M12

• Autocrine or Paracrine


  Local messengers secreted by one cell type; ex: histamine
• Lipid-soluble or Water-soluble


  Most circulate as free hormones
• Humoral or Neural or Hormonal


  Directly by blood-borne chemicals to hormones
• Nuclear receptors or Membrane-bound receptors


  The hormone-receptor complex activates genes, which in turn activate the DNS to produce mRNA
• Anterior or Posterior


  Releases antidiuretic hormones
• Thyroid gland

  • Made up of two lobes connected by isthmus; located on each side of trachea & highly vascular
• Function of thyroid gland


  To secrete thyroid hormones which bind to nuclear receptors in cells & regulate rate of metabolism
• Thyroid hormones are synthesized and stored within thyroid follicles and attached to thyroglobulin

  
• Parafollicular cells / C cells secrete the calcitonin
• Hormones regulated by


  1. TSH-releasing hormone (TRH) from hypothalamus

  2. Thyroid-stimulating hormone (TSH) from anterior pituitary gland
• Goiter


  • Enlargement of thyroid gland; can develop from too low iodine in diet or excess in TSH

  
• Hypothyroidism


  • Lack of thyroid hormones

  
• Hypothyroidism conditions

  • Cretinism: hypothyroidism that occurs in infant which is characterized by mental retardation, short stature, and abnormally formed skeletal structures
  • Myxedema: occurs in adults; characterized by extremely lethargic, having a hard time performing routine task, and accumulation of fluid & other molecules in subcutaneous tissue of skin

  
• Hyperthyroidism


  • Elevated rate of thyroid hormones secretion that causes increased metabolic rate, extreme nervousness, & chronic fatigue
• Graves' Disease


  • An autoimmune disease that causes hyperthyroidism; occurs when immune system produces abnormal proteins that are similar in structure & function toTSH, over-stimulating thyroid gland

  
• Exophthalmia - bulging of the eyes associated with Graves' disease
• Parathyroid glands


  • Four tiny glands embedded in posterior wall of thyroid glands; release parathyroid hormone (PTH) which is considered more important the calcitonin in Ca2+ regulation

  
• Hyperparathyroidism


  • Abnormally high rate of PTH secretion usually caused by tumor in the gland; results to easily fractured bones, fatigue, muscle weakness, and kidney stones

  
• Hypoparathyroidism


  • Abnormally low rate of PTH secretion; may result from injury or surgical removal of thyroid & parathyroid glands; characterized by frequent muscle cramps & tetanus

  
• Adrenal glands


  • Two small glands located superior to each kidney; divided into adrenal medulla & adrenal cortex
• Renin-Angiotensin-Aldosterone System (RAAS)


  This system is activated when the blood pressure drops

  
• Pancreas


  • Has of pancreatic islets (islet of Langerhans) which consist of three cell types that are vital in regulation of blood levels of glucose
• Pancreatic islet cell types

  • Alpha Cells - secrete glucagon
  • Beta Cells - secrete insulin
  • Delta Cells - secrete somatostatin
• Acidosis - reduced pH of body fluids below normal; associated with breakdown of lipids releasing enough fatty acids & ketones when blood glucose levels are very low
• Hyperglycemia - very high blood glucose levels
• Diabetes Mellitus (DM)


  • Inability to regulate blood glucose levels within normal range; results of exaggerated appetite, excess urine production, dehydration, thirst, & fatigue; has two types:
  • Type 1 DM: occurs when too little insulin is secreted from pancreas
  • Type 2 DM: caused by either too few insulin receptors or defective receptors (do not respond normally to insulin) on target cells
• Insulin Shock


  • Too much insulin is present in blood; occurs when a diabetic injected too much insulin or has not eaten after an insulin injection; may result to disorientation, convulsion, & loss of consciousness
• Reproductive organs


  • Include testes in males & ovaries in females; hormone release is stimulated by LH& FSH
• Thymus


  • Lies in upper part of thorax; most important early in life for normal development of immune system in infant
• Pineal gland


  • Small, pinecone-shaped structure located in thalamus; play an important role in the onset of puberty
• Hormones secreted by cells in lining of stomach & small intestine

• Hormones from small intestine


  Help in regulation of rate at which food passes (stomach into the intestine)
• Prostaglandin


  Intercellular signal that are widely distributed in body & play a role in inflammation
• Prostaglandin causes relaxation of smooth muscles (ex: dilation of blood vessels) & contraction of smooth muscles (ex: uterine contraction during delivery); medically used to induce abortion
• Prostaglandin is produced by platelets for normal blood clotting

  
• Aspirin inhibits prostaglandin synthesis
• Atrial Natriuretic Hormone (ANH) / Atrial Natriuretic Peptide (ANP)


  Secreted by right atrium of heart in response to elevated blood pressure; inhibits Na+ reabsorption in kidneys resulting to more urine to be excreted

  
• Erythropoietin


  Secreted in response to reduced oxygen levels in kidneys; acts on bone marrow to increase production of RBC

  
• Human Chorionic Gonadotropin (HCG)


  Similar in structure & function of LH; secreted by placenta to maintain pregnancy & stimulate breast development
• Diabetes Insipidus


  • Due to lack of ADH; results in excessive urination