chapter 10

• Endocrine system


  Chemical control system that functions in conjunction with the nervous system to control the internal environment (homeostasis)
• Nervous System


  Uses chemical messengers called neurotransmitters
• Endocrine System


  Uses chemical messengers called hormones
• Nervous System vs Endocrine System

  • Location of message: synapses vs target cells
  • Effects: rapid & short-lasting vs slower & longer lasting
  • Controls: muscles & glands vs activities of cells
• Endocrine Glands


  Discharge secretions directly into the bloodstream, are ductless, and release chemical messengers called hormones
• Hormones


  • Have a specific target tissue which they may increase or decrease the activity of
  • Are not secreted at a constant rate, the rate varies with the needs of the body
• The endocrine system is in charge of processes that happen slowly, such as the growth of cells
• The glands and hormones of the endocrine system influence almost every cell and organ in the body
• Homeostasis


  A stable internal environment (nutrition, metabolism, excretion, water and salt balances)
• Feedback Mechanisms

  1. Stimulus: change in homeostatic environment, signal sent to CNS

  2. Response: signal sent from CNS produces effect & body returns to homeostasis
• Negative Feedback


  Response that opposes the original change - an increase in A will decrease in B, the most common control mechanism
• Positive Feedback


  Reinforces the original change - an increase in A will cause an increase in B, not common
• Hormones are the body's chemical messengers that send important information from one set of cells to another
• Each hormone only affects cells that are programmed to receive a specific hormone's message
• Glands


  Groups of cells that produce chemical products for our body to use
• Once hormone levels reach a certain amount, endocrine system glands will produce less of a specific hormone
• Endocrine glands are told to produce less of a hormone by substances in the blood or by the very hormone the gland is about to stop producing a large amount of
• Most hormones use a "turnoff" process called a negative feedback or a closed loop system
• Hypothalamus


  Also part of the brain, attached to the posterior pituitary gland, its function is to synchronize the information from the brain and the secretions of hormones
• Hypothalamus


  • Neurosecretory cells - specialized neurons that synthesize & secrete hormones
  • Controls the secretions of the pituitary gland through nervous stimulation (posterior pituitary) and releasing hormones secreted to the anterior pituitary
• Pituitary Gland


  Located at the base of the brain, considered the most important part of the endocrine system and is often called the "master gland", controls many other endocrine system glands, helps control body and tissue growth, secretes endorphins
• Anterior Pituitary


  • Secretes hormones that regulate many other glands: FSH, LH, TSH, ACTH, GH, MSH, Prolactin
• Posterior Pituitary

  • Secretes Oxytocin and Antidiuretic Hormone (ADH)
• Pineal Gland


  Located in the brain, secretes melatonin which regulates our internal clocks and any rhythmic activities
• Thyroid Gland


  Wraps around the trachea at the base of the neck, secretes thyroxine which regulates the metabolic rates of almost all the cells in the body
• Parathyroid Glands


  Four little glands embedded in the thyroid gland, secrete parathyroid hormone which regulates the amount of calcium in the blood and its absorption by bones
• Thymus Gland

  Located below the thyroid between the right and left lung, secretes thymosin which stimulates T-cell production in children
• Adrenal Glands


  Located on top of the kidneys, medulla secretes epinephrine and norepinephrine which regulate the fight or flight response, cortex secretes aldosterone and cortisol
• Pancreas


  Located behind the right side of the stomach, secretes insulin which tells the liver and muscles to remove sugar from the blood and store it as fat, also secretes glucagon which tells the liver to break down fat stores and release sugar back into the blood
• Ovaries


  Secrete estrogen and progesterone which regulate the female menstrual cycle
• Testicles


  Secrete testosterone which controls development of male characteristics
• Hyper


  Secretion of too much hormone
• Hypo


  Secretion of insufficient hormone
• Target cell insensitivity


  Produces symptoms similar to hypo secretion
• Pituitary Gland Disorders

  • Pituitary dwarfism
  • Giantism
  • Acromegaly
  • Diabetes insipidus
• Thyroid Gland Disorders

  • Cretinism
  • Myxedema
  • Grave's Disease
  • Goiter
• Parathyroid Gland Disorders


  • Hypoparathyroidism
  • Hyperparathyroidism
• Adrenal Gland Disorders

  • Cushing's Syndrome
  • Addison's Disease
  • Tumors of the adrenal medulla
• Pancreatic Disorders


  • Diabetes mellitus (Type I and Type II)
  • Hyperinsulinism
• Peptide and Amine Hormones


  Non-steroid, water-soluble, large, can't fit through membrane of target cell, bind to receptor on target cell triggering 2nd messenger to affect cell's activity