19 topics with concise summaries: definitions, key facts, and class questions.
This section is dedicated to our body's chemical factory: the endocrine system. Here, we break down how hormones precisely control physiological processes: from maintaining glucose and calcium homeostasis to large-scale survival mechanisms during stress.
Inside you will find a comprehensive knowledge base covering all links of hormonal regulation. You will study the classification, structure, and synthesis of hormones, as well as their reception and circulation mechanisms. We will take a detailed look at the main regulatory "axis" (the hypothalamo-pituitary system) and examine the function of peripheral organs: the thyroid gland, pancreas, adrenal glands, reproductive system, and even the endocrine functions of the kidneys and heart.
Tip: in seminars and exams, negative feedback loops, cellular signal transduction mechanisms, and the specific effects of individual hormones (especially ACTH, somatotropin, and thyroid hormones) are tested most strictly. Pay special attention to the physiology of stress and adaptation—mastering these processes will be your trump card in clinical departments.
What is the difference between a hormone and a neurotransmitter?
The boundary between them is conventional. A substance is considered a hormone if it is secreted by an endocrine cell into the bloodstream (like adrenaline in the adrenal glands). The same substance is considered a neurotransmitter if it is released at nerve endings (like adrenaline in the sympathetic system).
What is the main feature of endocrine glands?
They completely lack excretory ducts. Produced hormones are released directly into the internal environment (into the rich capillary network), bypassing any external cavities.
What serves as the basis for the synthesis of steroid hormones?
All steroid hormones (both sex hormones and adrenal cortex hormones) are formed from a cholesterol molecule.
Can a hormone in a protein complex exert a biological effect?
No, only the freely circulating hormone has a physiological effect. The bound form serves as a dynamic reserve protecting the hormone from rapid degradation.
What is a permissive effect in simple terms?
This is the creation of a «favorable background». The hormone does not trigger a response directly, but prepares the cell (e.g., by increasing receptor sensitivity) so that another hormone can successfully work.
Why do protein hormones need membrane receptors?
Protein hormones are hydrophilic and incapable of dissolving in lipids, which is why they cannot cross the cell membrane. They must transmit signals via cell surface receptors.
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