BIO10004_6.2_Endocrine System - 2 PDF

Department of Health Sciences and Biostatistics Anatomy and Physiology Bio10004-2024 Endocrines Dr. Greg Davis Copyright notice Learning objectives At the end of this lecture you should be able to: 1. Describe the essential characteristics of the endocrine system; be able to ex...

Department of Health Sciences and Biostatistics Anatomy and Physiology Bio10004-2024 Endocrines Dr. Greg Davis Copyright notice Learning objectives At the end of this lecture you should be able to: 1. Describe the essential characteristics of the endocrine system; be able to explain key distinctions between the nature of cellular communications in the endocrine system and nervous system 2. Identify three different classes of hormones (amino acid, protein, lipid derivatives). Predict the location and type of receptor found on the target cell based on the class of hormone involved in signalling. 3. Describe how negative feedback regulation controls hormone secretion. 4. Explain the roles of the hypothalamus, anterior and posterior pituitary glands have in control of endocrine function. (Describe the functional difference between hormones released and synthesised in the hypothalamus, anterior and posterior pituitary glands and “target” glands) 5. Describe the function of thyroid hormone in the body, and how its secretion is regulated. 6. Explain how blood glucose levels are regulated in the body, and explain how disruption of the glucostasis leads to diabetes. Endocrines Learning objective Describe the essential characteristics of the endocrine system; be able to explain key distinctions between the nature of cellular communications in the endocrine system and nervous system. Intercellular communication Several communication systems between cells Direct communication Via gap junctions Paracrine communication Within the same tissue Autocrine communication Within same cell Endocrine communication Hormones to relay messages Endocrine vs nervous Both systems coordinate and maintain human biology Nervous Endocrine – targets specific cells to action – reaches nearly all cells – action short lived (milliseconds, seconds) – action is long lasting (minutes, hours, days) – neurotransmitters – hormones – negative feedback control – negative feedback control Endocrine locations Classes of hormones These are largely of 3 separate types, with differences in (production, action and effects) Amino acid Peptides Lipid derivatives There are two classes of lipid derivatives: eicosanoids derived from arachidonic acid a 20-carbon fatty acid· and steroid hormones, derived from cholesterol. Eicosanoids Eicosanoids o (T-ko-sa-noydz) are important paracrines that OH OH Steroid Hormones coordinate cellular Prostaglandin E activities and affect enzymatic Steroid hormones are processes (such as blood clotting released by the reproductive OH in extracellular fluids). Some organs (androgens by eicosanoids such as leukotrienes the testes in males (lu-ko-TRi-ens) have secondary estrogens and HO t0 roles as hormones. A second progesterone by the E5 ' gen group of eicosanoids­ ovaries in females) by the prostaglandins-are involved cortex of the adrenal glands primarily in coordinating local (corticosteroids) and by the cellular activities. In some tissues kidneys (calcitriol). Because prostaglandins are converted to circulating steroid hormones thromboxanes (throm-BOX-anz) and prostacyclins (pros-ta­ are bound to specific transport ST-klinz) which also have proteins in the plasma they strong paracrine effects. remain in circulation longer than ,. r do secreted peptide hormones. Aspirin suppresses the production of prostaglandins. @ 2018 Pearson Education, Inc. Transport and inactivation Transport: Hormones are released very rapidly into capillaries beds Diffuse quickly throughout the body via circulation Inactivation occurs when: – Binds to receptors on target cells – Absorbed or broken down by cells, liver or kidneys – Broken down by enzymes Receptors and action Hormones can either cross cell membrane or not – If they cross, then they will directly activate cell function – This is first messenger action – If they cannot cross, rely on second messenger (G-protein) Pituitary Gland Anterior portion – Releases hormones controlled by hypothalamus Posterior portion – Releases hypothalamic hormones Thyroid gland Ductless gland Inferior to larynx Two lobes Most noticeable with problems Releases T3 T4 hormones Bind to receptors – Cytoplasm – Mitochondria – Nucleus Increase rate of ATP production in mitochondria Adrenal glands also known as suprarenal glands, are small, triangular-shaped glands located on top of both kidneys. Adrenal glands produce hormones that help regulate: Metabolism Immune System Blood Pressure Response To Stress Other Essential Functions Adrenal glands Pancreas and blood glucose Pancreas is endocrine gland and exocrine organ – Exocrine (ducted) produces trypsinogen (for digestion) 99% of mass – Endocrine has islet cells that produce hormones (1% of mass) – Alpha cells produce glucagon – Bet cells produce insulin – Delta cells produce Growth hormone inhibiting hormone – Polypeptide cells pancreatic polypeptide (control exocrine function) Histology of pancreas Control of blood glucose Critical function for cells Blood glucose levels need to be tightly controlled Circulating energy in the body Complex balance between storing and releasing Pancreas manages this with its separate hormones Summary Endocrines Comparison with nervous system 3 classes of hormones (amino acid, protein, lipid) Feedback control Hypothalamus, pituitary (master control) Target glands and their hormones Thyroid and thyroid hormones Pancreas and pancreatic hormones Control of blood glucose Diabetes Mellitus