Hormones and the Endocrine System (ch. 45)
  • Intercellular communication: endocrine, paracrine, autocrine, synaptic, and neuroendocrine signaling
    • The ways signals are classified are usually by two characteristics: the type of secreting cell and the route that is taken by the signal when trying to get to its intended target.
    • The following figure explains each type of signalling: endocrine, paracrine, autocrine, synaptic, and neuroendocrine
  • Water-soluble vs. Lipid-soluble hormones
    • Water-soluble hormones
      • Such as peptides and derivatives of amino acids.
      • Repelled by fats/lipids, like the lipids in cell and nucleus membranes.
      • They are soluble to water, so they will easily travel in blood
      • they tend to bind to receptors that are outside of the cell, because they can not cross the membrane.
    • Lipid-Soluble molecules
      • Such as sex hormone steroids (estrogen, androgen, etc.)
      • Lipid soluble, water repellent
      • They usually travel in a special carrier protein, so they can go through the water.
    • Carrier proteins
      • These special carrier proteins are soluble to water and lipid, so they can carry peptide and amino acid derivatives into lipid "areas", and they can carry sex hormone steroids into water "areas"
  • Local regulators
    • A molecule that when secreted, influences molecules all around from where it was secreted.
      • example: Cytokines
  • Coordination of endocrine and neuroendocrine signaling
    • In all animals (excluding simple invertebrates), the endocrine and nervous systems coordinate together to control reproduction and development
      • Example: Life Cycle of butterfly
      • butterflies grow in stages
      • PTTH (prothoacicotropic hormone) helps the process go, this eventually leads to a successful molt.
      • Juvenile Hormone (JH): As the process goes on, JH goes down, as it becomes an adult.
      • The figure below describes the rest of the details.
  • Simple endocrine and neuroendocrine pathways
    • Simple endocrine pathways
      • endocrine cells directly respond to an internal or environmental source by secreting a secreting a certain hormone. The hormone travels through the bloodstream to the target cells, in which it will interact with specific receptors.
    • Simple neuroendocrine pathways
      • Rather than the environment or an internal source, the cells respond to a sensory neuron, which stimulates a neurosecretory cell. That cell then secretes a neurohormone that diffuses into the bloodstream and it travels to its target cells.
  • Feedback regulation
    • Negative feedback: A form of regulation in which accumulation of an end product slows the process
    • Positive feedback: A form of regulation in which the lack of an end product speeds up the process.
    • Negative feedback and positive feedback combined is what is known as Feedback regulation.
  • Blood glucose control in humans, effects of diabetes mellitus
    • Blood glucose control in humans
      • When glucose is high in system, causes negative feedback, and the release of insulin into the system
      • When glucose is low in the system, cuases positive feedback, and the release of glucagon into the system.

    • Diabetes Mellitus
      • An endocrine disease that causes the body to be unable to regulate glucose levels
        • type 1 results from autoimmune destruction of insulin secreting cells
        • type 2 results from reduced responsiveness of target cells to insulin; obesity and lack of exercise increase chances for type 2 diabetes.
        • 90% of people with diabetes have type 2 diabetes.
  • Coordination of endocrine and nervous systems in vertebrates: hypothalamus and pituitary function and hormones
    • Hypothalamus function
      • the hypothalamus controls: autonomic nervous system, thirst, hunger, temperature in the body, pituitary gland, and emotions.
    • Hypothalamus hormones
      • The hormones of the hypothalamus are Oxytocin and Antidiuretic hormone (ADH)(aka vasopressin), but these hormones are released by the posterior pituitary gland.
    • Functions of the Pituitary gland
      • The pituitary gland controls: metabolism, growth/maturation, sexuality, reproduction, etc.
    • Pituitary gland hormones
      • Hormones of the Pituitary gland
        • Hormones of the Posterior Pituitary gland
          • Oxytocin: stimulates contraction of uterus and mammary glands
          • Antidiuretic Hormone (ADH) (aka vasopressin): promotes water retention in the kidneys
        • Hormones of the Anterior Pituitary gland
          • Growth Hormone (GH): Stimulates growth(especially in bones) and metabolic functions
          • Prolactin: Stimulates the production and secretion of milk
          • Follicle-Stimulating Hormone (FSH): stimulates production of ova and sperm
          • Luteinizing Hormone (LH): Stimulates ovaries and testes
          • Thyroid-Stimulating hormone (TSH): Stimulates the thyroid gland
          • Adrenocorticotropic hormone (ACTH): Stimulates adrenal cortex to secrete glucocorticoids
  • Other major human endocrine glands and hormones: thyroid, parathydroid, adrenal, pineal
    • Hormones of the Thyroid gland
      • Triiodothyronine (T3) and thyroxine (T4): Stimulate and maintain metabolic processes.
      • Calcitonin: Lowers blood calcium levels
    • Hormones of the Parathyroid gland
      • Parathyroid hormone (PTH): raises blood calcium levels
    • Hormones of the Adrenal Gland
      • Hormones of the Adrenal Medulla
        • Epinephrine and norepinephrine: Raises blood glucose level;increases metabolic activity;constricts certain blood vessels
      • Hormones of the Adrenal cortex
        • Glucocorticoids: Raises blood glucose level
        • Mineralcorticoids: Promotes reabsorption of Na+ and excretion of K+ in the kidneys
    • Hormones of the Pineal gland
      • Melatonin: Involved in biological rhythms (sleep)
  • Tropic vs. nontropic hormones
    • Nontropic hormones are hormones that directly stimulate target cells to induce effects.
      • Oxytocin
      • Prolactin
      • Growth hormone (GH)
    • Tropic hormones are hormones that target other endocrine glands.
      • Thyroid-stimulating hormone (TSH)
      • Adrenocorticotropic hormone (ACTH)
      • Luteinizing Hormone (LH)
      • Follicle-stimulating hormone (FSH)
      • growth hormone (GH)
    • Growth hormone can be both tropic and nontropic
  • Blood calcium regulation in humans
    • Blood calcium levels are maintained using feedback regulation
      • When blood calcium levels are low, this causes positive feedback, and the release of PTH
      • When blood calcium levels are high, this causes negative feedback, and the release Calcitonin
  • Stress response in vertebrates
  • Overview of gonadal sex hormones
    • Hormones of the testes
      • Androgens: Supports sperm formation;promotes development and maintenance of male secondary sex characteristics
    • Hormones of the ovaries
      • Estrogens: Stimulates uterine lining growth;promotes development and maintenance of female secondary sex characteristics.
      • Progestins: Promotes uterine lining growth
  • Endocrine disruptors
    • A foreign molecule that interrupts the normal function of a hormone pathway
      • example: DES
        • diethylstilbestrol (DES) was a perscription drug that was given to pregnant women who were at risk of having complications (between 1938 and 1971)
        • Daughters of women who took DES tended to have more reproductive abnormalitites, such as vaginal and cervical cancer, structural changes in reproductive organisms, and increasked risk of miscarriage.