Physiology · MU Sofia

68. General principles of endocrine regulation. Chemical classes of hormones and hormonal mechanism of action. Regulation of hormonal secretion.

Covers the endocrine system's role in homeostasis and the three chemical classes of hormones: peptide and protein, steroid, and amine, with their synthesis and transport. It then explains how steroid and water-soluble hormones act on target cells, via G proteins and second messengers such as cAMP and IP3. The note closes with neural, negative, positive and long- and short-loop feedback control of hormone secretion, illustrated with examples and a recap question set.

Inside: 7 sections · 9 labelled pictures · 21 flashcards · 7 min

Topic 67 of 104 in the MU Sofia syllabus for Physiology (Dental Medicine, Year 2). The free AceMed note covers it in 7 sections, about 974 words (7 min of reading), with 21 flashcards.

In this note

  1. General principles of endocrine regulation. Chemical classes of hormones and hormonal mechanism of action. Regulation of hormonal secretion.
  2. Hormones
  3. Steroid Hormones
  4. Amine Hormones
  5. Transport
  6. Mechanisms of Hormone Action
  7. Regulation of Hormone Secretion

General principles of endocrine regulation. Chemical classes of hormones and hormonal mechanism of action. Regulation of hormonal secretion.

The endocrine system is a system of biochemicals that regulate distant tissues by means of secretion into the circulatory system. This system, along with the nervous system, is responsible for homeostasis. Growth, development, reproduction, blood pressure, concentrations of ions and other substances in the blood, and even behavior are all regulated by the endocrine system. Endocrine physiology involves the secretion of hormones and their subsequent actions on target tissues.

Hormones

A hormone is a chemical substance that is classified as a peptide, a steroid, or an amine. Hormones are secreted into the circulation in small amounts and delivered to target tissues, where they produce physiologic responses.

  • Hormones are synthesized and secreted by endocrine cells usually found in endocrine glands.
  • The classic endocrine glands are the hypothalamus, anterior and posterior lobes of the pituitary, thyroid, parathyroid, adrenal cortex, adrenal medulla, gonads, placenta, and pancreas.
  • The kidney is also considered an endocrine gland, and endocrine cells are found throughout the gastrointestinal tract.

Hormones are categorized into three classes: peptides and proteins, steroids, or amines.

Peptide and Protein Hormones- largest group

  • Most hormones are peptide or protein in nature.
  • Peptide and protein hormones are synthesized from amino acids.
  • Being hydrophilic and lipophobic (repelling fats), they cannot freely pass through the cell membrane. Their sizes vary widely and include hormones such as growth hormone, follicle-stimulating hormone (FSH), thyrotropin-releasing hormone (TRH), insulin, glucagon, leptin, ADH, and oxytocin.
  • These molecules bind to receptors located on the cell surface, triggering the activation of second messengers. These messengers then transmit the signal to produce a specific cellular response. Examples of second messengers include cyclic AMP (cAMP), calcium ions (Ca²⁺), nitric oxide (NO), and protein kinases.

Continue reading free

The whole note, all 7 sections, is free with an AceMed account, with its 21 flashcards. Premium adds flashcard recall, highlights and Ask AI.

Start freeAlready a member? Open the note