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Endocrine System. Chapter 9. Endocrine Organs. Hormones. Chemical messengers that are released from one tissue and transported through blood to a target tissue. Chemical classification: amino acids, steroids, prostaglandins Receptors on target organ determine effect of hormone

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Endocrine system

Endocrine System

Chapter 9


  • Chemical messengers that are released from one tissue and transported through blood to a target tissue.

  • Chemical classification: amino acids, steroids, prostaglandins

  • Receptors on target organ determine effect of hormone

  • Hormone effects

    • Membrane permeability

    • Production of proteins or enzymes

    • Activation or inactivation of enzymes

    • Stimulation of cell division

    • secretion

Hormone action direct
Hormone Action (Direct)

  • Lipid soluble

  • Receptors are in nucleus

  • Receptor hormone complex binds to DNA

  • Gene activation

  • Testosterone and estrogen

Hormone action indirect
Hormone Action (Indirect)

  • Receptors on plasma membrane

  • G-Protein Coupled Receptors

  • 2nd messengers

  • Epinephrine, calcitonin

Pineal gland
Pineal Gland

  • Secretes melatonin

  • Lack of light stimulates secretion

  • Regulates sleep/wake cycles (circadian rhythms)

  • Possible link to fertility


Anterior Pituitary

Posterior Pituitary

Homeostatic imbalances
Homeostatic Imbalances

  • Pituitary Dwarfism (GH hyposecretion)– body is porportional, miniature (4 feet or less)

  • Gigantism (GH hypersecretion)– body is proportional, giant (8-9 feet)

  • Acromegly (hypersecretion) – after long bones growth ends, distorted facial features, elongated

  • Sterility due to hyposecretion of LH and FSH

Pituitary hypothalamic relationship
Pituitary-Hypothalamic Relationship

  • Hypothalamus regulates or controls pituitary

  • Portal system which serves anterior lobe

  • Hypothalamic neurons extending into posterior lobe

Thyroid gland
Thyroid Gland

  • Follicle cells secrete thyroglobulin

    • Regulated by TSH

    • Thyroglobulin is converted to T3 and T4 in the presence of Iodide

    • More T4 is secreted however T3 is more effective

    • Increases metabolism by controlling the breakdown of glucose

  • Parafollicular cells secrete calcitonin

    • Regulated by blood calcium levels

    • Decreases blood calcium levels, stimulating osteoblasts

Homeostatic imbalances1
Homeostatic Imbalances

  • Goiters – enlarged thyroid due to low levels of iodine, lack of feedback loop to stop production of thyroglobulin

  • Cretinism (hyposecretion in child) – dwarfism with disproportional body. Large head and trunk with shortened legs

  • Myxedema (hyposecretion in adult)- slow mentally and physically, obesity, low body temperature

  • Graves’ Disease (hyperthyroidism) –enlarged thyroid gland, bulging eyes


  • Secretes parathyroid hormone (PTH)

  • Is the most important regulator or controller of blood calcium levels

  • Regulated by blood calcium levels

    • Decrease in blood calcium triggers release of PTH

    • Stimulates osteoclasts to degrade bone

  • Homeostatic Imbalance –tetany caused by overactive neurons, fragile bones

Adrenal glands
Adrenal Glands

  • Structurally and functionally two endocrine glands

  • Medulla is neural in origin

    • Secretes catacholamines

    • Regulated by fear or stress

    • Short term stress response

    • Increase: HR, BP, blood glucose, dilates bronchioles

  • Cortex has three regions

    • Secretes corticosteroids

    • Regulated by ACTH

    • Aldosterone –regulates blood sodium levels

    • Cortisone & cortisol – increase blood glucose levels, reduce inflammation

    • Testosterone and estrogen

Homeostatic imbalances2
Homeostatic Imbalances

  • Addison’s Disease (hyposecretion of glucocorticoids) –electrolyte imbalance, weakness, hypoglycemia, immune suppression, bronze colored skin

  • Hyperaldosteronism –retention of excessive amounts of Na+ and H20, edema, low K+ effects HR

  • Cushing’s Syndrome (hypersecretion of glucocorticoids) –high BP, hyperglycemia, fragile bones, fat deposition on upper back, swollen face, immune depression

  • Masculinization (hypersecretion of testosterone) –masculine body hair, masked in males


  • Exocrine and endocrine gland

  • Endocrine gland resides in Islets of Langerhans

    • Beta cells secrete insulin which lowers blood glucose

    • Alpha cells secrete glucagonwhich breaks down glycogen (stored glucose) raising blood glucose levels

Homeostatic imbalances3
Homeostatic Imbalances

  • Diabetes mellitus – high blood sugar

    • Type I Diabetes (juvenile) –nonfunctioning Beta cells, no insulin is produced

    • Type II Diabetes (insulin resistant) –nonfunctioning insulin receptors, unable to detect insulin

  • Three signs of diabetes: polyuria, polydipsia, polyphagia

  • Ketosis –blood becomes acidic due to breakdown of stored fats, leads to coma and death

Other endocrine glands
Other Endocrine Glands

  • Thymus –matures T Lymphocytes

  • Gonads –estrogen and testosterone

  • Placenta –maintains pregnancy

  • GI Tract –regulates digestion