The Endocrine System


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The Endocrine System

  1. 1. The Endocrine System Chapter 17
  2. 2. The Endocrine System <ul><li>Affects bodily activities by releasing chemical messengers, called hormones, into the bloodstream. </li></ul><ul><li>Sends messages to cells in any part of the body. </li></ul><ul><li>Helps to regulate the activity of smooth and cardiac muscle and some glands. </li></ul><ul><li>Endocrine organs are widely scattered throughout the body. </li></ul><ul><li>The nervous and endocrine systems coordinate their activities and together are considered the control systems of the body. </li></ul>
  3. 3. The Ways Hormones Affect Targets <ul><li>The effects of hormones are many and varied, but their actions can be categorized into 5 broad areas: </li></ul><ul><li>1. Help control the internal environment. </li></ul><ul><li>2. Respond to changes in the environmental conditions to help the body cope with emergency demands such as infection, trauma, emotional stress, dehydration, starvation, hemorrhage, and temperature extremes. </li></ul><ul><li>3. Integration of growth and development. </li></ul><ul><li>4. Contribute to the basic processes of reproduction. </li></ul><ul><li>5. Help regulate organic metabolism and energy balance. </li></ul>
  4. 4. Endocrine and Exocrine <ul><li>Two kinds of glands in the body: endocrine and exocrine </li></ul><ul><li>1. Exocrine glands have ducts through which their non-hormonal products are routed to a membrane surface. Examples are sweat, sebaceous, mucous, and digestive glands. </li></ul><ul><li>2. Endocrine glands are ductless glands which release hormones directly into the blood and lymph.   </li></ul>
  5. 5. Chemical Classification of Hormones <ul><li>All hormones have in common the function of maintaining homeostasis by changing the rate of activities of cells. </li></ul><ul><li>  </li></ul><ul><li>They are classified chemically into one of two large groups of biochemical molecules: </li></ul><ul><li>amino-acid based hormones – Most hormones belong to this group. </li></ul><ul><li>steroid hormones – These hormones are synthesized from cholesterol. </li></ul>
  6. 6. Hormone-Target Cell Specificity <ul><li>A hormone influences the activity of only certain tissue cells. </li></ul><ul><li>The cell must possess specific protein receptors in order to respond to the hormone. </li></ul>
  7. 7. Types of Cellular Changes <ul><li>Hormones alter cell activity by increasing or decreasing the rates of normal cellular processes. </li></ul><ul><li>A hormonal stimulus typically results in one or more of the following changes: </li></ul><ul><li>1. Plasma membrane permeability </li></ul><ul><li>2. Synthesis of proteins or other regulatory molecules within the cell </li></ul><ul><li>3. Enzyme activation or deactivation </li></ul><ul><li>4. Induction of secretory activity </li></ul><ul><li>5. Stimulation of mitosis </li></ul>
  8. 8. Types of Stimulation that Cause Hormone Secretion <ul><li>Various endocrine glands are stimulated to manufacture and release their hormones by three main types of stimuli: </li></ul><ul><li>1. Hormonal – Hormones stimulate other endocrine glands to secrete other hormones. </li></ul><ul><li>Humoral – Hormone release is stimulated by substances dissolved in extracellular fluids. </li></ul><ul><li>Neural – In some cases, nerve fibers stimulate hormone release. </li></ul>
  9. 9. Pituitary Gland <ul><li>AKA the hypophysis </li></ul><ul><li>Secretes 9 major hormones </li></ul><ul><li>The size of a pea </li></ul><ul><li>Produces growth hormone (GH), which mobilizes fats for cells,. </li></ul>
  10. 10. Homeostatic Imbalances of the Pituitary Gland <ul><li>Gigantism – hypersecretion of GH, which causes a person to become abnormally tall. Often causes people to reach 8-ft, having relatively normal body proportions, though. </li></ul><ul><li>Acromegaly – causes excessive growth of the extremeties (hands, feet, face, etc.) </li></ul><ul><li>Dwarfism – deficiency of GH, causes individuals to only growth to 4-ft (or less) </li></ul>
  11. 11. Thyroid Gland <ul><li>The thyroid is a butterfly-shaped gland located in the anterior neck, overlying the trachea. </li></ul><ul><li>Largest pure endocrine gland in the body </li></ul><ul><li>1. Thyroid Hormone – referred to as the body’s major metabolic hormone. It stimulates enzymes concerned with increases in metabolic rate and body heat, and helps in tissue growth. </li></ul><ul><li>2. Calcitonin –It is released in response to high blood levels of calcium. Its function is to lower blood calcium levels by stimulating calcium uptake by bone. It is generally more important in childhood. </li></ul>
  12. 12. Parathyroid <ul><li>It is the most important hormone controlling calcium balance. Calcium is critically important for nerve impulse conduction, muscle contraction, and clotting. Its function is to increase blood calcium levels by stimulating three target organs: </li></ul><ul><li>Skeleton – causes digestion of bone and release of calcium </li></ul><ul><li>Kidneys – causes increased reabsorption of calcium from the forming urine and returns it to the blood </li></ul><ul><li>Small intestine – causes increased absorption of calcium by the intestinal cells </li></ul>
  13. 13. Adrenal Glands <ul><li>The paired adrenal glands are located on top of the kidneys where they are enclosed in a fibrous capsule and a cushion of fat. </li></ul><ul><li>All the hormones made are steroid hormones. </li></ul><ul><li>They are responsible for: </li></ul><ul><li>1. controlling the balance of minerals and water in the blood </li></ul><ul><li>2. secreting metabolic hormones </li></ul><ul><li>3. secreting small amounts of adrenal sex hormones   </li></ul>
  14. 14. Adrenal Glands <ul><li>Parts of the adrenal glands are stimulated by the sympathetic division of the autonomic nervous system. </li></ul><ul><li>Two powerful hormones are secreted: epinephrine and norepinephrine. </li></ul><ul><li>When the body is activated by a short term stressor or emergency the sympathetic nervous system is mobilized resulting in blood sugar level increases, vasoconstriction, and a faster heart rate. </li></ul>
  15. 15. Pancreas <ul><li>Located behind the stomach. </li></ul><ul><li>It is a mixed gland composed of both endocrine and exocrine gland cells.   </li></ul><ul><li>Insulin and glucagon are both involved in the metabolism and regulation of blood glucose </li></ul>
  16. 16. Glucagon <ul><li>Released in response to low blood sugar levels. </li></ul><ul><li>Its function is to raise blood sugar to the proper level. </li></ul><ul><li>Its major target is the liver where it promotes </li></ul><ul><li>the breakdown of glycogen to glucose and the formation of glucose from non-carbohydrate precursors such as fatty acids and amino acids. </li></ul>
  17. 17. Insulin <ul><li>Released in response to high blood sugar levels. Its function is to lower blood sugar to the proper level by the following mechanisms: </li></ul><ul><li>1. inhibits breakdown of glycogen to glucose </li></ul><ul><li>2. enhances transport of glucose into cells </li></ul><ul><li>3. promotes breakdown of glucose inside cells for ATP production </li></ul><ul><li>4. joins glucose together to form glycogen </li></ul><ul><li>5. converts leftover glucose to fat after the body’s immediate energy needs are met </li></ul><ul><li>  </li></ul>
  18. 18. Gonads <ul><li>Produce gonadal sex hormones, identical to those produced by adrenal cortex. </li></ul><ul><li>Sex hormones are steroid hormones. </li></ul><ul><li>Ovaries produce estrogen and progesterone. Estrogen is responsible for maturation of female reproductive organs and secondary sex characteristics of females at puberty. </li></ul><ul><li>The testes produce testosterone which is responsible for maturation of male reproductive organs, secondary sex characteristics of males at puberty, and the sex drive. </li></ul>