GENBIO2 M9-M10

• Animal Hormones


  Chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body
• Animal Hormones


  • Reach all parts of the body
  • Only target cells have receptors for that hormone
  • Controlled by the Endocrine System
  • Nervous and endocrine systems often overlap in function
• Signaling of neurons influence the release of hormones

  Paracrine and Autocrine Signaling play roles in processes such as blood pressure regulation, nervous system function, and reproduction
• Prostaglandins


  Local regulators that mediate paracrine and autocrine signaling
• Prostaglandins


  • Function in reproduction
  • Function in the immune system
  • Function in blood clotting
  • Function in pain response
• Endocrine Signaling


  Hormones secreted into extracellular fluids by endocrine cells reach their targets via the bloodstream
• Endocrine Signaling


  • Maintains homeostasis
  • Mediates responses to stimuli
  • Regulates growth and development
• Synaptic Signaling


  Neurons form specialized junctions with target cells, called synapses
• Neurotransmitters


  Molecules secreted by neurons at synapses that diffuse short distances and bind to receptors on target cells
• Neuroendocrine Signaling


  Specialized neurosecretory cells secrete molecules called neurohormones that travel to target cells via the bloodstream
• Local regulators


  Molecules that act over short distances, reaching target cells solely by diffusion
• Paracrine signaling


  Target cells lie near the secreting cells
• Autocrine signaling


  Target cell is also the secreting cell
• Pheromones


  Chemicals released into the environment used by members of an animal species to communicate
• Pheromones


  • Marking trails leading to food
  • Defining territories
  • Warning of predators
  • Attracting potential mates
• Classes of Local Regulators

  Prostaglandins are modified fatty acids<|>Others are polypeptides and some are gases
• Nitric oxide (NO)


  A gas that functions in the body as both a local regulator and a neurotransmitter
• When the level of oxygen in blood falls


  NO activates an enzyme that results in vasodilation, increasing blood flow to tissues
• Multiple Effects of Hormones

  The same hormone may have different effects on target cells that have different receptors for the hormone or different signal transduction pathways
• Classes of Hormones


  • Water-soluble (hydrophilic)
  • Lipid-soluble (hydrophobic)
  • Polypeptides
  • Steroids
  • Amines
• Water-soluble hormones


  • Secreted by exocytosis
  • Travel freely in the bloodstream
  • Bind to cell-surface receptors
• Lipid-soluble hormones


  • Diffuse across cell membranes
  • Travel in the bloodstream bound to transport proteins
• Endocrine Tissues and Organs

  Endocrine glands are ductless organs such as the thyroid and parathyroid glands, testes, and ovaries
• Exocrine glands


  Glands such as salivary glands that have ducts to carry secreted substances onto body surfaces or into body cavities
• Simple Hormone Pathways


  Hormones are released from an endocrine cell, travel through the bloodstream, and interact with specific receptors within a target cell to cause a physiological response
• Negative feedback


  Inhibits a response by reducing the initial stimulus, thus preventing excessive pathway activity
• Positive feedback


  Reinforces a stimulus to produce an even greater response
• Posterior Pituitary Hormones


  Neurosecretory cells of the hypothalamus synthesize the two posterior pituitary hormones: Antidiuretic hormone (ADH) and Oxytocin
• ADH


  • Regulates physiology and behavior
  • Increases water retention
• Oxytocin


  • Regulates milk secretion by the mammary glands
  • Regulates uterine contraction during birthing
• Prothoracicotropic hormone (PTTH)


  Produced by neurosecretory cells in the larval brain, controls the molting of larva
• PTTH


  • Directs the release of ecdysteroid
  • Bursts of ecdysteroid trigger each successive molt as well as metamorphosis
• Metamorphosis


  Not triggered until the level of another hormone, JH (juvenile hormone), drops
• Anterior Pituitary Hormones


  Controls hormone production in the anterior pituitary using releasing hormones and inhibiting hormones
• Anterior Pituitary Hormones


  • FSH and LH stimulate ovaries and testes
  • TSH stimulates thyroid gland
  • ACTH stimulates adrenal cortex
  • Prolactin stimulates mammary gland cells
  • GH stimulates growth and metabolic functions
• Oxytocin


  • Stimulates contraction of smooth muscle cells in uterus and mammary glands
• Vasopressin (ADH)


  • Promotes retention of water by kidneys
  • Influences social behavior and bonding
• Thyroid hormone (T3 and T4)


  Stimulates and maintains metabolic processes
• Calcitonin


  Lowers blood calcium level
• Parathyroid Hormone (PTH)


  Stimulates Ca²+ release and uptake, promotes activation of vitamin D