Structure and functions of the hypothalamic-pituitary system

It’s no secret that the brain is an amazing place: neurons transmit signals to each other at incredible speeds, blood saturates cells with nutrients, and glands produce hormones – special substances that affect the various organs and tissues of the body, thus regulating their proper functioning.

The endocrine glands (in the brain, the hypothalamus and pituitary glands) work hard to keep your body functioning optimally. Whatever the hormone is, it works like this: a special endocrine cell receives a signal and begins to secrete the hormone, and the target cell that is subsequently affected by the hormone undergoes the necessary physiological changes.

The hypothalamus is located in the centre of our brain, between the two large hemispheres. Its main function is to maintain the homeostasis of our body (i.e. the stability of its internal environment).

Through the pituitary gland, the hypothalamus links the two regulatory systems of the body – the nervous and endocrine systems. The hypothalamus, like a parade commander, signals to the pituitary gland that it is time to produce hormones. Thus, the pituitary gland controls metabolism, growth, puberty, reproduction, blood pressure and many other vital physical functions and processes.

There are also neurons in the hypothalamus that are involved in autonomic regulation: through the sympathetic (activating) and parasympathetic (slowing down) systems, they control the activity of our internal organs. Take thermoregulation, for example. If the blood flowing through the hypothalamus is too warm, through the sympathetic nerves it triggers reactions aimed at lowering the body temperature of the whole organism: our skin vessels dilate and we start sweating profusely. In addition, the hypothalamic-pituitary system regulates our basic biological needs: the centres of hunger and thirst, the centres of sexual and parental behaviour, the centres of fear and aggression are located here.

Complicated and incomprehensible? Let’s try to imagine the hypothalamus as a big brother of the pituitary gland: it not only controls the actions of the pituitary gland, but also secretes hormones independently, like an adult, thus “managing” almost all the processes of our organism. Moreover, the cells of the hypothalamus constantly control the concentration of hormones already in our blood, and if the hypothalamus suddenly realises that there is a failure in the system, it gives a command to the pituitary gland to secrete more or less of a certain substance.

Attached to the hypothalamus, the pituitary gland stores hormones from the hypothalamus and releases them into the bloodstream. It is often called the body’s “master gland” because it controls the activity of most other hormone-secreting glands. The pituitary gland, despite its small size, is divided into two lobes: the posterior pituitary gland (neurohypophysis), made up of neurons, and the anterior pituitary gland (also known as the adenohypophysis), which is a true glandular (i.e. hormonal) tissue that develops (you won’t believe it!) from the digestive tract at the embryo stage.

Thus, the hypothalamic-pituitary system is engaged in both directing and executive work: regulating the activity of other endocrine glands of our organism, it regulates the constancy of the internal environment of the organism through the synthesis of its own hormones.