tailieunhanh - Ebook BRS cell biology and histology (6th edition): Part 2

(BQ) Part 2 book "BRS cell biology and histology" presents the following contents: Endocrine system, skin, respiratory system, digestive system - Oral cavity and alimentary tract; digestive system - Glands, digestive system: glands, female reproductive system, male reproductive system, special senses. | chapter 13 Endocrine System I. OVERVIEW THE ENDOCRINE SYSTEM A. The endocrine system is composed of several ductless glands clusters of cells within certain organs and isolated endocrine cells so-called diffuse neuroendocrine system DNES cells in the epithelial lining of the gastrointestinal and respiratory systems. B. Glands of the endocrine system include the pituitary thyroid parathyroid adrenal and pineal glands. C. Function. The endocrine system secretes hormones into nearby capillaries and interacts with the nervous system to modulate and control the body s metabolic activities. II. HORMONES Hormones are chemical messengers that are carried via the bloodstream to distant target cells. Hormones include low-molecular-weight water-soluble proteins and polypeptides . insulin glucagon follicle-stimulating hormone FSH and lipid-soluble substances principally the steroid hormones . progesterone estradiol testosterone . A. Water-soluble hormones interact with specific cell surface receptors on target cells which communicate a message that generates a biological response by the cell. 1. G protein-linked receptors are used by some hormones . epinephrine thyroidstimulating hormone TSH serotonin . Binding of the hormone to the G protein-linked receptor leads to production of a second messenger that evokes a target cell response. 2. Catalytic receptors are used by insulin and growth hormone. Binding of the hormone to the catalytic receptor activates protein kinases that phosphorylate target proteins. B. Lipid-soluble hormones diffuse across the plasma membrane of target cells and bind to specific receptors in the cytosol or nucleus forming hormone-receptor complexes that regulate transcription of deoxyribonucleic acid DNA . III. OVERVIEW PITUITARY GLAND HYPOPHYSIS The pituitary gland lies below the hypothalamus to which it is structurally and functionally connected. It is divided into two major subdivisions the adenohypophysis and the neurohypophysis Figure