Where and how are neurohormones formed? What are neurohormones and what are their functions?

The structure and activity of intrasecretory glands is studied by such a science as endocrinology. Discipline also examines the different types of hormones, their interaction, the ways of their formation and the effect on the body.

What is a hormone?

It is a compound entering the bloodstream and penetrating it through various organs. Due to the activity of these substances, the activity of other cells, called targets, decreases or increases. Hormones through them affect almost all vital functions of the human body. The concentration of produced compounds depends on various factors. In particular, the time of day, age, emotional and physical condition is important. In the blood, hormones penetrate as needed, but are excreted unchanged in small amounts through bile or urine. There are different types of compounds that have some effect on the human condition. One of them are neurohormones. These compounds are produced in a special zone of the brain. What are these substances? How are neurohormones formed? What effect do they have on systems in the body? About this further.

General information

Before you find out where and how neurohormones are formed, you should understand what these substances are in general. The very definition has Greek roots. Literally translated as neuron (nerve) + hormaino (induce, set in motion). What is a neurohormone? These are biologically active peptide compounds. They enter the pituitary gland and regulate its activity. Neurohormones are produced by the hypothalamus. Due to the activity of the compounds under consideration, the endocrine and nervous systems are connected to each other. This is due to the fact that neurosecretory cells have a special susceptibility to the activity of mediators - compounds that transmit a pulse to the working organ from the nerve end. Thus, their participation extends to the regulation of the activity of intrasecretary glands during development and growth of the organism.

Classification

In this category of compounds, two groups are distinguished. The first include liberians. These substances have a stimulating effect on the production of tropic pituitary secrets. This group, in particular, includes corticoliberin and tyroliberin, folliberin, lyuliberin, somatoliberin, melanoliberin, prolactoliberin. The second group of non-neurohormones is statins. These compounds slow down the production of tropic pituitary secrets. This group, in particular, includes somatostatin, melanostatin and prolactostatin. According to the results of the conducted studies, the activity of neurohormones of the hypothalamus is not limited only by stimulation or inhibition of the production of biologically active tropic compounds. Substances have the ability to influence the processes of biosynthesis.

In what areas is the production carried out?

It was said above that the production of such compounds in humans occurs in a special zone of the brain. The formation of these substances occurs both in vertebrates and in invertebrates. Where and how are neurohormones formed in other organisms? In vertebrates, pinealocytes of the epiphysis, elements of chromaffin tissue in the adrenal medulla, ganglia, paraganglia and nerve trunks of the vegetative and peripheral nervous system participate in the secretion. In secretory granules, neurohormones, as a rule, bind to carrier proteins.

Some features

In contrast to the classical type of nerve cells, which produce chemical transmitters of nerve impulses - mediators, neurosecretory elements produce special compounds in the cytoplasm (in rare cases in the nucleus). These substances are allocated mainly through nerve endings (terminal) into the blood, hemolymph, spinal and tissue fluid. Neurohormones exert a regulatory influence on the activity of visceral organs (endocrine glands, in particular) and the central nervous system.

What are the functions of neurosecretory cells? The activity of these elements is controlled by classical neurons. Their axons form numerous synapses on the body and outgrowths of neurosecretory cells, which have the ability to generate an action potential and to propagate momentum along axons.

Location and concentration

Having found out, where and how neurohormones are formed, it is necessary to consider their distribution in the nervous system. Invertebrates of lower organisms are diffusely distributed. In phylogeny, the concentration of the bodies of neurosecretory cells in the corresponding centers is noted. Thus, in crustaceans there is an accumulation in the X-organ, and in insects, for example, in the protocerebrum. Neurohaemal organs and neurosecretory pathways appear. In vertebrates, the latter concentrate in a certain area of the intermediate brain (and in fish also in the caudal region of the spinal cord - urofize). As a result, two basic neurosecretory systems are formed: caudal (in fish only) and hypothalamic-pituitary.

Stages of development

Where and how are neurohormones formed? Synthesis of compounds associated with carrier proteins is performed on ribosomes. Accumulation takes place in the tubules of the endoplasmic reticulum. Elementary granules are finally formed in the Golgi complex. These components, whose diameter is from 50 to 500 nm, have a lipoprotein membrane. It is separated from the electron-dense center. It, in turn, consists of a carrier protein and a neurohormone. Moving of the granules is carried out towards the axons. Some axons contact the capillaries in the neurohypophysis. Others - with glandular cells in the adenohypophysis (mainly its intermediate lobe). In fish, axons of the caudal neurosecretory system create axoventricular contacts. Direct isolation of the contents from the granules is carried out in the contact data area by means of exocytosis or into the derivatives of the neurohumeral organs, into precapillary space and into intercellular spaces at the molecular level.

Possible pathologies

Neurohormones take part in the maintenance of hemostasis (water-salt and others), various aspects of metabolism, regulation of the tone of smooth muscles. In addition, due to their activity, the stable activity of the elements of the endocrine glands is ensured. Also, the functioning of the peptide compounds under consideration contributes to the protective-adaptive reactions of the organism. When entering the hemolymph, into the cerebrospinal fluid or into the tissue fluid, they have a long-term, distant regulatory effect. In the case of serious disorders of the hypothalamus and the development, respectively, of hypothalamic neurohormones, there are disruptions in the production of hormones in the pituitary gland and in other intrasecretory glands. At the person various pathologies of endocrine system start to develop . In particular, they include hypothalamic-pituitary insufficiency, Isenko-Cushing's disease, acromegaly, hypothyroidism and other ailments.