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Understanding the Endocrine System: Hormones and Homeostasis**

This video introduces the endocrine system, highlighting its vital role in maintaining homeostasis through the release of hormones. The endocrine system regulates growth, development, reproduction, metabolism, and the body's defenses. Hormones are secreted into the bloodstream by specialized cells and target specific tissues, influencing their function. Key mechanisms include feedback regulation, stimulating factors like hormones (hormonal), changes in nutrient levels (humoral), and nerve stimulation (neural). This overview covers major endocrine glands, including the pituitary, thyroid, and adrenal glands.

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Understanding the Endocrine System: Hormones and Homeostasis**

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  1. Chapter 9 Endocrine System

  2. Intro video • http://www.youtube.com/watch?v=-S_vQZDH9hY&feature=BFa&list=UUEik-U3T6u6JA0XiHLbNbOw&lf=plcp • Skip lipid/water section

  3. Endocrine function • MAINTAINS HOMEOSTASIS BY • RELEASING CHEMICALS CALLED HORMONES INTO THE BLOOD • CONTROLS GROWTH & DEVELOPMENT • CONTROLS REPRODUCTION • CONTROLS METABOLISM • MOBILIZATION OF BODY’S DEFENSES • MAINTAIN WATER/NUTRIENT BALANCE

  4. Hormone Overview • Hormones are produced by specialized cells • Cells secrete hormones into extracellular fluids • Blood transfers hormones to target sites • These hormones regulate the activity of other cells

  5. Mechanisms of Hormone Action • Hormones affect only certain tissues or organs (target cells or organs) • Target cells must have specific protein receptors • Hormone binding influences the working of the cells

  6. Effects Caused by Hormones • Changes in plasma membrane permeability or electrical state • Synthesis of proteins, such as enzymes • Activation or inactivation of enzymes • Stimulation of mitosis

  7. Control of Hormone Release • Hormone levels in the blood are maintained by negative feedback • A stimulus or low hormone levels in the blood triggers the release of more hormone • Hormone release stops once an appropriate level in the blood is reached

  8. STIMULI THAT ACTIVIATE ENDOCRINE ORGANS • HORMONAL • MOST COMMON • ENDOCRINE GLANDS ACT DUE TO OTHER HORMONES • EX: HYPOTHALAMIC --->ANT. PITUITARY --->OTHER ENDOCRINE ORGANS • HUMORAL • CHANGING BLOOD LEVELS OF CERTAIN IONS/NUTRIENTS STIMULATE HORMONE RELEASE • NEURAL • NERVE FIBERS STIMULATE HORMONE RELEASE

  9. STIMULI THAT ACTIVIATE ENDOCRINE ORGANS NEURAL HORMONAL HUMORAL

  10. MAJOR ENDOCRINE ORGANS • PITUITARY • HYPOTHALAMUS • THYROID • PARATHYROID • ADRENAL • PANCREAS • PINEAL • THYMUS • OVARIES/TESTES

  11. video • http://www.youtube.com/watch?v=Ry5fTZfZHIs&feature=related

  12. Pituitary Gland • Size of a grape • Hangs by a stalk from the hypothalamus • Protected by the sphenoid bone • Has two functional lobes: • Anterior pituitary – glandular tissue • Posterior pituitary – nervous tissue

  13. Pituitary Gland

  14. Anterior Pituitary Gland • Six anterior pituitary hormones • Two affect non-endocrine targets • Four stimulate other endocrine glands (tropic hormones) • Characteristics of all anterior pituitary hormones • Regulated by hormonal stimuli, mostly negative feedback

  15. Anterior Pituitary Gland

  16. HORMONES OF Anterior Pituitary Gland • Growth Hormone (GH) • General metabolic hormone • Major effects are directed to growth of skeletal muscles and long bones • Causes amino acids to be built into proteins • Causes fats to be broken down for a source of energy

  17. HORMONES OF Anterior Pituitary Gland • Prolactin (PRL) • Stimulates and maintains milk production following childbirth • Function in males is unknown • Adrenocorticotropic hormone (ACTH) • Regulates endocrine activity of the adrenal cortex • Thyroid-stimulating hormone (TSH) • Influences growth and activity of the thyroid

  18. HORMONES OF Anterior Pituitary Gland • Follicle-stimulating hormone (FSH) • Stimulates follicle development in ovaries • Stimulates sperm development in testes • Luteinizing hormone (LH) • Triggers ovulation • Causes ruptured follicle to become the corpus luteum • Stimulates testosterone production in males (ICSH)

  19. Pituitary - Hypothalamus Relationship • Release of anterior pituitary hormones is controlled by releasing and inhibiting hormones produced by the hypothalamus • Hypothalamus produces two hormones that are transported to neurosecretory cells of the posterior pituitary for storage • The posterior pituitary is not strictly an endocrine gland, but does release hormones

  20. HORMONES OF POSTERIOR PITUITARY • Oxytocin • Stimulates contractions of the uterus during labor • Causes milk ejection • Antidiuretic hormone (ADH) • Can inhibit urine production • In large amounts, causes vasoconstriction leading to increased blood pressure (vasopressin) • Hyposecretion can lead to diabetes insipidus

  21. HORMONES OF POSTERIOR PITUITARY

  22. Thyroid gland • Found at the base of the throat • Consists of two lobes and a connecting isthmus • Produces two hormones • Thyroid hormone • Calcitonin

  23. Thyroid hormone • Major metabolic hormone • Composed of two active iodine-containing hormones • Thyroxine • Triiodothyronine

  24. Calcitonin hormone • Decreases blood calcium levels by causing calcium to be deposited into the bones • Antagonistic to parathyroid hormone • Few effects of hypo- or hyper- are known • Meager production in adults --->decalcification w/ aging

  25. Parathyroid Glands • Tiny masses on the posterior of the thyroid • Secrete parathyroid hormone (PTH) • Stimulate osteoclasts to remove calcium from bone • Stimulate the kidneys and intestine to absorb more calcium • Raise calcium levels in the blood

  26. Adrenal Glands • Two glands • Cortex – outer glandular region • Medulla – inner neural tissue region • Sits on top of the kidneys

  27. Adrenal cortex hormones • Collectively called: • Corticosteroids • Mineralocorticoids • Glucocorticoids • Sex hormones

  28. Adrenal cortex hormones • Aldosterone (mineralocorticoid) • Regulate mineral content in blood, water, and electrolyte balance • Target organ is the kidney • Cortisone and Cortisol (Glucocorticoids) • Promote normal cell metabolism • Help resist long-term stressors • Released in response to increased blood levels of ACTH

  29. Adrenal cortex hormones • Sex hormones • Produced throughout life in small amounts. • Mostly Androgens (male) and some estrogen (female), regardless of gender

  30. Adrenal MEDULLA hormones • Produces two similar hormones (catecholamines) • Epinephrine (also called adrenaline) • Norepinephrine (similar to epinephrine) • These hormones prepare the body to deal with short-term stress • Stimulated by the sympathetic nervous system

  31. PANCREAS • The pancreas produces hormones: • Insulin – allows glucose to cross plasma membranes into body cells • Glucagon – allows glucose to enter the blood; stimulates liver to release glucose into the blood • These hormones are antagonists that maintain blood sugar homeostasis

  32. PANCREAtic islets • Aka – Islets of Langerhans • Scattered in pancreatic tissue • Where insulin & glucagon are produced • High levels of glucose in blood stimulate release of insulin from BETA cells • INSULIN sweeps glucose OUT of the blood • GLUCAGON acts as an antagonist of insulin ---> regulates blood glucose levels opposite of insulin • Released by ALPHA cells when blood sugar level is LOW

  33. Video • http://www.youtube.com/watch?v=qzjjW--I-2Q

  34. PANCREAtic islets

  35. Pineal gland • Found on the third ventricle of the brain • Secretes melatonin • Helps establish the body’s wake and sleep cycles • May have other as-yet-unsubstantiated functions

  36. thymus • Located posterior to the sternum • Largest in infants and children • Produces thymosin • Matures some types of white blood cells • Important in developing the immune system

  37. ovaries • HORMONE ESTROGEN: • Produced by Graafian follicles or the placenta • Stimulates the development of secondary female characteristics • Matures female reproductive organs • Helps prepare the uterus to receive a fertilized egg • Helps maintain pregnancy • Prepares the breasts to produce milk

  38. ovaries • HORMONE PROGESTERONE • Produced by the corpus luteum • Acts with estrogen to bring about the menstrual cycle • Helps in the implantation of an embryo in the uterus

  39. TESTES • Interstitial cells of testes are hormone-producing • Produce several androgens • Testosterone is the most important androgen • Responsible for adult male secondary sex characteristics • Promotes growth and maturation of male reproductive system • Required for sperm cell production

  40. Other Hormone-Producing Tissues and Organs • Parts of the small intestine • Parts of the stomach • Kidneys • Heart • Many other areas have scattered endocrine cells

  41. Endocrine Function of the Placenta • Produces hormones that maintain the pregnancy • Some hormones play a part in the delivery of the baby • Produces HCG in addition to estrogen, progesterone, and other hormones

  42. diseases

  43. Developmental Aspects of the Endocrine System • Most endocrine organs operate smoothly until old age • Menopause is brought about by lack of efficiency of the ovaries • Problems associated with reduced estrogen are common • Growth hormone production declines with age • Many endocrine glands decrease output with age

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