Topic 78 - Hormones from the neurohypophysis

Question 1

Words to include

Answer 1

• Hypophysis
  
  • Neurohypophysis (posteror lobe)
  • Adenohypophysis (anterior lobe)
• Hypothalamus
• Ectodermal nervous tissue
• Hypothalamus
• Mangocellular hormones
• Oxytocin
  
  • Uterus
  • Labor contractions
  • Estrogen response
  • Basket cell contraction (myoepithelial cells)
  • Classical neuroendocrine reflex
    
    • Neuroendocrine reflex arch
      
      • Neural information
      • Peripheral sensory nerve
      • Endocrine system
      • Hypothalamus
    • Milk ejection
      
      • Udder-nipple afferent sensory fibers
      • Spinal cord
      • Inguinal nerve
      • Mammary gland
      • Blood circulation
      • Myoepithelial cells (basket cells)
• Vasopressin / ADH (Antidiuretic Hormone)
  
  • Kidney
  • Water loss
  • Water uptake
  • Water absorption
  • Water reabsorption
    
    • Distal tubules
    • Collecting ducts
    • V2 receptor
    • cAMP
  • Water storage
  • Urine
  • Dehydration
  • Blood pressure (↑)
  • V1 receptor
  • IP3 (vasoconstriction)

Question 2

General about the neurohypophysis

Answer 2

• The hypophysis is separated into two parts:
  
  • Neurohypophysis (posterior lobe)
    
    • Mangocellular hormones
  • Adenohypophysis (anterior lobe)
• The neurohypophysis is an extension of the hypothalamus, and it is developed from the ectodermal nervous tissue during embryonic life
• Oxytocin and vasopressin (ADH) are hormones that are produced in the hypothalamus, but are stored and secreted from the neurohypophysis

Question 3

Give the hormones of the neurohypophysis

Answer 3

1. Oxytocin
2. Vasopressin / ADH (Antidiuretic Hormone)

Question 4

Oxytocin and vasopressin, general

Answer 4

Question 5

Oxytocin

Answer 5

• Stimulates the uterus, especially during late pregnancy and birth
• During birth oxytocin helps keep the strength of the labor contractions
• You can give oxytocin to “activate” labor
• The production of oxytocin will also be stimulated by the breastfeeding of the baby
• Preparation of uterine contractions for estrogen response
• Basket cell contraction (myoepithelial cells)
• Classical neuroendocrine reflex
  
  • Oxytocin mechanism is a neuroendocrine reflex
    
    • Co-operation of neural and endocrine systems
  • Neuroendocrine reflex arch:
    
    1. Translation of neural information, originated from the peripheral sensory nerve, to the language of the endocrine system with the help of hypothalamus
    2. Effect/respones is hormonal (not neural)
  • Precondition of milk ejection:
    
    1. Excitation from udder-nipple afferent sensory fibers reaches the spinal cord by the inguinal nerve
    2. Excitation arrives at the hypothalamus, where an enhanced oxytocin synthesis is evoked
    3. Oxytocin release increases from the posterior lobe of the pituitary gland
    4. Oxytocin reaches mammary gland with the blood circulation, where it elicits contraction of the myoepithalial cells (basket cells)

Question 6

Vasopressin / ADH

Answer 6

• Functions on the kidneys, helps regulate the loss of water by regulating the uptake of water from the urine
  
  • Stimulates the water reabsorption in:
    
    • Distal tubules
    • Collecting ducts
    • V2 receptor
    • cAMP
• This will also help reduce the level of urine
• Dehydration will be very stimulating for vasopressin, because of the huge need for water absorption and storage
  
  • If the vasopressin secretion were to be inhibited the amount of urine would be doubled almost 10 times
• Effect:
  
  • Increase of blood pressure
  • V1 receptor
  • IP3 (vasoconstriction)
• Amino acid: 9