ENDOCRINE

• Endocrine System


  Second messenger system of the body that uses chemical messages (hormones) released into the blood to control several major processes
• Processes controlled by hormones


  • Reproduction
  • Growth and development
  • Mobilization of body defenses
  • Maintenance of homeostasis
  • Regulation of metabolism

  
• Types of chemical signaling


  • Dedicated endocrine glands
  • Organs with endocrine function

  
• Hormones


  Mediators that control mechanisms in the endocrine system

  
• Classes of hormones


  • Proteins and polypeptides
  • Steroid hormones
  • Amine hormones
• Hypothalamus


  Controls secretions of the pituitary gland, produces releasing and inhibitory hormones, controlled by negative feedback

  
• Negative feedback


  Mechanism where the endocrine system is controlled

  
• Positive feedback


  Mechanism where the endocrine system is controlled

  
• Major endocrine glands


  • Anterior pituitary
  • Posterior pituitary
  • Thyroid
  • Parathyroid
  • Adrenal
  • Pancreas
  • Testes
  • Ovaries
  • Thymus
  • Pineal

  
• Growth hormone (GH)


  Regulates cell metabolism and growth, decreased production causes dwarfism, increased production causes gigantism and acromegaly

  
• Thyroid-stimulating hormone (TSH)


  Stimulates the thyroid gland
• Adrenocorticotropic hormone (ACTH)


  Stimulates the adrenal cortex
• Melanocyte-stimulating hormone (MSH)


  Stimulates melanocytes
• Follicle-stimulating hormone (FSH)


  In females, stimulates ovarian follicle development; in males, stimulates sperm cell production

  
• Luteinizing hormone (LH)


  In females, stimulates ovulation and progesterone production; in males, stimulates testosterone production
• Prolactin


  Stimulates milk production in females, may cause decrease in male sex hormones
• Antidiuretic hormone (ADH)


  Increases water reabsorption in kidney tubules, deficiency results in diabetes insipidus
• Oxytocin


  Contracts uterine smooth muscles, constricts mammary gland cells (lactation), given after childbirth to minimize risk of hemorrhage

  
• Thyroid gland


  Located below larynx on either side of trachea, requires iodine

  
• Thyroxine (T4) and Triiodothyronine (T3)


  Thyroid hormones that regulate metabolism

  
• Calcitonin


  Thyroid hormone that regulates calcium and phosphate concentration
• Hypothyroidism


  Cretinism, lowered metabolic rate, myxedema
• Hyperthyroidism


  Elevated metabolism, Graves' disease with exophthalmia
• Parathyroid glands


  Located within the posterior thyroid gland, secrete parathormone (PTH) which stimulates bone cell release of calcium and phosphate
• Hyperparathyroidism


  Breakdown of bone matrix
• Hypoparathyroidism


  Low calcium level in blood
• Adrenal glands


  Located on top of each kidney, adrenal medulla produces epinephrine and norepinephrine, adrenal cortex produces aldosterone, cortisol, and androgens

  
• Addison's disease


  Lack of adrenal cortex hormones
• Cushing's syndrome


  Too much adrenal cortex hormones
• Pancreas


  Islets of Langerhans contain beta cells that produce insulin and alpha cells that produce glucagon, blood glucose levels regulated by negative feedback
• Diabetes mellitus


  Insufficient insulin production
• Testes


  Produce testosterone, responsible for development of male reproductive structures and sex characteristics
• Ovaries


  Produce estrogen and progesterone, responsible for development of female reproductive organs and sex characteristics, control menstrual cycle

  
• Thymus gland


  Located behind the sternum, secretes thymosin which is important for T cell production, shrinks as we age
• Pineal gland


  Located in the brain near the thalamus, secretes melatonin which inhibits reproductive functions and regulates body rhythms, also secretes serotonin which is a neurotransmitter and vasoconstrictor