ENDOCRINE SYSTEM

• ENDOCRINE SYSTEM:

  • Composed of glands and cells that secrete hormones
  • Helps coordinate functions between cells
  • Critical for maintaining homeostas
• Endocrine System helps regulate:

  • growth and development
  • metabolism and water balance
  • reproduction and stress responses
• Hormones are:

  • Chemical messengers
  • Secreted by endocrine glands or tissues into blood
  • Travel everywhere blood goes
  • Affect only target cells, cells with receptors
  • May affect very distant organs or cells
• Endocrinology:

  • Study of endocrine system
  • Diagnosis and treatment of its disorders
• Functions:

  1.Controls homeostasis

  2. Maintains water balance

  3. Controls uterine contractions

  4. Controls milk production

  5. Regulates ions (calcium, sodium, potassium)
• Exocrine glands - release secretions to tissue by ducts
• Endocrine glands

  • ductless, release into blood
  • other organs not usually considered endocrine glands - e.g., brain and heart, releasing important substances
• Endocrine System:

  • Chemical signals only
  • Slower to respond and stop
  • Hormones go everywhere
  • Adapts relatively slowly
  • Sometimes widespread effects
• Nervous System:

  • Chemical and electrical signals
  • Responds and stops quickly
  • Targets specific organ
  • Adapts quickly
  • Usually local effects
• COMPONENTS OF THE ENDOCRINE SYSTEM

  Endocrine glands - secrete their product directly into blood stream
• COMPONENTS OF THE ENDOCRINE SYSTEM

  Chemical signal - molecules that are released from one location, move to another location, and produce a response
• TYPES OF CHEMICAL SIGNALS

  Intracellular - produce in one of part a cell and move to another part of same cell
• TYPES OF CHEMICAL SIGNALS

  Intercellular - released from one cell and bind to receptors on another cell
• Types of Intracellular Signals

  Autocrine - released by cells and a have local effect on same cell type

  Ex. Eicosanoids (released in response to inflammation)
• Types of Intracellular Signals

  Paracrine - released by cells that affect other cell types in close proximity Ex. Somatostatin (inhibits insulin secretion)
• Types of Intracellular Signals

  Neurotransmitter and neuromodulators - secreted by nerve cells

  Ex. Nervous system function
• Types of Intracellular Signals

  Pheromones - secreted into environment and modify behavior and physiology of other individual in same species Ex. Women and menstrual cycles
• Types of Intracellular Signals

  Hormones and neurohormones: secreted into blood and bind to receptor sites Ex. Epinephrine and insulin
• • Steroid
  • Lipids synthesized from cholesterol
  • Share structure - four organic rings with varied side groups E.g., testosterone and estradiol
• Monoamines

  • Small molecules
  • Synthesized from amino acids tyrosine and tryptophan
  • E.g., thyroxine and epinephrine
• Peptide Hormones

  • Chains from 3 to more than 200 amino acids
  • Considered proteins if > 50 amino acids
  • Oxytocin, small peptide hormone
  • Insulin, a protein
• Hormone receptor

  • Given hormone: fits receptor like key fits lock
  • Insulin “key”: fits only insulin receptor “lock”
  • does not stimulate other receptor types
  • Cell only responds if has proper receptors
• Peptide hormones and most monoamines

  • Hydrophilic, unable to pass into target cell
  • Bind to receptor at cell surface
  • Hormone, first messenger
• Receptor associated with membrane enzyme

  • respond by producing second messenger inside cell
  • often cyclic adenosine monophosphate (cAMP)
• Cyclic AMP

  • Made by removing two phosphates from ATP
  • Activates or reactivates cytoplasmic enzymes
• Cyclic AMP

  Leads to various metabolic effects:

  • e.g., wake up certain genes, producing new enzymes
  • e.g., change permeability of plasma membrane
  • e.g., glucagon activating certain metabolic pathways
• Steroid hormones

  • Hydrophobic, readily pass into cell
  • Bind receptor associated with DNA
  • Causes gene to be transcribed
  • Specific protein produced (alters metabolism in various ways)
• Components of Hormones

  Receptor site - location on a cell where hormone binds (lock)
• Components of Hormones

  Target tissues - group of cells that respond to specific hormones
• Components of Hormones

  Specificity - specific hormones bind to specific receptor sites
• Components of Hormones

  How does this work?

  1. Hormones are secreted by endocrine glands directly into bloodstream

  2. Hormones travel to all parts of body 3. Hormones (key) bind to receptor site (lock) on target tissue 4. Response occurs
• How do hormones cause change?

  1. Alter cell activity of target tissues by increasing or decreasing cell’s normal processes
  2. Change permeability of cell membrane by opening or closing ion channels
  3. Synthesis of proteins
• Types of Hormones

  Water soluble:

  - includes proteins, peptides, amino acids - most common

  - Ex. Growth hormone, antidiuretic, prolactin, etc.
• Types of Hormones

  Lipid hormones:

  - includes steroids and eicosanoids - Ex. LH, FSH, androgens
• Regulation of Hormones

  • Blood levels of chemicals: Ex. Blood glucose levels (insulin)
  • Other hormones: Ex. TSH signals thyroid gland to release thyroid hormone
  • Nervous system: Ex. Epinephrine and fight or flight response
  • Negative Feedback: tells body when homeostasis is reached
• Pituitary Gland

  • Small gland in brain
  • Controlled by hypothalamus
  • Divided into 2 regions: anterior and posterior
  • Secretes at least 6 hormones
• Anterior Pituitary Gland

  Growth Hormone:

  - Target tissues -most

  - Functions - stimulates growth of bones, muscles, and organs

  - Abnormalities: Too much GH causes giantism Too little GH causes pituitary dwarfism
• Anterior Pituitary Gland

  Thyroid-Stimulating Hormone (TSH):

  - Target tissues: thyroid gland

  - Functions: regulates thyroid gland secretions

  - Abnormalities: Too much TSH, thyroid gland enlarges

  Too little TSH, thyroid gland shrinks
• Anterior Pituitary Gland

  GONADOTROPINS:

  LH (Luteinizing) for females:

  - Target tissue: ovaries

  - Function: promotes ovulation and progesterone production
• Anterior Pituitary Gland

  LH for males:

  - Target tissue: testes

  - Function: sperm production and testosterone