolyte balance. Membrane permeability disorders can also be caused by hereditary factors. For example, when membrane proteins mutate, this alters the permeability of the cell. This is the case, for example, in myotonia congenita Thomsen, which is associated with muscle dysfunction. The cause is a genetic mutation that results in altered chloride channels in the muscle fiber membranes and reduces membrane permeability for chloride ions. As a consequence, patients suffer from involuntary muscle contractions that are perceived as stiffness. Those affected can only open their closed fist or their closed eyes again with some delay. Membrane permeability in particular can also be affected by autoimmune diseases. Some of these diseases are directed against the biomembranes, for example the antiphospholipid syndrome. In addition, mitochondriopathies disrupt membrane permeability. Mitochondria are cell organelles known as the energy powerhouses of the cell and produce free radicals as a waste product of energy production. If these radicals are not rendered harmless, they destroy the membranes and thus disrupt permeability. Complaints related to psychological permeability can occur in the context of many mental illnesses and are usually due to a lowering of self-awareness, which can manifest itself in decreased permeability to impulses from the subconscious.
