Messenger substances are chemical substances with different structures that transmit signals between organisms or between the cells of an organism in different ways. These are chemically completely different substances or groups of substances. They are usually classified according to their function or effect. There are smooth transitions in the classification, which are often very arbitrary.

For example, compounds that perform similar functions can have completely different chemical structures. Every organism, regardless of whether it is a plant, animal or human, sends out messenger substances and also receives messenger substances at the same time. The same is also true for every cell within an organism. With regard to their function, messenger substances are divided into hormones, kairomones, neurotransmitters , parahormones, pheromones or phytohormones. According to the mode of action, a distinction is also made between intra- and interspecific signaling substances.

Intraspecific messengers exchange information within the species, while the interspecific messengers are responsible for communication between species. Thus, the intraspecific active ingredients are referred to as pheromones. The interspecific messengers are known as allochemicals. However, pheromones and allochemicals only include the part of the signaling substances that cause communication between organisms. Hormones and neurotransmitters, in turn, transmit signals between the cells or even within the cells of an organism.

Anatomy & Structure

Hormones are among the most important messenger substances within the organism. They control the metabolic processes in the body. They are either transferred from cell to cell or reach a target organ from a hormone-producing organ (endocrine gland) via the blood or serum. There are also hormones that work inside the cell, where they are made. What all hormones have in common is the exercise of control and regulatory functions within the organism.Chemically they are completely heterogeneous. For example, there are steroid hormones, steroid-like hormones, peptide hormones and hormones with a different chemical structure. Parahormones, on the other hand, control bodily functions, but do not meet all the criteria of hormones. The parahormones include, for example, carbon dioxide, which is involved in controlling respiratory functions. Another group of important messenger substances are the neurotransmitters. They are the signaling substances of the nervous system and develop their effect by binding to so-called receptors .

Their effect is limited to the nerve cells . Pheromones, another group of signaling substances, are emitted by an organism and received again by an organism of the same species. Allochemicals are chemical messengers that are sent out by one organism and received by an organism of another species.

Functions & Tasks

The only common property of all messenger substances is their function of transmitting information and thereby triggering reactions at the target site. However, the form of information transmission and the chemical structure of the signal substances differ significantly. Hormones have the task of controlling and controlling metabolic processes and regulatory mechanisms within the organism.

They are largely responsible for the function of the individual organs. They regulate, among other things, growth, mineral balance, blood sugar levels , sexual functions, energy metabolism and even the function of other hormones within the organism. The neurotransmitters have a localized effect on the nervous system. They excite and inhibit the nerve cells and ensure the transmission of stimuli. They develop their effect by docking to special receptors.

Among other things, they generate feelings of happiness, suppress pain or produce reactions to certain stimuli. Known neurotransmitters are the endorphins or the cytokines. Pheromones, in turn, control the behavior of the organisms of a species. Among other things, they also influence how people live together. Sympathy and antipathy also develop on the basis of pheromones. Allochemicals are messenger substances that influence the behavior of organisms of different species.

Diseases

Due to the diverse functions of messenger substances, disturbances in their interaction can cause serious health problems. Improper regulation in the endocrine system in particular leads to hormonal diseases. Overfunctioning or underfunctioning of individual endocrine organs develop typical symptoms. How insulin regulates blood sugar levels. Diabetes mellitus occurs when there is a lack of insulin .The thyroid produces the thyroid hormones thyroxine and triiodothyronine. They regulate the energy metabolism. When the thyroid gland is overactive , the metabolism accelerates dramatically, while when the thyroid gland is underactive, the metabolism slows down with the development of depression , fatigue and poor performance. If the adrenal cortex produces too much cortisol , the typical symptoms of Cushing’s syndrome appear with trunk obesity , a full moon face , increased blood sugar levels and weakening of theimmune system .

If even superordinate organs of the endocrine system become ill, this often leads to complex disease progressions due to the failure of several hormones at the same time. A case in point is panhypopituitarism . The anterior pituitary gland becomes diseased , which can lead to the failure of all seven hormones that are formed there. If the mother’s pituitary gland is destroyed during childbirth , what is known as Sheehan’s syndrome develops . Not only a hormone deficiency or excess can lead to diseases.

Dysregulations in the functioning of neurotransmitters are also often the cause of serious illnesses. These are usually neurological or psychological disorders. Depression is often caused by a lack of dopamine . Its binding to receptors can also be disturbed. On the other hand, dysregulation of neurotransmitters can also cause diseases such as Parkinson’s or epilepsy .