tailieunhanh - Ebook BRS Cell biology and histology (7th 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, the urinary system, female reproductive system, male reproductive system, special senses. | chapter 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 single endocrine cells known as the diffuse neuroendocrine system DNES cells located in the epithelial lining of the respiratory and gastrointestinal systems discussed in chapters 15 and 16 respectively . B. Glands of the endocrine system include the pituitary gland and a region of the brain known as the hypothalamus as well as the thyroid parathyroid adrenal and pineal glands. Additional components of the endocrine system such as the Islets of Langerhans adipose tissue female gonads and male gonads are discussed in the pertinent chapters. 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. Hormones are chemical messengers that are carried via the bloodstream to distant target cells. They include low-molecular-weight water-soluble proteins polypeptides and amino acids . insulin glucagon follicle-stimulating hormone FSH and lipid-soluble substances principally the steroid hormones . progesterone estradiol and 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 thyroid-stimulating hormone TSH serotonin . Binding of the hormone to the G protein-linked receptor leads to the 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 in the nucleus forming hormone-receptor .