Endocrine System

• Autocrine, released by cells and a have local effect on same cell type. Example eicosanoids
• Paracrine, released by cells that affect other cell types in close proximity. Example: somatostatin
• Neurotransmitter and neuromodulators, secreted by nerve cells
• Hormones and neurohormones, secreted into blood and bind to receptors on target tissues. Example epinephrine and insulin.
• Water-soluble hormones are the most common type or hormone. It includes proteins, peptides, amino acids. Examples growth hormone, antidiuretic, prolactin
• Lipid-soluble hormones include steroids and eicosanoids. Examples, Luteinizing hormone and androgens
• Anterior Pituitary Hormones

  • Growth Hormone
  • Thyroid-Stimulating Hormone (TSH)
  • Luteinizing Hormone
  • Follicle-Stimulating Hormone
  • Prolactin
  • Melanocyte Stimulating Hormone
  • Adrenocorticotrophic Hormone
• Hormones of the Posterior Pituitary

  • Antidiuretic Hormone
  • Oxytocin
• Thyroid Gland Hormones

  • Thyroid hormone
  • Calcitonin
• Thyroid Hormone Disorders

  • Hyperthyroidism
  • Hypothyroidism
• Parathyroid Gland secretes Parathyroid hormone (PTH)
• Adrenal Medulla Hormones

  • Epinephrine
  • Norepinephrine
• Adrenal Cortex Hormones

  • Aldosterone
  • Cortisol
  • Androgens
• Pancreas is a mixed gland, with an exocrine portion and an endocrine portion.
• Alpha cells secrete glucagon, beta cells secrete insulin, and delta cells secrete somatostatin.
• Pancreas Hormones

  • Insulin
  • Glucagon
• Testes hormone is testosterone
• Ovarian Hormones

  • Estrogen
  • Progesterone
• Thymus Gland Hormone

  • Thymosin
• Pineal Gland Hormone

  • Melatonin
• Endocrine System Glands

  A) Hypothalamus

  B) Pituitary

  C) Thyroid

  D) Thymus

  E) Adrenals

  F) Ovaries

  G) Testes

  H) Pancreas

  I) Parathyroids

  J) Pineal

  
• Endocrine glands and cells secrete minute amounts of chemical messengers called hormones into the bloodstream, rather than into a duct.
• Hormones travel through the general blood circulation to target tissues or effectors.
• The target tissues have receptors for a specific hormone.
• Control of Hormone Secretion

  • Blood-borne chemicals can directly stimulate the release of some hormones.
  • These chemicals are referred to as humoral stimuli because they circulate in the blood,
• Control of Hormone Secretion

  • The same three types of stimuli (humoral, neural, and hormonal) can stimulate or inhibit hormone release.
• Control of Hormone Secretion

  • Humoral refers to body fluids, including blood
• Control of Hormone Secretion

  
  

  Hormone release can also be under neural control
• Control of Hormone Secretion

  • Following action potentials, neurons release a neurotransmitter into the synapse with the cells that produce the hormone.
• Control of Hormone Secretion

  • Hormone release can also be controlled by other hormones.
  • It occurs when a hormone is secreted that, in turn, stimulates the secretion of other hormones.
• Inhibition of Hormone Release

  • Humoral inhibition of hormone release generally involves the actions of companion hormones.
  • Usually each of the companion hormones performs an opposite function.
• Inhibition of Hormone Release

  • For example, to raise blood pressure, the adrenal cortex secretes the hormone aldosterone in response to low blood pressure, but to lower it the heart atria secrete atrial natriuretic peptide.
  • They work together to maintain homeostasis of blood pressure.
• Inhibition of Hormone Release

  • Neurons inhibit targets just as often as they stimulate targets.
  • If the neurotransmitter is inhibitory, the target endocrine gland does not secrete its hormone.
• Inhibition of Hormone Release

  • In control of hormone release by other hormones, some hormones are inhibitory hormones, that reduce the release of the hormone being controlled.
  • For example, thyroid hormones can control their own blood levels by inhibiting their anterior pituitary tropic hormone.
• Regulation of Blood Hormone Levels

  
  

  Two major mechanisms maintain hormone levels in the blood within a homeostatic range: negative feedback and positive feedback
• Hormone Receptors and Mechanisms of Action

  
  

  A hormone can stimulate only the cells that have the receptor for that hormone.
• Hormone Receptors and Mechanisms of Action

  
  

  The portion of each receptor molecule where a hormone binds is called a receptor site.
• Hormone Receptors and Mechanisms of Action

  • The receptor site has specificity, allowing only one hormone to bind to it.
  • Some hormones, such as epinephrine, can bind to a “family” of receptors that are structurally similar.
  • This specificity is due to molecular shape and chemical characteristics.
• Hormone Receptors and Mechanisms of Action

  
  

  Lipid-soluble and water-soluble hormones bind to their own classes of receptors.
• Lipid-Soluble Hormone Receptors

  • Nuclear receptors can also be located in the cytoplasm, but then move to the nucleus when activated.
  • When hormones bind to nuclear receptors, the hormone-receptor complex interacts with nuclear DNA to regulate specific gene transcription.