signalstoffet

Signalstoffet, literally the signaling substance, is a term used in biology to describe any molecule released by a cell that influences the behavior, function, or state of another cell. These molecules are central to intercellular communication and can act locally or over longer distances.

Signalstoffet types and modes of action include autocrine, paracrine, endocrine, and juxtacrine signaling. They can be neurotransmitters, hormones, cytokines, lipids, or gases. Chemically, they range from small molecules to peptides, proteins, and lipids. Release usually occurs by exocytosis or diffusion, and the signaling range depends on stability, degradation, and transport mechanisms.

Reception and signaling involve target cells bearing appropriate receptors. Receptors may be on the cell surface or inside the cell, depending on the signaling molecule’s properties. Upon binding, signal transduction cascades are activated, often involving secondary messengers such as cyclic AMP, IP3/DAG, calcium, or kinases. These pathways regulate enzyme activity, gene expression, metabolism, or cell behavior, enabling coordinated responses across tissues.

Examples and roles of signalstoffet are broad. In the nervous system, neurotransmitters like acetylcholine, dopamine, and serotonin convey rapid signals across synapses. Hormones such as insulin and adrenaline coordinate metabolism and stress responses. Cytokines guide immune activity, while gases like nitric oxide act as local messengers affecting vascular tone and circulation. Overall, signalstoffet underpins development, homeostasis, and adaptation, and its dysregulation is linked to numerous diseases.