Endocrine system

• Communication - Maintenance of homeostasis (maintain communication between body parts)
• Intercellular communication

  
  

  communication btw cells

  • sender/signaler (one creating message to talk to other cells)
  • messenger molecules (used to communicate, uses chemicals to do this)
  • recipient/target (who gets the message)
  • receptor (protein, receives message)
• Local intercellular communication:

  Direct communication and Paracrines
• Direct communications:

  physical communication

  gap junctions

  cytosol
• Paracrines:

  chemical message released by exocytosis

  extracellular fluid/interstitial fluid (once released message diffuses to reach its target)
• Long-distance intercellular communication:

  synaptic communication and endocrine
• Synatptic communication:

  action potential and axon

  exocytosis

  neurotransmitter (is the message molecule between something and its target)
• Endocrine:

  exocytosis (uses exocytosis to send message)

  circulatory system (message goes into, not a direct line/not fast, message happens for long periods of time)

  hormone (message molecule)
• Communication:

  Endocrine system

  • glands and specialized groups of cells
  • endocrine vs. exocrine
  • hormones
  • effects (three different)
  • stimulate protein synthesis (make new proteins)
  • increases/decrease rate of protein synthesis
  • alter activity of existing protein (not affection transcription/lation, turning proteins on/off → affection enzymatic rates)
• Hormones:

  a chemical substance that has an action on a particular cell type

  • target may be far away from source

  bind to a receptor at the target cell

  • number of receptors may vary with time
  • up-regulation (trying to increase # of receptors)
  • more sensitive (more receptive, more likely to receive message)
  • down-regulation (decrease # of receptors)
  • less sensitive

  (receptor need for hormone to interact with target)
• Chemical Classifications:

  amino acid derivatives

  peptides

  lipid derivatives
• Amino acid derivatives:

  tyrosine

  • thyroid hormones
  • catecholamines: epinephrine, norepinephrine, dopamine

  tryptophan

  • melatonin
• Peptides:

  chains of amino acids

  glycoproteins: TSH, LH, FSH (smaller than typical proteins)

  short polypeptides: ADH, growth hormone
• Lipid derivatives:

  eicosanoids (chemical messages used in immune system → pain, allergies) : prostaglandins and leukotrienes (pain pathways)

  steroid hormones: estrogen, testosterone, corticosteroids (stress)
• Receptor location: cell surface/membrane (receptor protein on the cell membrane)

  water soluble (enter bloodstream to go to target)

  • catecholamines, peptides, eicosanoids

  hormone does not enter cell (not lipid-soluble)

  use G proteins and second messengers (g protein creates second message)

  • cAMP, cGMP, Ca+2

  set a cascade of reactions in motion (multiple reactions/series)

  • amplification

  effects

  • alter activity of enzymes already present (turn on/off)
• Receptor location: intracellular

  cytosol or nucleus

  • lipid soluble or transporter (goes across cell membrane)
  • ex: thyroid hormone, steroids
  • effect
  • stimulate synthesis of new proteins
  • alter the rate of protein synthesis
  • increase/decreases
• hormones:

  response of target depends on

  • presence or absence of receptors
  • number of receptors
  • amount of hormone
  • influence of other hormones (interact)
  • permissive (need permission, allowed, hormone A has to be present so hormone B can have effect)
  • synergistic/additive (both hormones work together to create greater affect)
  • antagonistic (trying to stop something, have the opposite effect)
• Hormone secretion:

  regulated by

  • neural stimuli
  • chemical changes in the bod fluids
  • hormonal effects
  • negative feedback
• Hypothalamus:

  located in brain, just below thalamus

  controls autonomic nervous system

  regulates homeostasis

  • temperature, thirst, hunger, fear, anger, sexual behavior)

  secrete regulatory hormones (regulate other endocrine hormones)
• hypothalamus hormones:

  produces 9 hormones

  • 7 affect release of anterior pituitary gland
  • 2 are stored in and released by posterior pituitary gland (made in hypothalamus and transported and stored in pituitary gland)
• Pituitary Gland:

  connected to hypothalamus by infundibulum (piece of tissue)

  composed of 2 parts

  • posterior pituitary
  • anterior pituitary
  • hypophyseal portal system (blood vessels, connects from hypothalamus to pituitary, hormone)
  • 2 sets of capillaries in series
  • direct delivery of hypothalamic hormones
• Anterior Pituitary Gland:

  Secretes seven hormones

  • prolactin (PRL) - affects mammary glands → milk production
  • Melanocyte Stimulating hormone (MSH)
  • Human growth hormone - affects growth, miniatous of bones and muscles
  • Thyroid stimulating hormone (TSH) - release thyroid hormones
  • Follicle stimulating hormone (FSH) -
  • Leutenizing hormone (LH)
  • Adrenocotropin hormone (ACTH)
• Posterior Pituitary Gland:

  Does not produce own hormones

  2 from hypothalamus

  • oxytocin - target is smooth muscle of reproductive tract, ex: child birth
  • positive feedback
  • Antidiuretic hormone (AH)/vasopressin - target → kidneys, water conservation/retention
• Pineal gland:

  located in the diencephalon

  Melatonin (target → brain)

  • affected by light levels
  • levels increases in the dark
  • sleepy
  • levels decrease in the light
  • alert
  • responsible for circadian rhythms
• Thyroid gland:

  located in throat, in front of larynx

  Hormones: Thyroxine (T4) and T3 (two forms, # of iodines)

  • follicle cells - thyroglobulin (made by follicle cells)
  • iodine (needed to make hormones
  • Involved in the regulation of
  • increases metabolic rate - calorigenic effect (metabolism generates heat, maintains body temp)
  • Production of Na+/K+ ATPase
  • Increase effect of catecholamines
  • growth and development
• Thyroid Hormone: Calcitonin

  C cells

  regulates Ca+2 levels in blood

  promotes the addition of Ca+2 to bone

  • decreases blood calcium
  • (present when high levels of calcium in blood)
• Parathyroid Glands:

  Posterior surface of thyroid

  • four pea sized glands

  Parathyroid hormone

  • increases blood Ca+2 (antagonistic to calcitonin)
  • release of Ca+2 from bone
  • increase Ca+2 absorption in kidney
  • promotes release of calcitriol
  • active form of vitamin D
  • Increase Ca+2 absorption by gut (helping body absorb calcium from diet)
• Thymus Gland:

  Located in throat area, just below larynx

  thymosins (chemical messages)

  • major role is maturation of lymphocytes
  • may slow when aging
  • more active in juveniles
• Adrenal glands:

  located above each kidney

  composed of 2 section

  • adrenal cortex (outer)
  • adrenal medulla (inner)
• Adrenal cortex:

  Outside Layer

  Mineralocorticoids (steroid hormone) - water and salt balance

  • aldosterone - main one, targets kidneys, helps retain ions and water

  Glucocorticoids - stress hormones (help body deal with stress)

  androgens - sex hormone
• Adrenal medulla:

  Epinephrine and norepinephrine

  • fight of flight response
  • mobilization of glucose for ATP production
• Pancreas:

  Endocrine and exocrine functions

  • exocrine: digestive enzymes
  • endocrine
  • glucagon: increase blood sugar (/glucose) levels (alpha cells) (causes body to release stored glucose levels
  • Insulin: stimulates cells to take to glucose; lowers blood sugar (beta cells)
  • Stomatostatin: growth hormone-inhibiting hormone (delta cells, antagonist of growth hormone)
  • Pancreatic peptide (hormone): regulates pancreatic secretion (F cells)
• Gonads:

  produce sex hormones

  production of gametes

  ovaries and testes
• Ovaries:

  located in the pelvic cavity

  female reproductive cycle, pregnancy, lactation

  estrogen and progesterone - two primary hormone

  inhibin and relaxin - hormones produced in small quantities, help with pregnancy
• Testes:

  Located outside body, in scrotal sac

  male characteristics and sperm development

  testosterone